BAB Anatomy

Which descending pathways are ventromedial, innervating proximal extensors and axial muscles for posture?

Tectospinal, vestibulospinal, pontine(medial)&medullary(lateral) reticulospinal

What structures make up the forebrain and what is their embryological origin?

Telencephalon=cerebral cortex. Diencephalon=thalamus, subthalamus, hypothalamus, epithalamus(contains pineal gland)

What does the lateral sulcus separate?

Temporal lobe (superior temporal gyrus) from frontal and parietal lobes

How can the spindle stretch reflex be used in clinical examination?

Tendon reflexes/jerks. Hammer tendon of the muscle, causing brief stretch. Absent reflex indicates level of LMN lesion Jaw=CN Vc (mandibular branch) Biceps=C5/6 (musculocutaneous n afferent and efferent) Brachioradialis=C5/C6 (radial) Triceps=C6/C7 (radial) Quadriceps (patellar tendon/knee jerk)=L3/L4 (femoral) Achilles tendon=S1/S2 (tibial)

What do golgi tendon organs sense? Outline their reflex pathway:

Tension in tendon when muscle contracts. Polysynaptic pathway: GTO in in tendon, in series with the muscle. Muscle contraction->firing of Ib afferents to inhibitory interneurone in cord->suppression of alpha efferent, causing muscle relaxation. Prevents damage, allows for fine movement

Describe the acoustic/attenuation reflex:

Tensor tympani(Vc) and stapedius(stapedius branch of VII) contract in response to loud noise, holding the auditory ossicle rigid, inhibiting their vibration, reducing their amplification of the sound waves. For protection, adapting to loud sounds and small role in recognising high freq sounds

What dural reflection forms the roof and lateral walls of the cavernous sinus (drains the opthalmic vein)? What are its attachments?

Tentorium cerebelli. Attaches anterolaterally to petrous part of temporal bone, and anteriorly at ant&posterior clinoid processes of sphenoid, forming inferior and superior petrosal sinuses

Course of the general somatic afferents of facial nerve from the EAM?

Terminate in the trigeminal sensory nucleus -> secondary neurone runs in trigeminothalamic tract

Where do the optic tracts synapse with secondary neurone? Exception?

The 2 optic tracts diverge from each other and pass round the crus cerebri/peduncle to lateral geniculate nucleus of thalamus. Exception are few fibres which branch off before reaching thalamus to go to pre-tectal area and synapse with neurones in Edinger-Westphal for accomodation and light reflexes

Where is the sensory association area?

The cortex immediately posterior to the somatosensory cortex in the superior parietal lobe. Involved in mental functions more complex than just detecting basic dimensions of sensory stimuli

What is the sclera a continuation of, as the outermost layer of the eye? What does it form on the anterior pole of the eye?

The dura mater surrounding the optic nerve. Attaches to the extraocular muscles. Forms transparent cornea anteriorly to allow light to enter

What are the crus cerebri continuous with superiorly? What are they formed of?

The internal capsule. Motor corticospinal and corticobulbar fibres. (interpeduncular fossa spearates the crura)

What is meant by the term 'reticular activation system?'

The parts of the brain responsible for arousing a more awake and alert state. Reticular formation is a large component, integrating and projecting ascending info.

What types of vascular disorder can have consequences in the brain?

Thrombosis(vessel occlusion), infarction(restriction of the blood and oxygen supply), haemorrhage (bleeding into nervous tissues)

Difference between thrombus and embolus?

Thrombus= product of platelet aggregation and fibrin production in response to endothelial damage Embolus= thrombus/air bubble/fat deposit carried in blood and lodged in distal vessel

Where do the 3rd order thalamocortical neurones project from lateral geniculate nucleus?

Through internal capsule, forming OPTIC RADIATION->terminates in primary visual cortex in occipital lobe(either side of calcarine sulcus)

What forms the blood-brain barrier?

Tight junctions between endothelial cells in the cerebral BVs. Supported by astrocytic and pericytic foot-like processes.

Summarise the main outputs from the cerebellum:

To reticular formation, vestibular nuclei(influencing vestibulospinal tract), cortex(influencing corticospinal&corticobulbar), red nucleus(influencing rubrospinal), ventral lateral nucleus of thalamus(in main excitatory loop)

Describe the myotatic stretch reflex, explaining the concept of reciprocal inhibition.

monosynaptic, 2 neurone arc. Muscle spindles contain intrafusal muscle fibres in parallel with the muscle. Detect stretch magnitude and rate of change->increased activity in Ia/II sensory afferent which bifurcates in cord. One branch synpases with alpha MN efferent, which causes muscle contraction of extrafusal fibres to maintain posture and prevent overstretching. Other branch synapses with inhibitory interneurone connected to MN of antagonistic muscle=reciprocal inhibition of contraction

How is flexion of a whole limb about several joints coordinated in a GTO reflex?

more than one spinal segment's circuitry involved through collateralisation of primary afferents and interneurones

What is coma and how is coma defined by the GCS?

Total absence of awareness of self and external environment, unarousable unconsciousness. Gross impairment of both cerbral hemispheres diffusely, or ARAS/brainstem Score <9 (3-8)

Describe the somatotropic organisation of the descending tracts?

Tracts to cervical regions closer to midline

What is the tympanic membrane formed from? What does it separate?

Translucent double layer of skin and mucous membrane. Between outer and middle ear

What sinuses are contained in the tentorium cerebelli?

Transverse sinuses(running laterally round occipital lobe), superior and inferior petrosal sinuses(drain the caverous sinus, into the IJV)

Which are the 6 paired sinuses? How many unpaired dural sinuses are there?

Transverse, sigmoid, cavernous, greater and lesser petrosal, sphenoparietal. 6 unpaired(superior and inferior sagittal, straight, occipital, confluence)

Where are the cell bodies of the trigeminothalamic primary afferents? What is the exception?

Trigeminal ganglion(equivalent to the DRG for spinal afferents) , in Meckel's cave(cavity lined by dura in petrous part of temporal bone). Exception are the proprioceptive primary neurones, whose cell bodies are in the mesencephalic nucleus of the trigeminal nerve - only situation where peripheral cell body is in the CNS

Which sensory nucleus is associated with general somatic afferents?

Trigeminal sensory nucleus. 3 subnuclei from rostral to caudal: -mesencephalic= proprioception(cell bodies IN the CNS) -chief sensory=touch and pressure -spinal nucleus of trigeminal=pain and temp V(GSA from face and head), VII(GSA from EAM), IX(GSA from oropharynx, carotid sinus and body), X(GSA from laryngopharynx, larynx, aortic bodies, thoracic and abdo viscera)

Which nerve is the main sensory nerve for the head but also has a small motor component to muscles of mastication(and tensor tympani, tensor veli palatini, ant belly digastric and mylohoid)?

Trigeminal. Arises from ventrolateral pons where it merges with middle cerebellar peduncle as 2 roots (larger sensory and smaller motor). Nuclei of the trigeminal afferents (opthalmic, maxillary, mandibular) lie in trigeminal ganglion except proprioceptive afferents(mesencephalic nucleus)

Describe the course of the trochlear nerve. Where is the trochlear nucleus that it arises from?

Trochlear nucleus at base of PAG at level of inferior colliculus. Axons pass dorsally round PAG and cross each other in midline. Emerge just below the inferior colliculus(on dorsal side of pons) and course round to ventral side round th cerebral peduncles. Then follows almost same course as CN III, through laterall walls of cavernous sinus, exiting through SOF

What is an uncal herniation?

Type of transtentorial herniation where uncus of temporal lobe is pushed through tentorial notch, notably compressing the midbrain->ipsilateral dilated pupil (ipsilateral CN III compressed)->ipsilateral hemiplegia (contralateral brainstem compressed)->ipsilateral tetraparesis->erratic respiration->death.

What is a central herniation? What can it progress to?

Type of transtentorial. Herniation of diencephalon and parts of both temporal lobes through tentorial notch in midline, compressing midbrain, then pons, then medulla. May progress to coning(cerebellar tonsil herniation, stiff neck).

Course of the corticospinal pathway?

UMN cell body in pre-central gryus(M1) (Betz cells give largest diameter UMNs in the tract), through corona radiata and internal capsule, midbrain crus cerebri, ventral pons (can see fascicles of the fibres in horizontal section) and medulla where they form the medullary pyramids. ->majority decussate to join contralateral lateral tract and synapse in ventral horn at ALL cord levels. Minority stay ipsilateral and join ventral tract, decussate near their synpase in cervical and upper thoracic segments

Outline the course of the UMN and LMN for the hypoglossal nerve (CN XII):

UMN decussates in medulla and terminates in CONTRALATERAL hypoglossal nucleus in medulla. LMN innervates muscles of tongue, so innervation is UNILATERAL

Explain the fore-head sparing seen in UMN lesion of the facial nerve:

UMN for temporal branches synapse in upper part of ipsilateral and contralateral facial motor nuclei UMN for zygomatic, buccal, marginal mandibular and cervival branches synpase in lower part of CONTRALATERAL facial motor nucleus. As innervation is bilateral for the forehead and orbicularis oris etc (innervated by temporal branch), forehead is spared and spastic contralateral muscle weakness below forehead is seen.

Outline the course of the UMN and LMN for CNs III,IV,V,VI,IX,X,XI:

UMN from lateral M1 terminates in both contralateral and ipsilateral CN motor nuclei as only some decussate. Innervation BILATERAL so UMN lesion will cause weakness of muscles on both sides and LMN lesion will cause complete paralysis on the corresponding side

Describe the corticobulbar tract's course. What does it innervate?

UMN from lateral primary motor cortex, through genu of internal capsule to brainstem and terminates on motor nuclei of the cranial nerves. (the motor CN fibres innervate head and neck muscles of somatic and pharyngeal arch origin)

Course of vestibulospinal tracts?

UMN from vestibular nuclei in pons(lateral) or medulla(medial). Descend ipsilaterally (lateral in ventral funiculus)->synapse in ventral horn

Path of the reticulospinal tracts? (pontine and medullary)

UMN in pontine or medullary reticular formation, descends ipsilaterally (pontine medial, medullary lateral) ->synapse in ventral horn

How may we observationally distinguish between a UMN and LMN lesion?

UMN: hyperreflexia, spasticity, present Babinksi reflex, weakness/paralysis of specific movements, disuse atrophy LMN: fasciculations, hyporeflexia, hypotonia(reduced resistance to passive stretching), weakness of myotome of the specific nerve root, denervation atrophy

Where do the cells in the ventral horn receive inputs from?

UMNs in descending pathways from higher centres, and certain dorsal root afferents (reflexes)

Course of the rubrospinal tract?

UMNs originate from red nucleus of midbrain tegmentum and decussate (ventral tegmentum decussation) and descend in lateral funiculus ventrolateral to lateral corticospinal tract. Synpase in ventral horn laminae V,VI or VII

What is CSF?

Ultrafiltrate of plasma: protein-free and higher concentrations of Na, K, Mg and glucose. No RBCs, few WBCs.

Which tests can indicate a midline cerebellar lesion?

Unable to stand in Romberg test with eyes open or closed

Common causes of upper and lower MN lesions?

Upper= stroke, MS, brain trauma, cerebral palsy Lower= ischaemia, trauma(laceration or compression), MND, Guillian-Barre

How does Rinne's test distinguish between conductive and sensorineural hearing loss?

Uses difference in bone and air conduction of vibrations. Vibrating tuning fork placed on mastoid process(bone conduction) and then close to auricle(air conduction). Normal= conduction in air>conduction in bone (hear it for 2x as long in air) Conductive loss= bone> or = air conduction time Sensorineural loss= conduction in bone>in air

Which CNs are a mixture of sensory and motor?

V(sensory from head and face, Vc is partly GSE to muscles of mastication, tensor tympani and tensor veli palatini) VII(SVA from ant2/3 tongue, GSA from skin in external auditory meatus and bit of tympanic membrane, GVE to superior salivatory nucleus->submandibular and sublingual glands, SVE to muscles of pharynx, larynx, muscles of facial expression IX(GSA from oropharynx and carotid sinus&body, SVE from posterior 1/3 tongue, GVE to inf. salivatory nucleus->parotid, SVE to stylopharyngeus)

Which CN innervates muscles derived from the 1st pharyngeal arch?

V3(mandibular) = muscles of mastication, tensor tympani, tensor veli palatini, anterior belly digastric, mylohyoid

Effects of the paralysis of affected CNs in Locked-in syndrome?

V=mastication issues, IV=lose superior oblique(can't move eye inferolaterally), VI-lose lateral rectus, VII=facial paralysis, IX(&X stylopharyngeus)=dysphagia, X=aphonia(recurrent laryngeal)-tracheostomy otherwise asphyxiation due to vocal cord adduction, XII=anarthria, tongue paralysis

Which CNs pass through internal acoustic meatus in temporal bone?

VII, VIII

Names of the other branches of the subclavian artery?

VITDC vertebral, internal thoracic, thyrocervical, dorsal scapular, costocervical

What is the tegmentum of the midbrain?

Ventral portion, forming floor of midbrain, surrounding cerebral aqueduct. Bounded anteriorly by crus cerebri(anterior portion of cerebral peduncles). Occupied by structures between cerebral aqueduct and substantia nigra(see in horizontal section) in horizontal section(red nucleus, rostral end of reticular formation, substantia nigra)

Pathways of each spinocerebellar tract?

Ventral: Cell body in DRG. Synapse with secondary in dorsal horn - some decussate through ventral white commissure, ascend & enter cerebellum via superior cerebellar peduncle. Decussate in cerebellar white matter (double cross) to end up ipsilateral. Other just ascends ipsilaterally, passing through superior cerebellar peduncle, then synapsing. Dorsal: Primary cell body in DRG. Synpase with secondary whose cell body is in Clarke's column in dorsal horn. Stays ipsilateral and ascends to cerebellum via INFERIOR cerebellar peduncle

Which sensory nuclei are associated with special somatic afferents?

Vestibular and cochlear nuclei. Between trigeminal sensory laterally and NTS medially) II(sight) and VIII(hearing, balance)

How does CN VIII contribute to motor output?

Vestibular nerve to vestibular nuclei-> relays to descending fibres of the vestibulospinal tract in the medial longitudinal fasciculus, to help maintain head and neck in position. Some fibres also go to vestibulo-cerebellum for equilibrium. (some fibres from CN III,IV,VI nuclei contributes sensory input to tectospinal tract in median longitudinal fasciculus to keep gaze forward when head moves quickly)

The two parts of the vestibular nerve?

Vestibular(balance), cochlear(hearing). Pass together through IAM(as well as CN VII), attach to brainstem at cerebello-pontine angle at ponto-medullary junction.

How does CSF bathe the brain?

Via cisterns (openings in pia and arachnoid mater) allowing CSF from 4th ventricle to flood the subarachnoid space. Fron subarachnoid space->blood via arachnoid granulations

How does papillaedema present and what causes it?

Vision blurring, enlargement of blind spot, visual obscurations. -> vision loss Cause= optic disc swelling(often bilateral) due to incr ICP

How is our visual field represented onto our retina(1/4s)?

Vision from temporal field forms image on nasal half of retina and vision from nasal field forms image on temporal half of retina. Lower half of visual field forms image on upper half of retina, and upper half of visual field on lower half of retina

What forms the subarachnoid space?

Web-like trabeculations of arachnoid mater into the space between arachnoid and pia mater. Contains CSF and all major BVs supplying brain and CSF

At what value does intracranial pressure start impeding perfusion to brain tissue? How does raised ICP present?

When cerebral perfusion pressure falls to 60mmHg (CPP = ABP - ICP). Hypertension, bradycardia, respiratory irregularity

Where do lower MN cell bodies lie?

Where they synapse with UMN from cortex or other higher centre, in ventral horn of spinal cord, or a motor nucleus of a CN

Outline the neuro exam involving whispering and making masking sounds with your fingers and thumb. How does this detect hearing loss?

Whisper lists of words to be repeated 2ft away from each ear and rub finger and thumb together to make masking sound. In both types of hearing loss there will be reduced sound conduction

How is the cerebellar medulla arranged?

White matter axons of afferens and efferents. 4 pairs of deep cerebellar nuclei, the largest=dentate nuclei.

Gross appearance of the brain in vascular dementia?

Wider sulci due to neuronal atrophy (small brain)

Where is the middle ear located? Contents?

Within temporal bone, from tympanic membrane to inner ear. Contains tympanic membrane, 3 auditory ossicles(malleus attached to tymp membrane, incus, stapes attached in oval window of inner ear).

Where is Clarke's column?

aka nucleus dorsalis, C8-L3. Deep in dorsal horn(lamina VII). Cell bodies of primary dorsal spinocerebellar tract neurones, receiving signals from spindles, GTOs, tactile and pressure receptors

What is the sensory homunculus?

neurological mapping of sensory input from the anatomical divisions of the body on the sensory cortex. Uneven distribution, reflecting the differential sensitivities of different body parts and our ability to discriminate finer levels of sensation

Most common site of aneurysm in the Circle of Willis network?

anterior communicating artery, where it junctions with either of the anterior cerebral arteries

Names of the 3 semicircular canals?

anterior)superior), posterior and lateral(horizontal). Contain perilymph, detect rotational acceleration

How are the signs of LMN lesion of CNXII different?

atrophy, fasciculation and paralysis of tongue ipsilateral to lesion (tongue deviates TOWARDS side of lesion)

Sensory innervation of the EAM?

branches of CN Vc, VII and X

What does lamina IX in the ventral horn correspond to?

cell bodies of: alpha MNs innervating extrafusal muscle fibres, gamma MNs innervating intrafusal muscle fibres. (well-developed in cervical and lumbar enlargements)

Which branches does the ICA give off in the opthalmic segment following its siphon?

coursing parallel to optic nerve(CN II), gives off hypophyseal branch(pituitary) and opthalmic branch(eye, orbital structures, frontal&ethmoid sinuses)

Examples of facial muscles innervated by CN VII terminal motor branches?

(divides into 5 at parotid gland) Temporal: bilateral to frontalis, orbicularis oculi, corrugator Zygomatic: orbicularis occuli Buccal: orbicularis oris, buccinator, nasalis, zygomaticus, levator labii superioris Marginal mandibular: mentalis, depressor labii inferioris Cervical: platysma

What are the superior colliculi?

(part of midbrain tectum). Relay input from the optic tract to the lateral geniculate nuclei of the thalamus

What 5 branches are given off by each vertebral artery?

- 1x Anterior spinal artery (formed by fusion of a branch off each vertebral artery)->descends through foramen magnum on anterior spinal cord -2x Posterior spinal arteries(may originate off the PICA)->descend through f magnum on posterior spinal cord -PICA(posterior inferior cerebellar artery)->largest branch passing posteriorly between medulla and cerebellum -Meningeal branches -Medullary branches

What structures do the major branches of the basilar artery supply?

-AICA= ant inf cerebellum -Labyrinthine= contents of IAM and inner ear apparatus -pontine branches= pons -sup cerebellum= upper half cerebellum -posterior cerebral=visual cortex of occipital lobe, inf temporal lobe, thalamus, posterior midbrain, basal ganglia, choroid plexus

Outline the 1st cervical segment of the ICA:

dilates at carotid sinus, runs in carotid sheath with CNX and IJV. Branchless as runs extracranially

What are the 3 components of the GCS?

1. eye opening(spontaneously, to speech, to pain, none) 2. best verbal response(orientated, confused, inappropriate words, incomprehensible sounds, none) 3. best motor response(obeys commands, moves to localised pain, flexion withdrawl from pain, decorticate/abnormal flexion), decerebrate/abnormal extension) Min score=3, max=15

Outline the course of the special visceral afferents of CN VII travelling in the chorda tympani:

1: Carrying taste from ant2/3 tongue->cell bodies in geniculate ganglion in facial canal of petrous part of temporal bone. Synpase in nucleus solitarius. 2: secondary neurone to VPN of thalamus and synapse 3: tertiary to appropriate part of sensory cortex

Course of the dorsal columns?

1: Cell body in DRG, axon to dorsal horn and ascends without synapsing to dorsal medulla. Synapse in nucleus gracilis(medial) or nucleus cuneatus(lateral) in medulla. 2: Secondary neurones decussate in medulla as the internal arcuate fibres and ascends through brainstem as medial lemniscus(fibres from gracilis now running lateral and cuneatus medial) to the VPL in the thalamus to synapse 3: Cell body in VPL, travels through internal capsule to appropriate areas of sensory cortex(arm area is lateral and leg area is medial)

Describe the path of the neurones in the ascending spinothalamic tracts

1: dendron to DRG, axon to synapse at dorsal horn 2: decussates immediately(within one segment) in ventral white commissure. Ascends in SPINAL LEMNISCUS, through PYRAMIDS (medulla), pons and middle of the SUBSTANTIA NIGRA(midbrain) to terminate in VPL nucleus in the thalamus 3: Cell body in VPL and travel in internal capsule to appropriate region of sensory cortex

Where do the 2 vertebral arteries arise from? Their course?

1st branch of each subclavian artery. Travel medially and superiorly(posteriorly to ICA), entering C6 foramen transversarium up to c1. Pass around superior articular facets of the atlas(c1, that articulate w the occipital condyles) in the groove for the vertebral artery. Pierce dura and arachnoid mater at foramen magnum to enter SUBARACHNOID SPACE

What are the lateral ventricles? Position?

2 large ventricles consisting of anterior horn, body, posterior horn and inferior horn. Deep to the lobes, one in each hemisphere in forebrain

Contents of the anterior fossa of the cranial vault?

2 orbital plates of frontal bone, cribiform plate(above nasal cavity), optic nerves, ICAs, pituitary gland in fossa

What do the 3 spinocerebellar tracts convey? How many neurones form each pathway?

2-neurone pathway. All carry proprioceptive info to cerebellum. Ventral tract= proprio from ipsilateral(DOUBLE CROSSES) , within it runs Cuneocerebellar tract= proprio from ipsilateral upper limb Dorsal tract= proprio from ipsilateral lower limb

Course of the secondary and tertiary neurones in the trigeminothalamic tract from the trigeminal sensory nucleus?

2: following the synpase they decussate across brainstem to form the contralateral trigeminothalamic tract, terminating in VPM in thalamus 3: from synapse in VPM, proceed through internal capsule to cortical territories for face and head sensation

Which CNs innervate muscles derived from the 2nd and 3rd pharyngeal arches?

2nd= VII = muscles of facial expression 3rd= IX = stylopharyngeus

Features of the dorsal brainstem?

3 pairs of cerebellar peduncles, nucleus cuneatus and gracilis(medulla, marked by tubercles in line with the pyramids on anterior surface), diamond depression of 4th ventricle on medulla and pons, superior and inferior colliculi forming midbrain tectum

What is the basis of the Romberg test?

3 sensory inputs for stability: vision, vestibular and proprioception. If lesion in a vestibular or proprioceptice area(i.e. sensory), vision can normally compensate. Romberg test removes vision->instability

How many neurones are in each ascending sensory pathway from the receptor? Where does each one originate and synapse(excluding spinocerebellar?

3. Primary: dendron from receptor to cell body in Dorsal root ganglion(if spinal neurone from trunk and limbs)/trigeminal ganglion(if cranial nerve from head and face). Axon forms synapse with secondary neurone in spinal cord or medulla. Secondary: cell body in cord or medulla, axon decussates and ascends in tract to thalamus. Tertiary: cell body in thalamus, terminates in primary somatosensory cortex

Which CNs innervate muscles derived from 4th and 5th pharyngeal arches?

4th= X = muscles of pharynx and larynx, soft palate 5th= XI = SCM, trapezius

How much CSF is produced a day and how does this differ from the amount present at any one time?

500ml. Only 100-160ml present at a time as most reabsorbed

What is the insula?

5th lobe of brain deep in lateral sulcus. Emotion and self-awareness

How many cerebellar peduncles are there and what is their role?

6, 3 on each half of the posterior brainstem. Connect brainstem to the cerebellum (Superior connects midbrain, Middle connects pons, Inferior connects medulla)

When would bitemporal hemianopia be observed(tunnel vision)?

= loss of temporal half of vision, so lesion at optic chiasm where fibres from nasal half of retina decussate(carry info from temporal field) e.g. pituitary tumour

R Homonymous hemianopia would be indicative of a lesion where in the visual pathway?

=loss of R half of vision in each eye. Lesion of L (contralateral) optic tract (carries fibres from L eye nasal half and R eye temporal half of retina) OR L optic radiation

What is the relevance of the transverse pontine fibres running over the ventral surface of the pons?

=part of intracerebral motor loop. They originate from pontine nuclei, which get supplied by corticopontine fibres from cortex. The transverse fibres run from the nuclei to the contralateral cerebellar hemisphere.

What is athetosis?

A hyperkinetic disorder of the basal ganglia, esp corpus striatum. Choreiform movements, dystonia, slow and writhing, esp distal limbs

What role does the reticular formation play in controlling autonomic and endocrine systems?

ANS: exerts higher control from cortex and hypothalamus on to descending reticulospinal and -bulbar tracts Endocrine: influences hypothalamic nuclei

Where is the abducens nucleus that CN IV fibres emerge from and how does it course?

Abducens nucleus in posterior of caudal pons beneath floor of 4th ventricle. Fibres course ventrally and emerge from ponto-medullary junction. Through laterall walls of cavernous sinus, exiting through SOF

Result of ventricular system obstruction in developing foetus?

Abnormal collection of CSF (often due to aqueductal stenosis). Rapid increase in head size as fontanelles not yet fused. Irreversible brain damage as ventricles continue to dilate

When does the crossed extensor reflex occur?

Activation of flexor withdrawal in one weight-bearing limb simultaneously causes reflex extension of the contralateral limb for stabilisation. (mediated by axon collaterals crossing midline of cord to excite extensor alpha MNs originating in contralateral ventral horn). Axons also ascend to facilitate higher control to shift centre of gravity

Aneurysm differential diagnoses?

Acute bacterial meningitis, severe migraine, tumour, stroke

Types of acute and chronic states of altered consciousness?

Acute= clouding of consciousness, delirium, stupor Chronic= dementia, hypersomnia, vegetative state.

What could cause an acute spinal cord lesion and a chronic one?

Acute= occlusion of anterior spinal artery, trauma causing spinal fracture, Chronic compression= infection, tumour of spine/meninges/nerve root, prolapsed IV disc

How do the paths of the spinothalamic tracts display somatotopic organisation of the dorsal horn/cord grey matter?

Adelta and C nociceptive fibres in lateral tract synapse in Lamina II/substantia gelatinosa (I-III) of dorsal horn. Ventral neurones from mechanoreceptors(crude touch and pressure) synapse in Laminae III-V

What is the pia mater and what does it form?

Adheres to surface of CNS, following the contours of gyri and sulci. Forms 21 denticulate ligaments on each side of cord (attachment to arachnoid and dura to stabilise cord). Also forms the filum terminale

Result of LMN lesion to CNVII? (Bell's palsy idiopathic, or infection or trauma)

All terminal motor branches of facial nerve lesioned->complete paralysis of ipsilateral side of face.

Where does the sphenoparietal sinus run?

Along lesser wings of sphenoid into cavernous sinuses

When might you suspect an intracranial lesion is present?

Altered Glasgow coma scale score(assessment of neurological state) and skull fracture

What is the significance of the Circle of Willis as the blood supply to the brain tissue?

Anastomotic network of the vertebral arteries and ICAs in subarachnoid space , optimising blood flow - theoretically full perfusion of the brain even when one branch occluded/compromised. But still perfusion issues if main branch is occluded

Function of the meninges?

Anchors CNS to bones, protecting from sudden movement. Encloses CSF to act as hydraulic cushion, with brain floating in cranial vault, to dampen sudden movements

What do the 5 groups of vertebral artery branches supply?

Ant spinal=ant2/3 spinal cord Post spinal=post1/3 spinal cord PICA= post inf cerebellum Meningeal branches=bone and dura of posterior cranial fossa Medullary branches=medulla

What do the 3 cerebral arteries supply?

Anterior cerebral= Medial frontal(lower body area of motor and sensory cortex) and parietal lobe, parts of internal capsule and caudate via medial striate branch Middle cerebral= basal ganglia, internal capsule via lateral striate branches, Broca&Wernicke areas and lateral side of each hemisphere(in lateral sensory and motor cortex for face, neck, upper limb) Posterior cerebral= occipital lobe and inferior temporal lobe, thalamus, parts of basal ganglia

What are the 3 divisions based on evolution, and how do they relate to the functional regions of the cerebellum?

Archicerebellum = Vestibulocerebellum (caudal region) Paleocerebellum (adjacent neocerebellum) = spinocerebellum(medial region) Neocerebellum(remainder) = pontocerebellum/cerebro-cerebellum (cerebellar hemispheres)

How can arthritis in the cervical vertebrae cause restriction of blood supply to the brain and spinal cord?

Arthritic projections from the vertebraw(osteophytes) may project and press into the vertebral arteries, and when person twists neck rapidly->occlusion

Which two inputs to ARAS have powerful rousing effects?

Ascending pain pathways, vestibular nuclei(communicates postural status)

Describe the course of the basilar artery. What are its 5 major branches?

Ascends in groove on anterior surface of pons and divides into 2 posterior cerebral arteries at the upper border of the pons. Gives off: -AICA->runs posterolaterally -Labyrinthine artery(sometimes branch off AICA)->laterally through IAM -Pontine arteries->pass laterally -Superior cerebellar->close to basilar termination passes posteriorly, winds round crus cerebri -Posterior cerebral->pass posterolaterally round midbrain

How would Romberg's test be carried out and how can it be used to distinguish between cerebellar and sensory ataxia?

Ask patient to stand unaided with eyes closed, losing balance=positive sign. Sensory ataxia(dorsal column damage)=lose balance only when eyes closed. Cerebellar ataxia(more severe proprio/vestibular lesion or midline lesion)=lose balance when eyes open and closed.

Where do the occulomotor nucleus and Edinger-Westphal nucleus lie in the brainstem?

At the base of the PAG of midbrain at level of superior colliculi. Edinger-Westphal is slightly more dorsal and medial.

Where is the 4th ventricle widest?

At the ponto-medullary junction (arises in rostral medulla from opening out of the spinal cord central canal). Ends at ponto-mesencephalic junction, becoming the cerebral aqueduct.

Why are subdural haematomas common in older patients?

Atrophy of brain tissue, which stretches the bridging veins connecting the dural venous sinuses->rupture esp if on blood thinning meds

What are the posterior attachments of tentorium cerebelli and the dural venous sinuses formed?

Attaches below falx cerebri at internal occipital protuberance, forming confluence of the sinuses. Tentorium then extends laterally to attach at the transverse sulci of the occipital and parietal bones to form the transverse sinuses

What symptoms may be experienced as a result of seizure in temporal lobe and why?

Auditory cortex at superior temporal gyrus->altered hearing Meyer's loop round to occipital lobe->unilateral upper visual field loss Hippocampus and amygdala deep in temporal lobe->memory loss and hallucination, sense of impending doom, aura and old memories resurfacing Wernicke's aphasia

How can multiple sclerosis lead to motor neurone dysfunction?

Autoimmune destruction of myelin, causing both UMN and LMN signs

What ensures we are not too roused?

Axon collaterals received by reticular neurones of ARAS from brainstem nuclei and descending cortical impulses as feedback control. Modulation of activity in ARAS through GATING of afferent fibres

How can an angioma cause problems in the brain?

BV tumour, can compress cranial nerves and brain tissue

Damage in which vessel normally causes Locked-in syndrome? Other potential causes?

Basilar artery(occlusion or haemorrhage)->bilateral ischaemia of VENTRAL pons. Or pontine abscess, brainstem abscess, neck/head trauma, central pontine myelinolysis

What are Baum's loop and Meyer's loop?

Baum's: fibres from superior retina(representing lower visual field) course superiorly to terminate in vusal cortex above calcarine sulcus Meyer's: fibres from lower retina(representing upper visual field) loop into temporal lobe and terminate below calcarine sulcus

How does the cornea account for most of the refraction of light?

Because refractive index for the humour is all very similar so doesn't change much once light has entered eye through cornea. Light refraction is needed to focus an image - allows PERIPHERAL vision

Where is the 3rd ventricle located?

Between L and R thalami, with supraoptic protrusion above optic hciasm and infundibular protrusion above optic stalk

Where is the subdural space? What could cause a subdural haematoma?

Between arachnoid mater and meningeal dura. Normally the 2 are opposed by CSF. Venous blood can collect from cerebral vein damage(as they pierce the dura to empty into the venous sinuses)

Where is the cisterna magna located?

Between cerebellum and dorsal medulla, connected to 4th ventricle by median aperture(foramen of Magendie)

Where is the cerebellopontine cistern?

Between cerebellum and lateral pons, connected to 4th ventricle by 2 lateral apertures(foramina of Luschka)

Where is the epidural/extradural potential space and what structures run in it?

Between periosteal dura and cranium(or vertebral canal of spinal cord). Meningeal arteries, small venous plexuses, lymphatics.

Why would someone who has a subdural haemorrhage show apparent recovery before deteriorating?

Bleeding in subdural space is slow as blood under low pressure, and subdural space is large so blood can spread and the veins will not spasm to stop blood loss. Large bleed needs to occur over time before ICP rises to fatal level->herniation, compression of brainstem and its cardiorespiratory centres->death. Treat by observation if small, or surgical draining

What is brain herniation?

Brain forced through/across falx cerebri, tentorium cerebelli or even foramen magnum. Due to raised ICP, or localised pressure increase in area e.g. due to haematoma. Many classifications

Why is autoregulation of blood flow rate to the brain tissue essential?

Brain has no lymphatic drainage so increase in perfusion due to inc HR/BP will raise ICP. Flow is maintained to brain independently of BP control to rest of body

What signs would be seen in extracranial lesion to CNVII at the stylomastoid foramen and why?

Branches of VII that leave it below the stylomastoid foramen are the 5 terminal motor branches, nerve to digastric and nerve to stylohyoid. Paralysis of ipsilateral muscles of facial expression and scalp around ear

Which column of brainstem motor nuclei are associated with special visceral efferents?

Branchiomotor cell column: Most lateral, from rostral to caudal: -Trigeminal motor nucleus: (rostral pons) Vc->muscles of mastication etc -Facial motor nucleus: (pons) VII->muscles of facial expression -Nucleus ambiguus (lateral midbrain, 3 efferents leave!) most rostral: IX->stylopharyngeus, middle: X->pharynx, soft palate, larynx, caudal: XI->SCM and trapezius

Common site of subdural haematoma?

Bridging veins between superior sagittal sinus and superior cerebral vein running in great longitudinal fissure (blow to back of head)

How are bulbar palsy and pseudobulbar palsy different?

Bulbar means medulla, so refers to CN IX,X,XI& II. Bulbar palsy= LMN lesion of CN 9-12. Dysphagia, difficulty speaking Pseudobulbar= BILATERAL UMN lesion of CN9-12, causing same effects as bulbar + uncontrollable laughing or crying at inappropriate times.

Motor impairments due to lower MN lesions of: C4, C6, T1, L2, S4?

C4: contributes to phrenic=weakened breathing movements and nerve to levator scapulae=weakened elevation of scapula/unopposed depression C6: contributes to musculocutaneous nerve=weakened flexion and supination of arm(biceps brachii), radial nerve=weakened wrist extension(wrist drop) T1: ulnar nerve(flexor carpi ulnaris, flexor digitorum profundus, dorsal interossei)=weakened wrist flexion, finger flexion and finger abduction L2: femoral nerve(anterior compartment of thigh-quadriceps)=weakened flexion at hip&knee extension S4: pudendal nerve=faecal and urinary incontinence

At what level have all tracts joined the spinal cord?

C5

Lesion of which cranial nerve results in the eye adopting a 'down and out' position?

CN III palsy: unopposed lateral rectus and superior oblique so eye displaced inferolaterally

Lesion of which cranial nerve results in eye positioned upwards and inwards? Why may there be accompanying diplopia

CN IV palsy: loss of superior oblique which normally pulls eye down and out. Diplopia due to weakness of downward eye movement

Lesion of which nerve results in adducted eye?

CN VI palsy: loss of lateral rectus which normally pulls eye laterally

Why would atrophy of muscles of facial expression be seen if labyrinthine artery occlusion occurred before the IAM?

CN VII terminal motor branches all affected as they don't arise until after it has entered the IAM. +lacrimal and sublingual&mandibular gland secretion reduced, taste ant2/3 tongue, stapedius innervation

Which tracts would be spared in Locked-In syndrome, with what results?

CNIII(PICA supply and highest nucleus in brainstem, spared). Spinothalamic tract(pain and temp response fine) Cortex(awake and aroused) Lateral reticular formation(breathe on own) Hearing(AICA->labyrinthine artery, and CNVIII fine)

Which CNs may be compromised from space-occupying lesion at: cerebellopontine angle or jugular foramen?

CP angle: CN VII, VIII J foramen: IX, X, XI

What sensory tests would have to be carried out to confirm a positive Romberg sign is actuallty due to sensory issue and not due to another lesion?

Can also get positive sign in UMN/LMN or basal ganglia lesion so test all sensation to cofirm dorsal column damage(convey proprioception, vibration and discriminative touch). Still have pain and temp sensation in cerebellar ataxia as those ascending tracts don't connect with cerebellum

How may untreated syphilis lead to sensory ataxia?

Can lead to neurosyphilis where T. pallidum enters meninges, CSF and cerebral vasculature->inflam and demyelination. e.g. TABES DORSALIS affecting myelination of dorsal columns

Why may coma be associated with accompanying respiratory, pulse, BP and cranial nerve function disturbances?

Cardiovascular and respiratory centres in medulla, and CN nuclei throughout brainstem so often damaged with the ARAS in a lesion

From petrous part of temporal bone, how does ICA get to the medial side of the anterior clinoid process, where it pierces the dura and arachnoid mater?

Cavernous segment: enters cavernous sinus(running adj to CN VI) and curves by 3 90deg turns in the CAROTID SIPHON. Clinoid segment: Where ICA enters cranial cavity proper, extending to medial side of ant clinoid process of sphenoid bone

How is gait seen in cerebellar ataxia different from sensory ataxia?

Cerebellar=lurching, broad-based, difficulty turning and walking in straight line + poss accompanied by nystagmus, dysarthria, pendular deep tendon reflexes. Sensory=high stepping, clumsy uncoordination of movements esp when eyes closed, patient looks at feet when walking.

What drains the 3rd ventricle?

Cerebral aqueduct, into the 4th ventricle

Which cranial nerves arise from the cerebrum? Which arises from the posterior midbrain?

Cerebrum: I(olfactory) & II(optic) Midbrain: IV(trochlear)

How does blood flow to different brain tissues vary, as shown on a functional MRI? Which type of neural tissue requires a greater blood flow rate/supply?

Changes in blood flow to areas according to level of activity. Grey matter requires more, so white matter is supplied by smaller vessels.

Where is the CSF made?

Choroid plexuses within the lateral(most), 3rd and 4th ventricles. These are specialisations of ependymal celsl lining the ventricles, along with loose CT and capillaries.

What muscle is contained within the ciliary body? Role?

Cilary muscle which moves the lens(accommodation reflex)

Where are the descending rubrospinal and lateral corticospinal tracts located?

Close to dorsal horn.

Location of the vestibular nuclei(superior, inferior, medial, lateral)?

Close together in caudal pons and rostral medulla

Define clouding of consiousness, delirium and stupor:

Clouding= reduced wakefulness & awareness, memory loss, lack of attention, drowsy, confused Delirium= high arousal + confusion & hallucination Stupor= abnormal sleep-like state, only rousabed with vigorous stimulation

What is the CSF like in meningitis/bacterial infection?

Cloudy, thick, increased proteins and white cells(neutrophils in bacterial, lymphocytes in viral meningitis), low glucose

What is uncal herniation?

Common type of transtentorial herniation. Uncus(innermost part of temporal lobe) forced across tentorium cerebelli, putting pressure on brainstem(esp midbrain)

What are the ventricles? What are they derived from?

Communiating cavities derived from lumen of neural tube in the brain. Responsible for production, transport and removal of CSF

Signs seen in uncal herniation?

Compression of CNIII-> ptosis(levator palpebrae superioris loss), pupil dilation(sphincter pupillae loss) .Precedes 3rd nerve palsy= motor loss of all extraocular muscles except lateral rectus(VI) and superior oblique(IV)->ipsilateral eye 'down and out' Compression of ipsilateral posterior cerebral artery=ischaemia of ispilateral visual cortex->contralateral visual field defects in each eye(homonymous hemianopia)

How does Horner's syndrome present?

Compression of cervical sympathetic chain->ipsilateral miosis(pupil constricted), ptosis(drooping eyelid), anhydrosis(decreased sweating)

What can cause trigeminal neuralgia and why is the pain so accurately localised?

Compression of part of CN V by BV or tumour. Sudden severe pain episodes affecting one side of face, well-localised due to GSAs.

Outer ear = auricle + external auditory meatus. What is the concha? What innervates the auricle?

Concha=hollow depression in middle of auricle which continues into skull as ext. acoustic meatus. Sensory: Greater auricular nerve, lesser occipital nerve, GSAs from branches of CN VII&X.

What connects and separates the 2 cerebral hemispheres?

Connected by white matter running in corpus callosum - lies inferior to great longitudinal fissue separating the hemispheres.

What is the interthalamic adhesion?

Connection between the 2 thalamus'. Through the 3rd ventricle

What is the innervation of the pupillary constrictor/sphincter and dilator muscles?

Constrictor=circular muscle, parasymp. Pre-gang from Edinger-Westphal(CNIII)->ciliary ganglion Dilator= radial muscle, symp. Post-gang from superior cervical ganglion To adjust amount of light falling on retina

What are the 3 chambers of the eye and what is contained in each?

Containing aqueous humour: Anterior chamber between cornea and iris, posterior chamber between iris and lens. Vitreous humour: vitreous chamber behind lens, to retina.

What is the central canal?

Continuation of the 4th ventricle caudally, to carry CSF into spinal cord

Lesion to the corticospinal pathway?

Contralateral loss of fine motor control of distal flexors for voluntary movement. Rubrospinal compensates for all except the finer control

Result of a lesion to spinal cord at C8?

Contralateral loss of spinothalamic for everything below C8 (as fibres ipsilateral to the lesion wwill have already decussated) and ipsilateral loss of dorsal column for everything below C8 (as fibre on ipsilateral side to lesion have not yet decussated)

Considering the spinothalamic decussates in spinal cord and dorsal column decussates in medulla, what would be the result of a lesion to R internal capsule, or pons?

Contralateral sensation loss for both tracts as the lesion is above where both decussate

Summary of the function of the basal ganglia?

Controls initiation of movement, preventing exaggerated movement. Activates some movements and suppresses/inhibits unwanted movements.

What sensory information does the trigeminothalamic tract convey?

Convey sensory from face head, neck, dura, auditory tube (pain, temp, touch, proprio) through CN V. (Va,b,c carry all sensory modalities except proprioception which is only via Vc, from muscles of mastication)

Where do motor neurones arise and terminate?

Cortex or brainstem to ventral horn or motor nucleus of brainstem(CNs)

What regions in brainstem would be affects by pontine trauma causing Locked-in syndrome?

Corticospinal tract->paraplegia, corticobulbar->paralysis of CN V,VII,XI,XII at their motor nuclei and motor part of CN IX & X in nucleus ambiguus Medial lemniscus->conscious proprioception and fine touch affected Cranial nerve nuclei damage to IV and VI nuclei

How is respiratory pattern used to ascertain level of lesion in brain injury patient?

Corticospinal tract= breathing automatically Forebrain= inc CO2 sensitivity, regular waxing and waning of resp Midbrain= cluster breathing & hyperventilation Pons= apneustic prolonged inspiration Medulla= resp depression - slow, shallow breathing

Which descending pathways are lateral pathways, innervating distal flexors for voluntary movement?

Corticospinal, rubrospinal

Why must 2 samples be taken from a lumbar puncture if blood is present?

Could be from the procedure itself.

Where do the GSE fibres from the occulomotor and GVE(para) from Edinger-Westphal course?

Course together ventrally through midbrain tegmentum medially between the red nuclei and exit medially to the crus cerebri in interpeduncular fossa as root of CN III

Grey matter nuclei contained within the brainstem?

Cranial nerve nuclei, reticular formation, olivary nucleus, nucleus cuneatus, nucleus gracilis, periaqueductal grey etc

What is the role of humour in the eye and what forms the aqueous humour?

Creates intraocular pressure to maintain position of retina and shape of eye. Ciliary epithelium of ciliary body secrete aqueous humour - reabsorbed by ciliary body and drained by canal of Schlemm to venous system

Which CN passes through the cribiform plate of ethmoid bone? Which passess through optic canal in lesser wing of sphenoid bone?

Cribiform= I Optic canal= II

Why is cutaneous pain sensation well-localised, whereas pain from visceral afferents is diffuse?

Cutaneous pain afferents synapse in laminae I&II, visceral synapse in laminae I,V,X

Describe the pupillary light reflex. What nerve fibres form the afferent limb of the reflex? (see diagram)

DIRECT REFLEX: Inc light intensity into one eye->ipsilateral pupil constricts(para) CONSENSUAL REFLEX: pupillary response occurs in contralateral eye too Afferents= some of the fibres from the optic tract->pass to pre-tectal area just above superior colliculus (rest continue to lateral geniculate nucleus of thalamus). Interneurones project to the Edinger-Westphal nucleus on each side, which is why there is a consensual reflex.

Result of a unilateral lesion to the dorsal column medial lemniscus(DCML)? Result of a unilateral lesion to the dorsal column in the spinal cord?

DMCL: Loss of contralateral fine touch and proprioception (as fibres decussated in medulla). Small number of tactile fibres travel in the spinothalamic tracts so can still perform tasks related to tactile info processing Cord level: Ipsilateral sensory loss as fibres have not yet decussated.

Which descending pathways decussate, and which stay ipsilateral?

Decussate: lateral corticospinal, rubrospinal(ventral tegmentum decussation), tectospinal(dorsal tegmental decussation) Ipsilateral: reticulospinal, vestibulospinal

What is the internal capsule?

Dense white matter in unferomedial part of each hemisphere, running between the thalamus and lentiform nucleus in a sort of L. Contains ascending(except spinocerebellar tract) and descending axons to and from cortex. (corticospinal tract constitues a large component)

Why are the ventral horns larger than the dorsal horns in the spinal cord?

Despite there being more sensory neurones, the cell bodies of the LMNs are larger

Location of the cerebellum?

Develops from metencephalon (from rhombencpehalon), in posterior cranial fossa, dorsal to the 4th ventricle and thus the brainstem. Attaches to the brainstem divisions by 3 pairs of cerebellar peduncles.

How does the visual tract and cortex display retinotopic organisation?

Different parts of retina represented discretely through it. e.g. macula represented disproportionately by large vols of lateral geniculate nucleus and visual cortex

Major causes of altered states of consciousness?

Diffuse encephalopathy(generalised disturbance affecting whole brain e.g. metabolic and toxic disturbance), Direct brainstem lesion, Indirect brainstem compression by supratentorial mass lesion(tumour/oedema/haematoma)->herniation

Where is the reticular formation?

Diffuse longitudinal orientation of nuclei, with neurones running through the dorsal part of brainstem up to the midbrain tegmentum. Long dendrites to interact with most fibres running through brainstem

Difference between diffuse and focal brain injury?

Diffuse= patient usually unconscious immediately as grey&white matter accelerate&decelerate at diff rates->shear globally at their interface Focal= patient generally conscious, secondary brain injury from primary trauma can cause oedema/haematoma/swelling and raise total ICP->lose consciousness

What is hypersomnia?

excessive drowsiness and intermittent waking

What is a tract?

grouping of fibres sharing a common course, origin and termination

Causes of unilateral mono-ocular blindness e.g L eye?

Disease of ipsilateral eyeball(e.g.cataract, intraocular haemorrhage) or disease of ipsilateral optic nerve(MS, tumour).

What are Rinne's and Weber's tests useful for?

Distinguishing between conductive(obstruction of mechanical transmission) and sensorineural(dysfunction of inner ear/organ of corti/CN VIII) hearing loss

Summary of function of cerebellum?

Does not initiate movement, but refines it. Comparator of intended movement(motor) and actual(ascending sensory) to correct discrepancies, timing/sequencing motor activation for smooth, appropriate movement and postural adjustment and maintenance(GAIT), predictor enabling rapid execution of movements based on prior experience, instigating learned motor sequences

Which ascending tracts are the most exterior in the spinal cord white matter?

Dorsal and ventral spinocerebellar

Anatomical location of the 4th ventricle?

Dorsal aspect of brainstem, at pontine-medullary junction. Dimond-shaped

What is the tectum of the brainstem?

Dorsal portion of midbrain, forming roof. Consists of superior(visual) and inferior(auditory) colliculi.

Why is weakness and not full paralysis of a muscle not seen in LMN lesions?

Due to presence of plexi - many roots contribute fibres to a single nerve branch (e.g. radial n carries fibres from C5-T1)

Why would there be a contralateral loss of sensation to all the dermatomes below a unilateral lesion of the spinothalamic tract?

Due to their immediate decussation at the level of their synapse in the dorsal horn.

How is an aneurysm treated?

Emergency: reduce ICP and restore respiration Surgical: endovascualr clipping at junction, endovascular coiling (catheter through femoral artery, insertion of platinum coil at junction to promote thrombus formation)

What is the cause of syringomyelia, where a syrinx forms in the spinal cord?

Enlargement of central canal, forming fluid filled cyst, compressing the ventral white commissure. The lateral spinothalamic neurones course here due to their decussation at the ventral white commissure->loss of pain and temperature sensation

How do the clinical signs in central herniation progress?

Erratic respiration and increased limb tone->decorticate rigidity->decrebrate rigidity->death. (slower progression than uncal)

What are the attachments of the falx cerebri and what sinuses does it contain within as a result?

Ethmoid bone anteriorly, posteriorly to internal occipital protuberance and superior surface of tentorium cerebelli, splitting to contain straight sinus. Extends all the way into the great longitudinal fissues, so contains the superior and inferior sagittal sinuses too.

Where is the cavernous sinus and what are the boundaries?

Extends from posterior orbit to petrous part of temporal bone, either side of sella turcica(sphenoid). Roof=dura, floor=greater wing of sphenoid, medial wall=body of sphenoid, lateral wall=meningeal dura

What is Babinski's sign? Is its presence normal?

Extensor plantar reflex - big toe extends in response to stroking plantar surface of foot. Not normal in people>2yrs due to incompleted myelination of corticospinal tract (toe normally flexes). Present in pyramidal tract lesions(corticospinal).

How may bacterial infection be transmitted to the cavernous sinus?

External facial injury to the danger triangle, becomes infected->spread into facial vein which gives off superior opthalmic vein ->connects with the cavernous sinus->transmission of infection

What is the difference between an extradural and subdural haemorrhage?

Extradural= between dura and skull. e.g. middle meningeal artery at pterion Subdural= tearing of venous vessel or dural venous sinues e.g. superior cerebral veins where they drain into superior sagittal sinus

How is pathological nystagmus different from normal nystagmus situations?

Eyes drift away from the visual field and correction with saccades(ballistic eye movments to focus fovea on object). Jerk(slow drifting, fast correction with saccades) or Pendular(slow drifting and correction). Drifting may cause large sight impairment

What are the two tracts forming the dorsal columns and where are they located on horizontal section of spinal cord?

Faciculus gracilis(Medial): lower limbs and trunk Fasciculus cuneatus(Lateral): upper limbs (C6-T1) Convey fine discriminative touch and proprioception (ABeta fibres) Located between dorsal median sulcus and dorsal horn

What are the 4 major reflections of the meningeal dura and what do they partition?

Falx cerebri: 2 cerebral hemispheres. Crescent-shaped in the great longitudinal fissure. Falx cerebelli: cerebellar hemispheres Tentorium cerebelli: occipital lobes from cerebellum Diaphragm sella: pituitary from hypothalamus. Covers the pituitary fossa in the sella turcica(sphenoid bone) with opening for infundibulum and vessels

Which 2 ascending tracts form the dorsal white columns?

Fasciculus gracilis and cuneatus. At dorsal part of spinal cord between the dorsal horn and posterior median sulcus

Causes and symptoms of aneurysms?

Female, age, smoking, hypertension, carotid artery stenosis, Ehlers Danlos(collagen deformity), high cholesterol ->thunderclap headache, stiff neck(inflamed meninges), photophobia, stroke symptoms(unilateral face drooping, speech slurred)

Explain the Parkinsonism gait, seen in Parkinson's disease

Festinant gait(accelerated short steps) due to muscle hypertonicity, reduced arm swinging. Difficulty initiating and terminating movement

What limits the spinal cord movement when the spine is flexed?

Filum terminalis: extension of pia mater fusing with dura, attaching to 1st part of coccyx

Which tests can indicate a hemispheric cerebellar lesion?

Finger-to-nose test, heel-to-knee test (dysmetria), clapping of hand using alternating palmar and dorsal surface of other hand(diadochokinesis), knee jerk reflex will be pendular(lack of cerebellar influence over input from muscle stretch receptors that would normally terminate the movement)

Which reflex is activated upon noxious cutaneous stimulation of a limb?

Flexor withdrawal reflex. Mediated by polysynaptic GTO reflex - afferent->interneurone->alpha MNs to flexors excited, alpha MN to extensors inhibited. (normally this reflex inhibited by descending pathways if the stimulus is not noxious)

How is an uncal herniation exacerbated as it progresses?

Flow of CSF interrupted, futher increasing ICP

Where is the foramen lacerum in relation to the carotid canal?

Foramen lacerum is anteromedial to carotid canal, also in petrous part of temporal bone

Where are the fovea centralis, macula lutea and optic disc? Why is the optic disc called the 'blind spot'?

Fovea= at centre of macula, highest density of cones. Lies along visual axis, so is where an image is centred. Macula= ring of retina around fovea, with high conc of photoreceptors - for maximising visual acuity Optic disc= medial to macula. Where retinal ganglion cell axons converge and leave eye in the optic nerve. Blind spot as no photoreceptors but filled in by brain

What is the most likely cause of an extradural haematoma?

Fracture of pterion (weakest part of skull) where middle meningeal artery runs beneath

What is the tentorial notch formed by? Why is it important clinically?

Free anterior and medial edge of tentorium cerebelli. Around posterior midbrain and pons, and basilar artery passes through. Provides communication between supra- and infra-tentorial compartments but also a reference site of herniation (lobes of cortex into infra-tentorial compartment)

Where does the internal carotid arise? How is it different in the neck to in the skull?

From common carotid bifurcation at C3/4. Branchless in the neck, enters the skull through the carotid canal and gives off 6 major branches in the skull, within the subarachnoid space.

Where do the transverse sinuses drain from?

From the confluence bilaterally->curve down to form sigmoid sinuses(running in groove between temporal and occipital bones)->IJV

How is CN IX involved in the gag reflex?

GSAs from pharynx run in CN IX into trigeminothalamic tract, but also have connections to nucleus ambiguus and hypoglossal nucleus

How do gamma LMNs under control of the descending pathways influence the stretch reflex?

Gamma MNs cause contraction of the intrafusal fibres in the spindle, lowering their threshold to stretch, increasing their sensitivity

What are the three categories of afferents arriving at the sensory CN nuclei and which CNs carry them?

General somatic afferent: cutaneous touch, pain, temp, proprio from head and face(Va,b,c, VII, IX, X) Special somatic afferent: special sensation from external env(sight, balance hearing) (II, VIII) Special visceral afferent: primarily taste (VII, IX, X)

What are the three categories of efferents exiting the motor CN nuclei and which CNs carry them?

General somatic efferent: to skeletal muscle derived from myotomes of embryo somites (III, IV, VI, VII, XII) General visceral efferent: preganglionic autonomic fibres to smooth muscle (III, VII, IX, X) Special visceral efferent: to muscle derived from pharyngeal arches e.g. muscles of mastication, pharynx, larynx, palate, facial expression) (Vc, VII, IX, X, XI)

What is meant by the term 'cortex'?

General terms for parts of brain outside corpus callosum. Majority = neocortex (6 layers). Rest is allocortex(olfactory and hippocampus) and mesocortex(cingulate gyrus, insula)

Which test can distinguish between open and closed angle(iris adheres to cornea) glaucoma?

Gonioscopy: measures angle between cornea and iris. Tonometry measures intraocular pressure, which is increased in both due to reduced draining of aqueous humour

Input relayed to brain influencing the vestibulospinal pathway? What is its role?

Gravitational sensory input from vestibular labyrinth of inner ear via vestibular nerve to vestibular nuclei, and axial muscle stretch receptors. Helps maintain head and neck position.

What is the straight sinus a continuation of?

Great cerebral vein and inferior sagittal sinus

What signs would be seen from intracranial lesion to CNVII at the internal acoustic meatus?

Greater petrosal n branches off CNVII at IAM= Ipsilateral loss of lacrimal gland function Nerve to stapedius branches off below= ipsilateral hyperacusis Chorda tympani branches off below= ipsilateral loss of taste from ant 2/3 tongue and reduced salivation (submandibular and sublingual glands) 5 terminal motor branches= motor loss of muscles of facial expression

Describe the organisation of the cerebellar cortex:

Grey matter covered by folia forming fissues of varying depths

Organisation of grey and white matter in the brain?

Grey matter(neurone cell bodies) forms cerebral cortex on outside, and discrete nuclei within (brainstem, hypothalamus, thalamus etc) White matter = myelinated axons

Other causes of sensory ataxia?

Guillian-Barre, autoimmune(MS), metabolic peripheral neuropathy(e.g. diabetes), spinal cord compression, neoplasm, hereditary(Friedrich's ataxia)

How are ependymal cells adapted for their function?

Have microvilli to absorb CSF an cilia to circulate it

What happens to the optic nerves at the optic chiasm?

Hemidecussation of the fibres in L and R optic nerves - fibres from nasal half of retina(receiving info from temporal visual field) cross over to join the contralateral tract, running with opposite eye's temporal retina fibres. They then run in 2 optic tracts L optic tract now carries info from the contralateral (R) half of the visual field(L temporal retina and R nasal retina) R optic tract now carries info from L 1/2 of visual field (L nasal retina and R temporal retina)

Give 3 other forms of abnormal gait:

Hemiparetic: asymmetry, synergy of extension and circumduction of affected leg at hip and knee, with foot plantar flexed and inverted. Trendelenburg: weakness of hip abductors(lesion of superior gluteal nerve), causing pelvic drop on affected side Antalgic: avoid certain movement to avoid acute pain(trauma, oteoarthritis)

What is coning?

Herniation of cerebellar tonsils through foramen magnum, compressing brainstem. Poss due to tumour in posterior cranial fossa

Functions of the BBB?

Highly selective to protect neurones from bulk flow, toxins and infectious agents, maintain local env for NTs and nutrients, strict control of what enters and leaves brain(maintain ion balance for electrochemical gradients). Only lipophilic molecules like O2, CO2 can diffuse freely into the cerebral extracellular space

Names of the retinal interneurones which modulate transmission between photoreceptors, bipolar and ganglion cells?

Horizontal and amacrine cells

Which foramen does CNXII pass through? Where is it?

Hypoglossal canal, lateral to foramen magnum.

Which CNs purely carry sensory fibres?

I, II, VIII

Through which cranial foramina do parts of the facial nerve pass through?

IAM: the converged sensory and motor roots pass through as one. Greater petrosal to pterygopalatine branches off here Stylomastoid foramen: Everything has branched off except terminal motor branches for facial expression, nerve to stylohyoid and nerve to digastric

Which CNs are contained in the gap between the tentorium cerebelli attachment to the A&P clinoid processes of the sphenoid?

III & IV

Which CN arises from the midbrain-pontine junction?

III(occulomotor)

Which CNs are involved in controlling eye movement and pupillary constriction?

III, IV, VI. (pupillary contriction=III GVE from Edinger-Westphal nucleus->pupillary sphincter)

Which CNs pass through the superior orbital fissure(between greater and lesser wings of sphenoid)?

III, IV, Va(opthalmic), VI

Which extraocular muscles does CNII supply? And IV & VI?

III= all extraocular muscles except lateral rectus and superior oblique (levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique) IV= superior oblique VI= lateral rectus

Which extraocular muscles are supplied by CN IV and VI? Actions and tests?

IV: superior oblique= depression, abduction, medial rotation (look inferiorly and medially) VI: lateral rectus= abduction (look laterally)

Which CNs pass through the jugular foramen? (lateral to hypoglossal canal)

IX, X, XI

Which CNs arise from medulla?

IX-XII (glossopharyngeal, vagus, accessory, hypoglossal) XII=anterior to olive, XI,X,XI=posterior to olive

Why should a pre-lumbar CT always be carried out?

If patient has raised ICP, lumbar puncture could cause coning as removing CSF in cord creates negative pressure

What is hydrocephalus? Treatment?

Impairment of CSF flow. Treat with shunt draining CSF into R atrium of peritoneum

Where is the facial motor nucleus in the brainstem? Course of the special visceral efferents from here?

In caudal pontine tegmentum(below floor of 4th ventricle), fibres go dorsally to, and loop over, abducens nucleus and leave in motor root->muscles of facial expression. Corticobulbar tract UMNs feed into facial motor nucleus to give control over muscles of facial expression(bilateral for temporal branch, full decussation for lower branches)

Where is the the inferior sagittal sinus and what does it continue as?

In free margin of falx cerebri. Continues as straight sinus->confluence

Where is the superior sagittal sinus formed?

In the fixed margin of falx cerebri

Where are the cardiovascular and respiratory centres of the brainstem?

In the reticular formation in the medulla oblongata, connect with hypothalamus and other nuclei assoc with ANS outflow

What is spasticity and why is is seen in UMN lesions?

Increase resistance to passive movement, detected on quick movements. LMN firing withouth control from higher brain regions. Most visible in attempted upper limb EXTENSION and attempted lower limb FLEXION

What are hemiparesis and paraparesis and what are they main clinical features of?

Indicate UMN lesion. Hemi=unilateral muscle weakness, indicating unilateral UMN lesion Para= partial paralysis of lower limbs due to spinal cord lesion of UMN below T2

Summarise the inputs to the cerebellum:

Inferior olivary nucleus(medulla), vestibular nuclei, reticular formation, pontine nuclei(main excitatory loop), spinocerebellar tracts(spinal cord)

Why is meningitis fatal? Common causes?

Inflammation of meninges induces immune response cuasing cerebral oedema, raising ICP. Can cause herniation compressing brainstem centres and reduced cerebral perfusion. Bacteria(neisseria meningitidis, strep pneumoniae)

What part of the ear is in the petrous part of the temporal bone?

Inner ear, housing vestibulocochlear organs. Vestibular(for balance)= vestibule and 3 semicircular canals Cochlear(for hearing)= cochlea formed of 3 interlinked ducts

Layers forming the retina?

Inner limiting membrane(basement membrane), Nerve fibre layer(ganglion cell axons), Ganglion cell layer(cell bodies of g cells), Inner plexiform layer(synapse between bipolar cells&ganglion dendrites, and amacrine&ganglion dendrites), Inner nuclear layer(amacrine, horizontal and bipolar cell bodies), Outer plexiform layer(rod and cone projections synapsing with bipolar cells), Outer nuclear layer(rod and cone cell bodies) Outer limiting membrane Photoreceptor layer(rod and cone cells) Pigmented epithelium Choroid

Where does the corticobulbar tract arise? Where does it receive input from?

Input from: M1, premotor cortex, supplementary area, somatosensory area. UMN from lateral M1.

Course of the tectospinal tract?

Input= info from CNII(retina) and visual cortex(occipital lobe). UMNs from superior colliculus in midbrain, pass anteriomedially around the PAG and cross midbrain in dorsal tegmentum decussation, descent through dorsal pons, medulla and cord medially, synapse predominantly in cervical segments to orientate movements of head and eyes in relation to visual and auditory stimuli

Major inputs and outputs for the basal ganglia?

Input=cortex->striatum. Output=SNr/GPi->thalamus->cortex(feedback)

Summarise the main inputs and outputs for the reticular formation:

Inputs: spinothalamic tract, medial lemniscus(dorsal columns), CN nuclei, cerebellum, subthalamic, hypothalamic, thalamic nuclei, cortex Outputs to: cerebellum, reticulospinal tracts, parasymp outflow, cerebellum, red nucleus, substantia nigra, colliculi, cortex, nuclei of diencephalon

Major inputs and outputs for cerebellum?

Inputs= ascending spinocerebellar tracts, cortex, vestibular nuclei, climbing fibres from inferior olivary nucleus, mossy fibres from brainstem nuclei(like red, reticular). Outputs= red nucleus, reticular formation and via deep cerebellar nuclei to cortex (main excitatory loop)

Why is the internal capsule commonly the site of a (lacunar) ishaemic stroke?

Internal capsule, caudate nucleus and lentiform nuclei supplied by lenticulostriate arteries branching from the middle cerebral artery. These are very narrow 'end arteries' with no collateral supply so cause stereotyped stroke syndromes.

Where do all the dural venous sinuses drain?

Internal jugular vein

What 3 types of afferent info are conducted by the ascending tracts?

Interoceptive: interoreceptors in viscera sense internal environment(e.g. chemoreceptors) Exteroceptive: superficial mainly in skin, responding to nociceptive stimuli, touch, temp, pressure (e.g. Meissner's corpuscle) Proprioceptive: For awareness of position and movement in 3-D space, from Golgi tendon organs and muscle spindles. Primary afferents synapse in lamina VI(only in cervical and lumbar regions)

Differential of abnormal gait?

Intoxication (Romberg's test done in drunk driving tests)

What is nystagmus and is it ever normal?

Involuntary repetitive to-and-fro oscillations of the eyes. Physiological nystagmus in head movements(vestibular) or eye movement following fast scenes(opticokinetic) to keep fovea on visual field.

Cerebellar symptoms of PICA occlusion (via inferior cerebella peduncle)?

Ipsilateral hemi-ataxia, dysmetria (reduced unconscious control of motor tone, equilibrium, coordination and motor learning)

How would a unilateral cerebellar lesion present?

Ipsilateral incoordination of arm and leg, ipsilateral intention tremor causing unteady gait

Lesion to the spinocerebellar tract?

Ipsilateral loss of muscle coordination, but not normally damaged in isolation.

What are the iris and pupil?

Iris = anterior muscular ring of smooth muscle extending into lumen of eyeball. Pupil = central aperture of the iris, through whit light enters from through cornea to retina.

What is Brown-Sequard syndrome?

hemisection of spinal cord, affecting dorsal columns that have not yet decussated (ipsilateral fine touch and proprioception), spinothalamic(contralateral loss of pain, temp, crude touch)

Which vessel would be implicated in a stroke patient with loss of sensation and motor function of the R arm and hand?

L middle cerebral artery: supply includes lateral frontal and parietal lobes, which includes lateral primary sensory and motor cortices (arm) - via its superficial branches.

Which artery supplies the inner ear and which foramen does it pass through?

Labyrinthine artery (branch of basilar artery). Accompanies CN VII&VIII through internal acoustic meatus

How can a complete occlusion of the labyrinthine artery lead to a sudden fall, vertigo, nausea and hearing problems?

Labyrinthine artery supplies inner ear vestibulocochlear apparatus: vestibular nerve=loss of balance->fall to ipsilateral side. cochlear->ipsilateral hearing loss, tinnitus.

How does the grey matter (dorsal an ventral horns) also have somatotopic organisation?

Laminations: 10, numbered from dorsal to ventral. In ventral horn: Cell bodies of LMNs to proximal muscles medial(ventromedial descending pathways), distal muscles lateral(lateral descending pathways). Flexors(lateral pathways) posterior to extensors(ventromedial pathways).

Which descending tract lies bordering the posterior part of the ventral horn?

Lateral corticospinal

Locations of the 2 spinothalamic ascending tracts in a horizontal section of the spinal cord? What sensory modalities does it convey to the cortex?

Lateral spinothalamic: carries pain and temperature info. (Adelta and C fibres) Lateral to ventral horn Ventral spinothalamic: carries non-discriminative touch and pressure. Ventral to ventral horn

Where is the foramen spinosum? What structures does it convey?

Lateral to foramen ovale. Middle meningeal artery and vein, meningeal branch of mandibular nerve.

Where is the ascending lateral spinothalamic tract? And the ventral spinothalamic tract?

Lateral: ant to rubrospinal(descending) Ventral: just lateral to anterior median sulcus of spinal cord

Why are people advised not to drive in immediate period following a stroke?

Leg weakness and the pedals, drowsy and vision issues, cognitive effects. + stroke can cause EPILEPSY (not generalised seizure as symptoms unilateral)

What is the name of the central aperture of the ciliary body(ring-shaped tissue thickening containing ciliary muscle)?

Lens= transparent, biconvex. Focuses light onto retina. Attached to ciliary body via suspensory ligaments.

Explain the abnormal posture seen in decorticate rigidity:

Lesion above red nucleus(hemispheres, internal capsule, thalmus) Upper limb flexion: facilitation of rubrospinal tract due to disinhibition of red nucleus outweighing retoculospinal and vestibulospinal tract extension. Extension of spine and legs with feet turned inward: disruption of corticospinal tract= biased towardsreticulospinal and vestibulospinal-mediated extension GCS motor=3

When would you see L homonymous hemianopia with macula sparing? Why is the macula spared?

Lesion at contralateral occipital cortex. Macula spared as macula tract has dual blood supply (posterior ceebral artery + branch of middle cerebral artery)

Explain the abormal posturing seen in decererate rigidity:

Lesion in brainstem below red nucleus Extension and internal rotation of arms and legs: disruption of rubrospinal and corticospinal, so extension-biased GCS motor=2

Homonymous quadrantopia of R Upper quadrant of both eyes' vision be due to?

Lesion of L Meyer's loop, as representation of the visual field on the visual cortex is laterally and vertically inverted. Meyer's loop feeds in below calcarine sulcus, so carries fibres representing upper half of vision of contralateral side.

Homonymous quadrantopia of L Lower quadrant of each eye?

Lesion of R Baum's loop( Baum feeds into visual cortex above calcarine sulcus so represents lower half of visual field of contralateral side)

What may cause a bilateral cerebellar lesion and how would this present?

Lesion of vermis, MS, tumour/bleed causing raised ICP and herniation. ->bilateral disarthria, staccato speech, ataxia

Where does the brainstem lie? What forms it?

Lies on basal portion of occipital bone(clivus), attached dorsally to the cerebellum by the cerebellar peduncles. Midbrain+pons+medulla->continuous with spinal cord at the foramen magnum

What is an aneurysm and how do they cause symptoms?

Localised dilation of arterial wall, at risk of rupture due to weakened collagen in tunica adventitia(congenital or due to disease or arterial wall). Symptoms by spontaneous rupture or direct pressure on surrounding structures

Difference between Locked-in syndrome and persistent vegetative state(PVS)?

Locked-in: State of wakefulness and awareness(tegmentum of pons spared) but cannot move/quadriplegia aphonia and paralysis of lower CNs due to massive brainstem infarction(rostral midbrain spared so can communicate by eye movement(CNIII). Functioning cortex. PVS: Result of head injury causing extensive cortical damage. Lack of awareness/conscious intelligence. Sufficient sparing of brainstem and diencephalon so patient can breathe spontaneously and maintain sleep-wake cycles

What is the cause of hypotonia and fasciculations seen in LMN lesion?

Loss of alpha mn innervation to extrafusal fibres=loss of normal resting muscle tone. Release of NT from damaged neurone at the NMJ=twitching

What would be the outcome of damage to T10 nerve root?

Loss/altered sensation around level of umbilicus

What would the consequences be of dislocation of T10&11 vertebrae?

Lumbar cord damage. Bilateral or unilateral. Weak sensation and movement in lower limbs, loss of voluntary bowel and bladder control. Retain use of arms so can self-care, use wheelchair.

Where do the lumbar and sacral cords sit in the vertebral column?

Lumber T9-11, sacral T12-L1(where it forms conus medullaris)

Describe the features of the 3 auditory ossicles:

Malleus- largest, most lateral. Attaches to tympanic membrane via handle of malleus Incus- body&2 limbs. Body articulates with malleus. Short limb articulates with middle ear posterior wall, long limb with stapes Stapes- smallest bone, stirrup shaped. Foot-shaped part attaches into oval window

Which descending motor tracts lie next to the anterior median sulcus in the spinal cord?

Medial longitudinal fasciculus(tecto and vestibulospinal), ventral corticospinal, medial/pontine reticulospinal

Where do the vagus nerve rootlets attach on the brainstem? Where is the dorsal motor nucleus of the vagus n?

Medulla, caudal to the glossopharyngeal rootlets. Dorsal motor nucleus is in medulla, below floow of 4th ventricle (GVEs)

Where is the trigeminal motor nucleus located?

in pontine tegmentum, medial to trigeminal chief sensory nucleus. Efferents leave in motor root and join Vc division of CN V

What signs would be seen as a result of a stroke in the L internal capsule?

Mental impairments(e.g. aphasia), R contralateral spastic hemiparesis and Babinksi sign(UMN lesion), R contralateral hemisensory loss

What embryological structure forms the midbrain?

Mesencephalon

What makes up the hindbrain and what is the embryological origin?

Metencephalon=pons, cerebellum Myelencephalon=medulla

Blood supply and innervation to the meninges?

Middle meningeal artery and vein, trigeminal nerve(meningeal branch of mandibular nerve)

Which layer is the vascular layer of the eye? Where does it lie? Importance of the dark pigment it contains?

Middle uveal tract, lining the sclera. Mostly formed of choroid(darkly pigmented) which absorbs light - reduces reflection within the eye. Anteriorly becomes ciliary body and stroma of eye

How may a midline lesion and a hemispheric lesion of the cerebellum present differently?

Midline: characterised by imbalance, trunkal ataxia(can't sit or stand without toppling), bobbing head movements, may be nystagmus, ocular dysmetria(over or undershooting). Hemispheric: characterised by limb uncoordination. Dsdiadochokinesis(irregular performance of rapid altering movements), intention tremor(tremor when trying to perform an action e.g. buttoning shirt), dysmetria

Why are the cervical and lumbar spinal segments larger?

More grey matter (esp ventral horn) due to motor output to limbs. Cervical the largest (most white matter)as greatest number of tracts leaving/entering cord

General rule motor loss seen from unilateral lesion of corticobulbar tract?

Most CNs have bilateral innervation as some of the UMN fibres decussate prior to synpase at the brainstem motor nuclei. So unilateral UMN lesion would cause mild muscle weakness. Exceptions are CNXII(hypoglossal) and all motor branches of CNVII except temporal, which have contralateral innervation only(unilateral)

What are the cerebral peduncles?

Most anteriro part of the midbrain, all of the midbrain except the tectum. (crus cerebri most anteriorly, pretectum and tegmentum). Contains large descending(in crus cerebri) and ascending tracts connecting brainstem to thalamus(to cortex)

Where do saccular aneurysms commonly occur in the brain and what can rupture cause?

Most common form, outpouching of tunica intima and media due to damaged elastic lamina. Typically at junctions in circle of Willis: between Ant cerebral and communicating artery, Post communicating where it branches off ICA, middle cerebral at a trifurcation or bifurcation ->subarachnoid haemorrhage

Why is the middle cerebral artery known as the 'artery of stroke'?

Most common site of ischaemic stroke, due to direct path of blood flow from ICA, carrying emboli

Location of the spinocerebellar tracts on horizontal section through the spinal cord?

Most lateral, right at the edge of the cord white matter

How is glue ear medically managed?

Most resolve spontaneously. If persistent=severe hearing loss, developmental difficulties with speech, education and socially. Grommet inserted surgically to drain fluid from middle ear

Anatomical location of the primary sensory and motor cortices? What are they separated by?

Motor=pre-central gyrus in frontal lobe Sensory=post-central gyrus in parietal lobe, receiving input from VPL and VPM of the thalamus Separated by central sulcus

What is Charcot's triad a characteristic of?

Multiple sclerosis: nystagmus, dysarthria, intention tremor

Why is muscle atrophy not seen in Parkinson's but overall drop in muscle power is?

Muscle power= speedxstrength No denervation so no atrophy and no incr muscle weakness, but speed reduction

What is the difference between myopia and hypermetropia?

Myopia= short-sighted. Longer eye ball so light focused in front of retina. Corrected by concVEX lens to focus the light less. Hypermetropia= long-sighted. Shorter eyeball so light focused behind retina. Correct with conCAVE lens to focus light more

Signs seen in coning?

Neck rigidity, compression of glossopharyngeal(IX), vagus(X), hypoglossal(XII)

Results of reduced/disturbed arterial supply to area of the brain?

Neuronal death. As they are terminally differentiated, they cannot repair

Is the BBB complete?

No - incomplete around pituitary and pineal glands to allow hormones into circulation, and around chemoreceptor trigger zone in medulla(senses systemic toxins and induces nausea and vomiting), parts of hypothalamus monitoring plasma components, choroid plexuses

Is blood expected in the CSF in subdural haematoma? Would a lumbar puncture be carried out to determine this?

No, as CSF runs in the subarachnoid space (unless arachnoid mater was also torn in the trauma). Expected in haemorrhage of branch of Circle of Willis. No lumbar puncture as this carries risk of coning due to raised ICP

Is there any blood supply and innervation to the arachnoid mater?

No.

What is the conjunctiva and how can it become inflamed?

Non-keratinised stratified squamous epithelium lining inner eyelid and covering sclera. Inflamed by infection/allergic reaction/irritant. Red, itchy, watering, sticky eye

What are the 2 types of hydrocephalus?

Non-obstructive: functional impairment of arachnoid granulations e.g. fibrosis of subarachnoid space following haemorrhage. Obstructive: blockage of ventricular system, commonly cerebral aqueduct. Can be due to subdural haemorrhage

Why is the visual field non-uniform? How does it show lateral and vertical inversion onto the visual cortex?

Nose obstructs nasal vision and brow ridge obstructs superior vision. Visual field= 4 quadrants, each quadrant projects to the opposite quadrant of visual cortex e.g. RUQ will project to LLQ of visual cortex in Meyer's loop (on L, below calcarine sulcus)

PICA occlusion leads to Lateral medullary syndrome(PICA syndrome). Which CN nuclei are affected?

Nucleus ambiguus laterally up dorsal medulla->X and IX efferents(dysphagia, dysarthria, hoarseness, diminished gag) Spinal part of trigeminal sensory nucleus laterally up dorsal medulla->CN V,VII, IX, X(ipsilateral loss of pain and temp sensation from face, teeth, etc) Vestibular nuclei->effect on vestibulosopinal tract(nystagmus, nausea, vertigo, impaired vestibulo-ocular reflex)

Role of the periaqueductal grey (PAG)?

Nucleus in centre of dorsal midbrain, surrounding cerebral aqueduct. Site of integrated autonomic, behavioral, and antinociceptive stress responses

Where is the hypoglossal nucleus? Route of CN XII from here to intrinsic and extrinsic muscles of tongue?

Nucleus in dorsal rostral medulla at level of olives. Axons course ventrally through medulla, emerging as line of rootlets along ventrolateral medulla between pyramid and olive

Which sensory nucleus is associated with special visceral afferents?

Nucleus solitarius. VII(taste anterior 2/3 tongue), IX(taste post 1/3 tongue), X(taste epiglottis and root of tongue)

What are the contents of the cavernous sinuses(laterally on either side of sella turcica of ethmoid)?

OTOMCAT: Oculomotor(III), trochlear(IV), opthalmic(Va), maxillary(Vb) down lateral edge internal Carotid artery and abducens(VI) lateral to pituitary gland.

Which sinus runs through the falx cerebelli?

Occipital sinus, from edge of foramen magnum towards confluence(at internal occipital protuberance)

Where are the petrosal sinuses and what do they drain?

On ridge of petrous part of temporal bone. Drain cavernous sinus into IJV

A common cause of mortality in aneurysm?

Other than the raised ICP effects, vasospasm of the ruptured artery occurs, causing infarction. Prevent with Calcium antagonists

What is 'glue ear' known as medically?

Otitis media with effusion: fluid collection in middle ear. Common in children due to shorter eustachian tube. ->hearing impariment, intermittent pain, poss balance problems.

The 3 histological layers of the cerebellar cortex?

Outer molecular layer(parallel excitatory granule cell axons, stellate and basket cell bodies, inhibitory Purkinje cell dendrites) Purkinje cell layer Inner granular layer(granule cell bodies, Golgi inhibitory interneurones)

What are the 2 layers of the dura?

Outer periosteal(adheres to skull to form periosteum), inner meningeal(forms reflections containing the dural venous sinuses)

The innermost eye layer is the retina. What is this an outgrowth of and what is the non-neural part of it?

Outgrowth of CNS, retinal pigmented epithelium is non-neural and is in contact with the choroid of the vascular layer. Neural part of retina lies under, as the innermost layer

How is the rostral midbrain spared in Locked-in?

PICA supplies brainstem to the level of the superior colliculi(occulomotor nucleus)

Which parts of the brain does the posterior inferior cerebellar artery supply?

PICA=branch of vertebral artery, coursing round medulla over inferior cerebellar peduncle, dividing into 2 branches at the underside of cerebellum. Supplies lateral medulla, PI cerebellum

Blood supply and drainage of the cerebellum?

Paired superior cerebellar(basilar), AICA(basilar), PICA(vertebral) arterial supply. Venous drainage by superior and inferior cerebellar veins->superior petrosal, transverse and straight dural sinuses

Which column of brainstem motor nuclei are associated with general visceral efferents?

Parasympathetic cell column. From rostral to caudal: -Edinger-Westphal most rostral(midbrain, medial to superior colliculus and above oculomotor GSE nucleus) III->ciliary ganglion->sphincter pupillae and ciliary muscles for light and accommodation reflexes -Superior salivatory(medial in pons) VII->submandibular ganglion->submandibular&sublingual glands, or ->pterygopalatine ganglion->lacrimal gland) -Inferior salivatory IX->otic ganglion->parotid gland -Dorsal motor nucleus of vagus->many ganglia->tracheal and bronchial smooth muscle, GI smooth muscle, heart rhythm

What is the ascending reticular activating system?

Part of reticular formation extending from caudal medulla to rostral midbrain (so need intact brainstem). Main part is central tegmental tract receiving ascending afferent input from spinal cord, CN nuclei. Modifies and sends output to thalamus, cortex, hypothalamus, through polysynaptic pathways to bring about roused state(conscious processing in cortex)

What is a tasorrhaphy and when is it indicated?

Partially stitching eye together to keep it moist (when innervation lost to lacrimal gland)

Outline the 2nd and 3rd segments of the ICA's course

Petrous part: ICA enters skull through carotid canal in petrous part of temporal bone and runs anteromedially Lacerum segment: ICA traverses the foramen lacerum(passes through superior part of foramen as inf is occluded by fibrous tissue).

How does Weber's test distinguish between unilateral conductive and sensorineural hearing loss?

Place vibrating tuning fork in centre of forehead to compare conduction in both ears. Normal= equally loud in both ears Conductive loss= louder in affected side(as vibrations go directly to inner ear, and ambient background noise not attenuated) Sensorineural loss= louder in unaffected side

Which CNs arise from the pons and pontine-medullary junction?

Pons= V(trigeminal) Junction= VI(abducens), VII(facial) VIII(vestibulocochlear)

Where do the descending reticulospinal tracts lie in cord?

Pontine(medial) reticulospinal lies medial to ventral horn near anterior median sulcus, Medullary(lateral) reticulospinal lateral to dorsal horn

How do the descending outputs from the pontine and medullary reticulospinal tracts have opposing effects?

Pontine= increase muscle tone to leg extensors to maintain standing posture, enhances anti-gravity reflexes of spinal cord Medullary= frees anti-gravity muscles from reflex control, allows voluntary override of reflex

What are the final 4 branches of the ICA?

Posterior communicating artery and anterior choroidal artery(given off in communicating segment). ICA ends as bifurcation into anterior and middle cerebral arteries

What branch of the ICA forms the posterior linkage in the circle of Willis?

Posterior communicating= extends posteriorly to anastomose with ipsilateral posterior cerebral artery(terminal branch of basilar)

What are arachnoid granulations?

Projections of arachnoid mater into the subdural space, allowing CSF to enter circulation(function as one-way valves - CSF flows along pressure gradient from subarachnoid space)

3 main functions of CSF?

Protection: hydraulic cushion Buoyancy: suspending brain reduces weight, preventing excess pressure on base of brain Chemical stability: maintains microenvironment for neurones to function e.g. keeping K+ low extracellularly

What other assessments may need to be performed alongside the GCS to determine level of a lesion?

Pupillary light reflex(CN3 highest brainstem CN nuclei), Basic reflex eye movements(show brainstem damage or cortical damage removing control of nuclei for III,IV,VI), Motor response to pain(contralateral side to lesion is affected) - may see decorticate or decerebrate response Respiratory pattern

Which descending pathways are pyramidal? (i.e. run through medullary pyramids) Which are extra-pyramidal?

Pyramidal= corticospinal, corticobulbar Extra-= vestibulo-, tecto-, reticulo-, rubrospinal

Features of the ventral brainstem?

Pyramids running medially up medulla surface lateral to ventral median sulcus, olives lateral to tops of pyramids(containing inferior olivary nucleus connecting to vestibulo-cerebellum), transverse pontine fibres, cerebral peduncles (crura cerebri), mamillary bodies between the crura

Where would a stroke-causing lesion have occurred if weakness in the L lower limb was seen? What explains later development of upper limb symptoms?

R medial pre-central gyrus. Cortical damage spread laterally over the pre-central gyrus

How are connections to the hypoglossal nucleus important in chewing&swallowing, and in talking?

Receives afferents from trigeminal sensory nucleus for reflex control of chewing, swallowing. Receives corticobulbar tract UMNs for controlling voluntary tongue movements for speech articulation

Outline the auditory pathway of the cochlear nerve:

Receptors in Organ of Corti(hair cells)-> primary neurone via IAM to cerebello-pontine angle, bifurcates to synapse with secondary neurones at dorsal and ventral cochlear nuclei(around inf cerebellar peduncle). ->2 to superior olivary nucleus in pons(gives off some fibres) and ascends to inferior colliculus and synapses ->3 as lateral lemniscus to medial geniculate nucleus of thalamus, synapse ->4 to superior temporal gyrus(auditory cortex)

What is an epidural?

Regional anaesthesia injected into epidural space in cord (between dura and spinal canal) - in labour to block sensory neurones

Describe the course of the nerve fibres from the retina to optic chiasm

Rods and cones->bipolar cells->ganglion cell axons converge at optic disc to form L or R optic nerve (each contains fibres from both the nasal and temporal part of retina).

Which CNs pass through the foramen rotundum and foramen ovale in greater wing of sphenoid?

Rotundum= Vb(maxillary) Ovale(more lateral and posterior)= Vc(mandibular)

How do the vertebral arteries terminate?

Run alongside medulla and converge to form basilar artery at pontine-medullary junction (so large part of the medulla is supplied by the vertebral arteries rather than basilar)

Some primary fibres of the lateral spinothalamic tract do not synapse then decussate within one segment of entering the spinal cord. Where do they course instead?

Run in dorsolateral tract of Lissauer which caps the tip of dorsal horn. These are non-myelinated/thinly myelinated axons carrying pain and temperature info and ascend/descend several segments of the cord before synapsing with secondary neurone. Then it decussates and joins spinothalamic tract.

Which course does CN III take from exiting brainstem to leaving the cranial fossa?

Runs anteriorly between posterior cerebral and superior cerebellar arteries->lateral walls of cavernous sinus->through superior orbital fissure. Pre-ganglionic para fibres synpase in ciliary ganglion->ciliary nerves to constrictor pupillae and ciliary muscle

What is a complex partial focal seizure and how may tingling and seizure spread over the body from one location?

Seizure arising in one hemisphere, leading to altered consciousness(simple=no loss of consciousness). 'Jacksonian march' of synchronous electrical activity over motor cortex, manifesting as unilateral spread of tingkling and twitching over body mapped by motor homunculus

Why are the dorsal columns more prominent in the cervical segments?

Sensory to head and neck

Testing of the sensory and motor roots of CN V?

Sensory: touch parts of face with cotton wool and blunt pin. Motor: opening jaw against resistance, clench jaw(feel for masseter and temporalis)

What separates the anterior horns of the lateral ventricles? Where does CSF drain from the lateral ventricles?

Separated by septum pellucidum. CSF drains into 3rd ventricle through interventricular foramen (foramen of Monro)

The trigeminothalamic primary afferents synapse in the trigeminothalamic sensory nucleus of the brainstem. What are the names of the 3 subnuclei?

Sgregated according to sensory modality: Mesencephalic nucleus= most superior, containing prioprioceptive cell bodies. Principal/chief/Primary nucleus= middle part, in pontine tegmentum. Where touch and pressure neurones synapse Nucleus of the spinal tract= inferior part, where pain and temperature neurones synapse

Describe the vestibulo-ocular reflex:

Sharply turning head to one side preserves the image on the centre of visual field because eyes turn in the opposite direction to head movement. Sensory input from semicricular canals->vestibular nuclei. Fibres project to the ipsilateral abducens nucleus and synpase ->some fibres from abducens nucleus directly to ipsilateral lateral rectus and some project in medial longitudinal fasciculus to contralateral oculomotor nucleus for contraction of contralateral medial rectus. Some mossy fibres from vestibular nuclei project to cerebellum(prevents overshoot, finer control of eye movement)

Outline the role of the reticular formation in control of skeletal muscle and control of sensation(somatic and visceral):

Skeletal: modulates muscle tone, modulates reflexes via reticulospinal and -bulbar tracts (reciprocal inhibition), maintaining tone of anti-gravity muscles Sensation: influences all ascending pathways that pass supraspinally

Shape of lens at rest? How does this change in the accommodation reflex?

Slightly flattened and focused on distant objects. To focus on close objects, ciliary muscle contracts to make lens more convex

Which column of brainstem motor nuclei are associated with general somatic efferents?

Somatic cell column: In line with and partly medial to parasymp column. From rostral to caudal: -Occulomotor nucleus:(immediately inf to Edinger-Westphal) III->all extraocular except lat rectus and sup oblique -Trochlear nucleus: (medial to inf colliculus) -Abducens nucleus: (V in pons superomedially to salivatory nuclei) VI(lat rectus) -Hypoglossal nucleus: (medial line up medulla to caudal pons) XII->tongue except palatoglossus (+vagus->palatoglossus)

Summarise the somatic, autonomic and psychological signs seen in Parkinson's(hypokinetic disorder):

Somatic: pill-rolling tremor, festinant gait, dysarthri, hypomimia Autonomic: incontinence, dysphagia, constipation Psych: depression, Lewy body dementia, disturbed sleep(night terrors from L-dopa meds), anxiety

How is the cochlea represented bilaterally above the level of the the cochlear nuclei? What is therefore the result of a unilateral lesion to the auditory pathway above the cochlear nuclei?

Some ascending sencondary neurones in the auditory pathway decussate as the trapezoid body at level of superior olivary nucleus in pons and some stay ipsilateral. Unilateral lesion = no mono-aural deafness - instead loss of auditory acuity and inability to localise the directional origin of sounds

Result of damage to UMN of CNXII?

Spastic paralysis of contralateral tongue(tongue deviates AWAY from side of lesion) except palatoglossus(CNX) due to the UMN full decussation and thus unilateral innervation

Outline the difference between spasticity seen in UMN lesions and rigidity seen in Parkinson's and other extrapyramidal disorders:

Spasticity= resistance to initiation of rapid passive movements, which gives way over remainder of movement->jerk (clasp-knife) Rigidity= resistance persist throughout whole movement as incr muscle tone around whole joint

What is the input into the spino-cerebellum?

Spinal cord ascending spinocerebellar tracts carrying unconscious proprioceptive info from ispilateral side to the proprioceptor

Where do the spinal root and cranial roots of the accessory nerve arise?

Spinal: cell body in ventral horn of cervical cord, ascends into skull through jugular foramen to join with cranial root Cranial root arises from nucleus ambiguus in medulla and joins to spinal root. Both run together as accessory nerve, along with CN X, through jugular foramen to SCM and trapezius (vagus GVEs to muscles of pharynx and larynx)

Where does the red nucleus receive input from?

Spinocerebellum and motor cortex

Where is the cell body of the primary neurone in the auditory pathway?

Spiral ganglion of the cochlea. (organ of corti is the sensory organ which transduces the pressure waves, primary neurone continues from it).

What is consciousness? What is required to be conscious?

State of complete arousal and awareness of seld and external environment. Requires ARAS and functioning cerebral cortex

What forms the striatum, corpus striatum, basal ganglia?

Striatum= caudate + putamen Corpus striatum= striatum + globus pallidus Basal ganglia= striatum + globus pallidus + substantia nigra + subthalmic nucleus

Name given to a unilateral vascular insult to an area of brain (esp white matter) by either infarction or haemorrhage cutting off blood supply?

Stroke (ischaemic- blocked small BV supplying white matter, or haemorrhagic)

Where is a lumbr puncture taken from and why?

Subarachnoid space below L3 vertebra - to obtain CSF but avoid spinal cord(conus medullaris forms at L1). Cauda aquina nerve can move out of the way of needles.

What is a reflex? Outline the basic reflex pathway.

Subconscious, involuntary, stereotyped response pattern to a certain stimulus. Act as basic defence mechanisms. Quantitive nature(duration, extent) may vary due to intersegmental and supraspinal influences Stimulus->afferent->CNS->efferent->effector

What are the actions of the extraocular muscles innervated by CN III? (In which direction should patient be asked to look in to test each)?

Superior rectus= elevation, adduction (look superior and laterally) Medial rectus= adduction (look medially) Inferior rectus= depression, some adduction (look inferiorly and laterally) Inferior oblique= elevation, abduction, lateral rotation (look superiorly and medially)

Which sinuses meet at the confluence of the sinuses at the internal occipital protuberance?

Superior sagittal, straight and transverse sinuses

Outline the course of the general visceral pre-ganglionic para efferents of the facial nerve:

Superior salivatory nucleus->greater petrosal n synapse in pterygopalatine ganglion->post-gang to lacrimal glands, chorda tympani fibres to submandibular ganglion->post-g to sublingual and submandibular glands

Where is Wernicke's area, and what is its relevance in audition?

Superior temporal gyrus, =auditory association cortex, for interpretation of auditory info, and giving it contextual significance (Wernicke's aphasia=fluent/receptive, impaired comprehension of language->fluent but unintelligible speech)

Why are infarcts more commonly seen in white matter?

Supplied by small BVs with narrow lumen. Grey matter has greater blood flow rate due to high metabolic demand(cell bodies carrying out protein synthesis)

Why are the Broca's area(inferior frontal gyrus), Wernicke's area(superior temporal gyrus) and primary motor and sensory cortices commonly affected by stroke?

Supplied by superficial divisions of the MCA. Broca's= superior division, Wernicke's= inferior division

Role of the visual association cortex?

Surrounds primary visual cortex. Interpretating visual images, recognition, depth perception, colour vision

Which tracts are damaged in lateral medullary syndrome?

Sympathetic fibres->Horner's syndrome Lateral spinothalamic (contralateral loss of temp and pain sensation) Spinocerebellar tract

Which spinal segments have a lateral horn swelling?

T1-L2, cell bodies of sympathetic motor neurones

What does lamina VII contain between T1-L2, and between S2-S4?

T1-L2= pre-ganglionic sympathetic neurones in lateral horn S2-S4= pre-ganglionic parasympathetic neurones

At what vertebral level does the thoracic cord terminate?

T8

What comprises the peripheral NS?

peripheral spinal nerves and cranial nerves(project from sensory and motor brainstem nuclei)

What cells are contained in the neural part of the retina? (see physiology for detail)

photoreceptors(rods and cones), neurones(2st order bipolar cell->ganglion cell->form optic nerve), glial cells, rich capillary network

What are the names of the 3 ducts of the cochlea?

scala vestibuli(perilymph), scala media(endolymph), scala tympani(perilymph). Scala vestibuli and tympani join at the helicotrema

Parkinson's, Huntington's, tardive dyskinesia, Hemiballismus

see BAB physiology cards

What is the general pathway of sensory information to where it is perceived?

sensory receptor->thalamus->cerebral cortex(consciously, subjectively perceived) or cerebellum (unconsious perception)

Describe the external acoustic meatus:

sigmoid shaped, from deep part of concha to tympanic membrane. Walls formed of auricular cartilage and temporal bone

Example of a subarachnoid haemorrhage and intracerebral haemorrhage?

subarachnoid=aneurysm in circle of willis intracerebral= rupture of a lenticulostriate branch of middle cerebral artery (most common in hypertension)

What are the muscles of mastication?

temporalis, masseter, medial and lateral pterygoids(1st pharyngeal arch)

What vessels does the anterior communicating artery connect at the most anterior point of the circle of Willis?

the L and R anterior cerebral arteries (they each course along corpus callosum)

What is the bony labyrinth?

the hollow cavity in inner ear, with membraneous labyrinth lining inside, containing vestibulocochlear organs.

What separates the vestibule from the middle ear?

the oval window. Vestibule communicates with cochlea anteriorly and semicircular canals posteriorly