PNB 3255 - Exam #1 - Class 6 - Cranial Nerves Lecture

Controls of the four of the six eye movement muscles, raises the upper eyelid, controls pupil diameter, and changes lens shape to focus images on the retina

CN 3 - Oculomotor Nerve

The cochlear portion of the vestibulocochlear nerve is embedded in the __ while the vestibular portion has its fibers embedded in the __

Cochlear Portion = *cochlea* Vestibular Portion = *semicircular canals of inner ear*

dysfunction in this cranial nerve will lead to a loss of hearing and/or tinnitus

Cochlear Portion of CN 8 - Vestibulocochlear Nerve

involved in the ability to determine pitch and the locations of sounds in space

Cochlear Portion of CN 8 - Vestibulocochlear Nerve

its proximal fibers are known as the spiral ganglion; embedded in the cochlea, they conduct the interpreted signals of sound to regions of the medulla, pons, and temporal lobe

Cochlear Portion of CN 8 - Vestibulocochlear Nerve

Patient with a lesion in left hypoglossal nerve will have atrophy of following muscle: Left half of tongue that protrudes to the left Left half of tongue that protrudes to the right Right half of tongue that protrudes to the right Right half of tongue that protrudes to the left

Left half of tongue that protrudes to the left

Name the extra-ocular muscle: elevates the superior (upper) eyelid

Levator palpebrae superioris

The obturator nerve arises from __ to __ (spinal nerves) and innervates __

L2 - L4 innervates sensory information in the inside of the lower thigh

The femoral nerve arises from __ to __ (spinal nerves) and innervates __

L2 - L4 innervates sensory information on the inside of the leg

When internuclear neurons which control contralateral medial rectus are affected that results in inability to move contralateral eye medially when trying to look toward the side of the lesion.

Lateral Conjugate Gaze Paralysis

Name the extra-ocular muscle: moves eye laterally (abducts it)

Lateral rectus

conducts sensory signals from the upper face: cornea, ciliary body, iris, lacrimal glands, conjunctiva, nasal mucosal membranes, eyelids, eyebrows, forehead, and nose bridge

Ophthalamic Branch of Trigeminal Nerve

Which part of the oculomotor system is this? Edinger-Westphal Nucleus: close to the midline of the rostral midbrain, dorsal to the oculomotor neurons; projects to the ipsilatearl cilliary ganglion and innervates sphincter pupillae and the cilliary muscles; important for the light reflex

Parasympathetic Nucleus

Name the extra-ocular muscle: depresses eye ball, helps rotate the eye medially (inward)

Superior oblique

Name the extra-ocular muscle: elevates and medially (inward) rotates eye ball

Superior rectus

Taste sensation travels from CNs __ to the __ of the brainstem, then to the __ of the thalamus and finally to the hypothalamus, amygdala, insula and frontal cortex, etc.

Taste sensation travels from CNs *7, 9, 10* to the *solitary nucleus* of the brainstem, then to the *VPM* of the thalamus and finally to the hypothalamus, amygdala, insula and frontal cortex, etc.

Glossopharyngeal nerve lesion (ie lesion of the solitary nucleus) would result in loss of __ sensation in the __

Taste, touch, temperature, pain in the posterior third of the ipsilateral side of the tongue

The Edinger-Westphal nucleus contains __ fibers that merge with the __ to form the __. The EW in the __ supply the sphincter pupillae muscles of the pupil.

The Edinger-Westphal nucleus contains *general visceral efferents (GVEs)* fibers that merge with the *general somatic motor efferents (GSEs)* to form the *oculomotor nerve*. The EW in the *oculomotor nerve* supply the sphincter pupillae muscles of the pupil.

What is the Final Common Pathway?

The abducens nucleus of cranial nerve 6 comprises pools of motoneurons and interneurons. For example, left CN 6 motoneurons innervate the left eye's lateral rectus muscle, which drives the left eye to the left (laterally). The left abducens interneurons project fibers across midline that ascend the right medial longitudinal fasciculus and synapse the right oculomotor nucleus of cranial nerve 3 in the midbrain. The right oculomotor nucleus innervates the right eye's medial rectus muscle and drives the right eye to the left (medially). Thus, through the use of the MLF, the eyes can be coordinated to gaze to the left.

Motoneurons innervating the extra-ocular muscles CAN NOT be found in The facial nucleus The abducens nucleus The trochlear nucleus The oculomotor nucleus

The facial nucleus

a stimulation of the parasympathetic functions of the vagus nerve causes a sudden drop in blood pressure and heart rate which can lead to syncope (fainting) this response can be caused by the valsalva maneuver, acute cholecystitis/gastritis, severe emotional stress, abdominal straining ("bearing down") during defecation, hyperthermia, swallowing, or coughing

Vasovagal Response (Vasovagal syncope often is caused by a simultaneous intensification of parasympathetic tone and withdrawal of sympathetic tone)

Ocular nucleus located in the midbrain, at an intercollicular level between the superior colliculus and inferior colliculus

Trochlear nucleus

Taste sensation facial nerve roots

Two roots of facial nerve join geniculate ganglion, and then go either into greater petrosal nerve- important for sensation of taste in soft palate, or chorda tympani nerve- taste fibers important for taste sensation of anterior 2/3 of tongue.

Since the __ nerve controls the activity of muscles of the larynx, pharynx and activities of heart, lungs, abdominal organs, bilateral lesion of this nerve is lethal

Vagus nerve

conveys information from the inner ear about the orientation and movement of the head to help keep equilibrium (i.e. balance)

Vestibular Portion of CN 8 - Vestibulocochlear Nerve

dysfunction in this cranial nerve will lead to a false sensation of motion (vertigo), motion sickness, or an involuntary movement of the eye (nystagmus)

Vestibular Portion of CN 8 - Vestibulocochlear Nerve

its proximal fibers are known as vestibular ganglion; embedded in the semicircular canals of the inner ear , they conduct the interpreted signals of canal orientation to the pons, medulla oblongata, medulla spinalis (spinal cord), and vermis of the cerebellum.

Vestibular Portion of CN 8 - Vestibulocochlear Nerve

Which nerve has only sensory function? Trigeminal Trochlear Abducens Vestibulocochlear

Vestibulocochlear

Trochlear nerve fibers innervate the muscles of the ipsi-/contra-lateral eye

contralateral (nerve fibers emerge from the contralateral nucleus and decussate superior to the midbrain)

Internuclear neurons that travel between the abducens nucleus and the MLF control the ipsi-/contra-lateral __ muscle.

contralateral medial rectus muscle

The muscles of the face, head and neck are controlled by the __ system, which terminates on motor neurons within brainstem motor nuclei.

corticobulbar

__ fibers in the facial nerve supply sensation to the skin of the external ear

cutaneous

The hypoglossal nucleus lies between the __ and __

dorsal nucleus of the vagus nerve & the midline of the medulla

Lesions in the trochlear nerve would result in the inability to look __. Attempted movement in these directions may cause __

downward and laterally in the contralateral eye vertical diplopia (double vision)

What is ptosis?

drooping eyelid

The motor fibers in the spinal root of the accessory nerve form the __ of the accessory nerve

external ramus **see diagram on slide 44 of Class 6 ppt

Horner's syndrome is due to a lesion along pathway from the __ to the __

from the hypothalamus to the preganglionic sympathetic neurons in the interomediolateral cell column in C8-T2 portion of the spinal cord

partial loss of smell

hyposmia

Cells with visceral functions (ie __) end up near the __ in the spinal cord

ie GVA & GVE near sulcus limitans

Name the extra-ocular muscle: depresses and laterally rotates eye ball

inferior rectus

injury to this nucleus causes loss of contralateral eye adduction. (ie if the R nucleus is lesioned, the L eye cannot be adducted (move medially))

injury to abducens *interneurons*

lesion to this nucleus results in loss of ipsilateral eye abduction (ie if the R nucleus is lesioned, the R eye cannot be abducted (move laterally))

injury to abducens *motoneurons*

Since the Edinger-Westphal nucleus innervates the __ and __, it is very important for the __ reflex of your eye

innervates the sphincter papillae & ciliary muscle important for the light reflex (adjusting your pupil for different amounts of light)

The motor fibers in the medullary root of the accessory nerve form the __ of the accessory nerve

internal ramus **see diagram on slide 44 of Class 6 ppt

The Edinger-Westphal Nucleus is a para/sympathetic nucleus

parasympathetic

__ fibers in the facial nerve go to ganglia that supply the lacrimal, submandibular, and sublingular muscles.

preganglionic *parasympathetic* fibers

Where is the Edinger-Westphal nucleus located?

rostral midbrain at the level of the superior colliculus EW nucleus is posterior to motor oculomotor nucleus

What information to afferents carry in the vagus nerve?

sends general sensory fibers (pain) to dura, larynx, trachea, bronchi and esophagus

The hypoglossal nucleus receives afferents from the __ and __ for coordinating the tongue in reflex movements of swallowing, chewing, and sucking

solitary nucleus & sensory trigeminal nucleus (both used by the vagus and glossopharyngeal nerves which are involved in innervating the pharynx and larynx and taste in the tongue and epiglottis)

The nucleus ambiguus receives afferents from the __ and __, which are involved in reflexes for coughing, gagging, and vomiting.

solitary nucleus & spinal trigeminal tract

GSA, GVA, GVE, GSE are found in the __

spinal cord & medulla

The information carried by the vagus and glossopharyngeal cranial nerves is apart of the __ tract, which contains information about __

spinal trigeminal tract - receives information about deep/crude touch, pain, and temperature from the ipsilateral face

Where does the decussation of the trochlear nerve fibers occur?

superior to midbrain

Where do nerve fibers of the trochlear nerve decussate?

superior to the midbrain

a painful, brief facial spasm or tic travels down the face along the route of the __ nerve when the __ nerve is damaged

trigeminal neuralgia trigeminal nerve damaged

T/F: herpes zoster can cause sensory loss in the trigeminal nerve

true

What Type of Cranial Nerve? -sensory -related to receptors for visceral organs, including thoracic, abdominal, and pelvic viscera, in head and neck

General Visceral Afferent (GVA)

What Type of Cranial Nerve? -motor -motor fibers that innervate smooth muscle, cardiac muscle, and glands.

General Visceral Efferent (GVE)

CN 3 contains __ and __ fibers

GSE & GVE

SVE, SVA, and SSA nerves are found in the __

medulla oblongata

left corticobulbar lesion will result in paralysis of __ this a U/L MN disease

muscles that control the *lower right* quadrant of the face UMN disease (A and B on diagram)

What are the nuclei of origin for the extra-ocular eye muscles' cranial nerves (3, 4, and 6)?

ocular motor nuclei which contain motor neurons and internuclear nuclei

Lesions of the trigeminal nuclei in the brainstem cause ipsi/-contra-lateral loss of facial sensation to pain and temperature because __

*ipsi*lateral because the primary sensory fibers do not cross before entering the nucleus

Which of following cranial nerves is not related to eye muscle movements? oculomotor trigeminal abducens trochlear

trigeminal

What are the branches of the spinal accessory nerve (CN 11)?

1. Medullary Branch 2. Spinal Branch

What CNs are at the ponto-medullary junction?

Abducens Facial Vestibulocochlear

Which nerves are purely sensory nerves?

CN 1 - Olfactory CN 2 - Optic CN 8 - Vestibulocochlear

-branches of the nerve conduct sensory signals from the anterior two thirds of the tongue (for taste sensation), upper pharynx, and earlobe -conducts voluntary motor signals to the face muscles & stapedius muscle in the middle ear and parasympathetic signals to the salivary and lacrimal glands

CN 7 - Facial Nerve

What is the main parasympathetic nucleus in the oculomotor system?

Edinger-Westphal Nucleus

Fibers from the __ nerve end in the spinal trigeminal tract and spinal trigeminal nucleus

Glossopharyngeal

Name the extra-ocular muscle: elevates and laterally rotates eye

Inferior oblique

The oculomotor nerve supplies the contra-/ipsi-lateral muscles of the eye.

Ipsilateral -> if left oculomotor nerve is damaged, left eye will present with symptoms

Which part of the oculomotor system is this? Provides motor innervation of the extra ocular muscles

Somatic Motor Nucleus

What Type of Cranial Nerve? -mediate the special senses: sight, hearing, smell

Special Somatic Afferents (SSA)

Dysfunction in this nerve results in face muscle atrophy and/or a syndrome known as __ neuralgia

Trigeminal Nerve

Which nerve has both motor and sensory function? Vagus Optic Oculomotor Hypoglossal

Vagus

Where is the chief/principal trigeminal nucleus?

pons

Lesion of the __ nerve would result in swallowing difficulties

vagus nerve

When the medial longitudinal fasciculus is injured, the ipsi-/contra-lateral eye is unable to ab-/ad-duct and the opposite eye will have __ when it ab-/ad-ducts

*ipsi*lateral eye is unable to *ad*duct and the opposite eye will have *horizontal nystagmus* (uncontrolled, repetitive movements) when it *ab*ducts ie if the R MLF is injured, the R eye will not be able to move inward when the left eye (as controlled by the abducens) is moved outward (abducted)

They all arise from the midbrain and pons to provide motor control of the six extraocular muscles: the levator palpebrae superioris (controls the eyelid) and the ciliary muscles (controls pupillary constriction and lens accommodation).

CN 3 (oculomotor) CN 4 (trochlear) & CN 6 (abducens)

Damage to the oculomotor nerve causes __ (5 things)

1. Lateral Strabismus: medial rectus paralysis & lateral rectus is unopposed -. eye moves laterally 3. Diplopia (double vision) 4. Ptosis (drooping eyelid) -> due to paralysis of levator palpabrae 5. Pupil is dilated -> damage of the parasympathetic part of the oculomotor nerve - to the Edinger-Westphal nucleus

Which branches of the trigeminal nerve are sensory? Motor?

1. Ophthalamic - sensory only 2. Maxillary - sensory only 3. Mandibular - sensory & motor

What is lesioned in medial medullary syndrome?

1. Pyramids -> contralateral motor loss (hemiplegia) 2. MLS -> contralateral sensory loss 3. Hypoglossal nerve -> ipsilateral loss of tongue muscle innervation

What are 2 key indicators of brainstem stroke (ie medial medullary syndrome)?

1. ipsilateral cranial nerve signs (tongue paralysis) 2. contralateral body signs (hemiplegia and lemniscal sensory loss)

1. Large diameter fibers for discriminative touch end in the __ trigeminal nucleus. 2. Fibers which send information for light touch end in the __ trigeminal nucleus

1. pontine 2. spinal

The spinal accessory nerve (CN 11) consists of __ branches

2

Which cranial nerves are involved in eye movement and pupillary constriction?

3, 4, 6

How many cranial nerves are attached to the medulla? Which are they?

7 Cranial Nerves: Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Hypoglossal Accessory

The sense of taste is conveyed by CN(s) __

7, 9, 10

What neurotransmitter does the vagus nerve use to control heart beat?

ACh -> slows down heart rate (remember the vagus nerve has PARAsympathetic fibers that are involved in REST and digest)

Which nerves contain parasympathetic fibers?

CN 3 - Oculomotor CN 7 - Facial CN 9 - Glossopharyngeal CN 10 - Vagus (also sacral spinal nerves S2, S3, and S4)

This ocular nucleus is located beneath the fourth ventricle in the caudal portion of the pons, medial to the sulcus limitans

Abducens nucleus

Which nerve innervates muscles that make head to turn? Hypoglossal Glossopharyngeal Facial Accessory

Accessory

The __ nerve originates in the nucleus ambiguus, together with CN vagus and glossopharyngeal, to innervate the muscles of the soft palate, pharynx, larynx and esophagus.

Accessory Nerve (purely motor)

Afferent fibers from the pharynx and larynx send info from the periphery and terminate in the __ for CN(s) __. Cell bodies for these afferent fibers are localized in the __

Afferent fibers from the pharynx and larynx send info from the periphery and terminate in the *nucleus of solitarius* for CN(s) *vagus* & *glossopharyngeal*. Cell bodies for these afferent fibers are localized in the *superior & inferior ganglion* **see diagram on slide 41 of Class 6 ppt

Anosmia (loss of smell) or hyposmia (partial loss of smell) can be caused by tumors or growths, which compress the __, or by damage to the __ bone that causes shearing of the nerves in the __.

Anosmia (loss of smell) or hyposmia (partial loss of smell) can be caused by tumors or growths, which compress the *ophthalmic bulb*, or by damage to the *ethmoid bone* that causes shearing of the nerves in the *cribriform plate*

Why doesnt the upper part of the face lose sensation when you have an UMN lesion of the corticobulbar tract?

Because there is a bilateral (two yellow neurons) projection to the upper face

paralysis of facial motor neurons that may be caused by inflammation of this nerve as it runs through bone

Bell's Palsy - CN 7 - Facial Nerve

Name the Disorder: -Lower motoneuron lesion, -Weakness of all muscles of the ipsilateral face -Affected activities: blinking & closing of the eyes, smiling, frowning, lacrimation, salviation, flaring nostrils, raising eyebrow -Can be induced by virus (ie herpes zoster) -> treatment = corticosteroids -Goes away after a few weeks -Sometimes recovery is "off" target (ie crocodile tear syndrome: lacrimation (crying) instead of salivation when seeing/eating food) What CN is affected?

Bell's Palsy - Facial Nerve

Fibers from this nerve descend with the common carotid artery and jugular vein to innervate several muscles and organs. Parasympathetic fibers innervate all thoracic organs (e.g., respiratory, cardiac) and all digestive organs before the transverse colon. A few fibers also conduct sensory signals from the dorsal external ear

CN 10 - Vagus Nerve

Motor signals from this CN are conducted to several skeletal muscles involved in speech (via the recurrent laryngeal nerve branch), swallowing, and peristalsis Also is involved in a diverse set of motor, sensory, and parasympathetic functions including: blood pressure, heart rate, sweating, glandular secretion, aortic chemoreception, and opening of the larynx during breathing

CN 10 - Vagus Nerve

Which nerves are purely motor nerves?

CN 11 - Spinal Accessory CN 12 - Hypoglossal

Asymmetry, atrophy, or fasciculation of shrugs and head turns may imply damage to this nerve

CN 11 - Spinal Accessory Nerve

controls muscles of the neck and upper back and permits voluntary swallowing

CN 11 - Spinal Accessory Nerve

Asymmetry, atrophy, or fasciculation of the protruding tongue may imply damage to this nerve

CN 12 - Hypoglossal Nerve

arises from the medulla and contributes nerve fibers to the muscles of the tongue

CN 12 - Hypoglossal Nerve

A patient with damaged to CN __ may have an eye that looks inferolaterally ("down and out"), a drooping eyelid (ptosis) and/or pupillary dysfunction.

CN 3 - Oculomotor nerve (dysfunction prevents almost all the extraocular eye movements (b/c CN3 controls 4/6 extra-ocular eye muscles) except eyeball abduction (lateral movement) and intorsion (inward movement))

The oculomotor system involves CNs __ and has 2 parts, including __

CN 3, 4, 6 2 Parts: 1. Somatic Motor Nucleus 2. Parasympathetic Part

These nerves contain GSE fibers

CN 3, 4, 6, 12

__ CNs' nuclei of origin are located adjacent to midline near the cerebral aqueduct or in the floor of fourth ventricle and these CNs contain GSE fibers

CN 3, 4, 6, 12

controls the superior oblique muscle

CN 4 - Trochlear Nerve

dysfunction of this cranial nerve generally causes the eye to drift upward (due to loss of intorsional and some downward movement) and produces a double-visual field patients will often move their heads inward (giving a "pathetic" appearance) or far to the side to re-align their visual fields

CN 4 - Trochlear Nerve

this nerve is named for the pulley-shaped ligament through which the superior oblique muscle passes to allow the eye to look down and outward (intorsion)

CN 4 - Trochlear Nerve trochlea means pulley!

Which nerves are sensory & motor nerves?

CN 5 - Trigeminal CN 7 - Facial CN 9 - Glossopharyngeal CN 10 - Vagus

Provides tactile information (such as pressure, temperature and pain of the face and mouth) and activates the muscles of mastication

CN 5 - Trigeminal Nerve

CN responsible for transmission of touch, pain, proprioception and temperature information from the head to the cortex, cerebellum and reticular formation

CN 5 - Trigeminal Nerve System

Moves the eyeball laterally

CN 6 - *Abduc*ens (moving the eye laterally = *abduc*ts the eye!!)

controls the lateral rectus muscle

CN 6 - Abducens Nerve

dysfunction in this cranial nerve prevents the eyeball from being able to move laterally

CN 6 - Abducens Nerve

Dysfunction in this nerve results in asymmetrical loss of facial expression, taste, crying, and salivation may occur.

CN 7 - Facial Nerve

The __ nerve passes through several canals in the temporal bone; it runs through more distance of bone than any other nerve.

CN 7 - Facial Nerve

this nerve permits deep pressure sensation over the face and receive taste information from the receptors along the anterior two-thirds of the tongue also controls the muscles of facial expression in the scalp, face and near the ear and stimulates the flow of saliva and tears

CN 7 - Facial Nerve

fibers from these cranial nerves conduct motor signals to the constrictor muscles of the pharynx, the stylopharyngeus, and the larynx.

CN 9 (Glossopharyngeal) CN 10 (Vagus) CN 11 (Spinal Accessory)

Which CNs emerge on the lateral side of the dorsal medulla dorsal (behind) to the olives and leave the skull at the jugular foramen?

CN 9 - Glossopharyngal CN 10 - Vagus CN 12 - Accessory

dysfunction in these CNs will often cause asymmetrical (or absent) gag reflex; patients may have difficulty swallowing or phonating

CN 9 - Glossopharyngeal CN 10 - Vagus

Name the CN: -mediates general sensation to the area of the palatine tonsils, the oral mucosa behind the tonsillar pillars, and root of the tongue, the auditory canal and inner surface of the tympanic membrane -also mediates *chemoreception* (detection of blood CO2 levels and acidity) and *baroreception* (detection of blood pressure) -supplies posterior 2/3 of tongue, vagus taste buds on the epiglottis

CN 9 - Glossopharyngeal Nerve

This nerve is abundant in sensory fibers, but it also contains motor fibers It relays sensory information from the pharynx and the soft palate, provides taste sensation from the posterior third of the tongue, and contains receptors that monitor blood pressure and gas concentrations within blood vessels

CN 9 - Glossopharyngeal Nerve

innervates the parotid salivary glands and the tongue and the pharyngeal muscles

CN 9 - Glossopharyngeal Nerve

What nerves are branchiomeric? Are the sensory, motor, or both?

CNs 5, 7, 9, 10 = sensory & motor CN 11 = motor

the parasympathetic pre-ganglionic nucleus that innervates the iris sphincter muscle and the ciliary muscle

Edinger-Westphal Nucleus

Where are GSA, GVA, GVE, and GSE nerves localized in the neural tube?

GSA and GVA are localized in alar plates GVE and GSE are in basal plate **See diagram on slide 7 in Class 6 ppt

Neurons involved in reflex movements in response to visual stimuli, proprioceptive information from eye muscles, vestibular system, cortex and cerebellum.

Gaze Neurons (GSE fibers)

What Type of Cranial Nerve? -sensory -related to receptors for pain, temperature, touch, pressure, proprioception in skin, muscles and joints

General Somatic Afferent (GSA)

What Type of Cranial Nerve? -motor -these fibers arise from motor neuron cell bodies in the ventral horns of the gray matter within the spinal cord. They exit the spinal cord through the ventral roots, carrying motor impulses to *skeletal muscle* through a neuromuscular junction

General Somatic Efferent (GSE)

General visceral afferent (GVAs) neurons in this nerve are important for reflex regulation in cardiovascular, respiratory and alimentary function

Glossopharyngeal Nerve

Afferents in the __ nerve for touch sensation in the pharynx are important for gag reflex

Glossopharyngeal Reflex

Name the Disorder: -caused by viral infection of ganglia (virus also causes chicken pox) -skin eruption in the area of distribution of dorsal root of this cranial nerve -treatment: capsaicin (component of chili peppers) - used as ointments, nasal sprays, or dermal patch relieves pain caused by this disorder

Herpes Zoster (commonly known as shingles) trigeminal nerve disorder Further info: Ophthalmic division (V1) of the trigeminal nerve is most commonly affected. Vesicles appear along the path of dermatome (Fig. 1). Macules and papules progress into vesicles and pustules that eventually dry, leaving a crusting appearance after 5-7 days. Vesicles in the cornea may lead to ulceration. Ramsay Hunt syndrome, which induces facial palsy, loss of taste, buccal ulceration and appearance of rash in the auditory canal on the affected side; intraoral mucosal ulceration may also be part of the spectrum with or without full manifestation of Ramsay Hunt syndrome

syndrome that develops from injury to anywhere along the C8-T2 sympathetic pathway lesion interrupts the pathways from the brain (hypothalamus) to the preganglionic sympathetic neurons in the intermediolateral cell column results in ipsilateral drooping of eyelid (ptsosi), constriction of ipsilateral pupil, loss of sweating on left side of body and face,

Horner's Syndrome

If corticobulbar fibers innervating facial nucleus are damaged, __ paralysis of the ipsi-/contra-lateral upper/lower face occurs because the upper/lower face receives __ this a U/L MN disease

If corticobulbar fibers innervating facial nucleus are damaged, __ paralysis of the *contralateral* *lower* face occurs because the *upper* face receives *bilateral projections* ie left corticobulbar lesion results in paralysis of the muscles that control the lower right quadrant of the face UMN disease

If the right oculomotor nucleus were damaged, the __ eye would be unable to move in the __ directions. The __ eyelid would not close/would droop. The eye would be ab/ad-ducted The pupil would be constricted/dilated because __.

If the right oculomotor nucleus were damaged, the *right* eye would be unable to move in the *downard, upward, medial, or extorsion (external rotation)* directions. The *right* eyelid *would droop*. The eye would be *ab*ducted (moved outward) The pupil would be *dilated* because *of loss of Edinger-Westphal nucleus*.

What are the 3 parts of the spinal trigeminal nucleus?

Information of pain, temperature and light touch go through spinal trigeminal tract to spinal trigeminal nucleus 3 Parts: 1. Pars Caudalis - from pyramidal decussation to spinal segment C3; pain, temperature 2. Pars Interpolaris - inferior olive nuclei to pyramidal decusssation 3. Pars Olaris - from pars interpolaris to pontine trigeminal nucleus

Injury or compression of an optic nerve distal to the chiasm will affect the ipsi-/contra-lateral visual field transmitted from one eyeball. Damage or compression of __ often affects both visual fields either medially (binasal) or laterally (bitemporal). Damage __ causes loss of vision from one eyeball but affects the entire merged contralateral visual field. Other diseases affecting the optic nerve include: glaucoma, optic neuritis and anterior ischemic optic neuropathy.

Injury or compression of an optic nerve distal to the chiasm will affect the *ipsi*lateral visual field transmitted from one eyeball. Damage or compression *within the optic chiasm* often affects both visual fields either medially (binasal) or laterally (bitemporal). Damage *proximal to the chiasm* causes loss of vision from one eyeball but affects the entire merged contralateral visual field. Other diseases affecting the optic nerve include: glaucoma, optic neuritis and anterior ischemic optic neuropathy.

What is one of the functions of trigeminal nerve? Innervates sternocleidomastoid and trapezius muscles Innervates muscles of tongue Innervates muscles of mastication Innervates muscles involved in swallowing

Innervates muscles of mastication

conducts sensory signals from the lower and lateral face: lower lip skin, chin, ear, lower jaw teeth and the tongue also conducts motor signals to several swallowing and chewing muscles such as: temporalis, masseter, pterygoids, anterior part of the digastric muscles , tensor tympani, and tensor veli of the palatine muscles

Mandibular Branch of Trigeminal Nerve

conducts sensory signals from the middle face: cheek, lower eyelid, lateral nose, upper jaw, teeth, palate, nasal cavity, and sinuses (e.g., pterygoid region, maxillary sinus)

Maxillary Branch of Trigeminal Nerve

What happens when the abducens nerve/nucleus is lesioned?

Medial Strabismus: the affected eye (on the same side as the lesion) will deviate medially as action of the medial rectus muscle (controlled by CN 3) will not be opposed lateral rectus muscle anymore when looking straight on; the person will also be *unable* to *ab*duct the eye when *looking toward the affected side*

Name the Branch of the Spinal Accessory Nerve: fuses with the vagus nerve and innervates voluntary swallowing muscles of the soft palate, pharynx, and vocal cords

Medullary branch

Motor fibers for CN(s) __ originate in the nucleus ambiguus and innervate the muscles of the __

Motor fibers for CN(s) *vagus & glossopharyngeal* originate in the nucleus ambiguus and innervate the muscles of the *pharynx* (both) and *larynx* (vagus only) **see diagram on slide 41 of Class 6 ppt

Nerve fibers embedded in the mucosa of the nasal cavity travel through a portion of the __ bone called the __ to meet with the __. Signals are transmitted to and from the __, which pass through the frontal lobes, to connect with several regions of the temporal lobe.

Nerve fibers embedded in the mucosa of the nasal cavity travel through a portion of the *ethmoid bone* called the *cribriform plate* to meet with the *olfactory bulbs*. Signals are transmitted to and from the *olfactory tracts*, which pass through the frontal lobes, to connect with several regions of the temporal lobe.

Nerve fibers from the retinae emerge from the posterior eyeballs as the __ and decussate (i.e., "cross") at the __ becoming the __. The __ travel through the __ in the __ bone. Signals are conveyed through many tracts before reaching the primary visual cortex in the occipital lobe.

Nerve fibers from the retinae emerge from the posterior eyeballs as the *optic nerves* and decussate (i.e., "cross") at the *optic chiasm* becoming the *optic tracts*. The *optic tracts* travel through the *optic foramina* in the *sphenoid bone*. Signals are conveyed through many tracts before reaching the primary visual cortex in the occipital lobe.

The __ is situated dorsal to the inferior olivary nucleus. Axons from this nucleus join glossopharyngeal and vagus nerve axons to make the cranial root of the accessory nerve. This nucleus supplies muscles of the soft palate, pharynx, larynx, and esophagus.

Nucleus Ambiguus

Often lesions of the trigeminal nucleus in the pons or medulla also involve the nearby __. This combination of spinal trigeminal and spinothalamic tract involvement in lateral brainstem lesions leads to a well-recognized pattern with sensory loss to __ in the face ipsi-/contra-lateral to the lesion and ipsi-/contra-lateral in the body

Often lesions of the trigeminal nucleus in the pons or medulla also involve the nearby *spinothalamic tract*. This combination of spinal trigeminal and spinothalamic tract involvement in lateral brainstem lesions leads to a well-recognized pattern with sensory loss to *pain and temperature* in the face *ipsi*lateral to the lesion, but in the body *contra*lateral to the lesion because the spinothalamic tract crosses at the level of the spinal cord it is designated for, so any lesion above that level will result in loss of sensation on the contralateral side.

What are the 3 trigeminal nuclei? What info does each carry?

Pontine nucleus - main sensory nucleus; has large diameter fibers for discriminative *touch and pressure* Spinal Trigeminal nucleus - info for *pain, temp* and light touch Mesencephalic nucleus - myelinated axons; involved with reflex *proprioception* of the periodontium (gums) and of the muscles of mastication in the jaw that functions to prevent biting down hard enough to lose a tooth

The R hypoglossal nerve supplies the R/L side of the tongue and the tongue will push out to the R/L

R hypoglossal nerve -> innervates R side of tongue -> tongue protrudes to R if R hypoglossal nerve is lesioned (ipsilateral innervation)

Which of the following is not a disease of motor neurons? Bell's palsy Amyotropic lateral sclerosis Lateral strabism Shingles

Shingles

What Type of Cranial Nerve? -branchiomotor -effector innervation of skeletal muscle in larynx, pharynx and face- swallowing (IX,X), chewing (V), facial expression (VII), vocal sounds (X), turning head (XI)

Special Visceral Efferent (SVE)

What Type of Cranial Nerve? -mediate taste

Special visceral afferents (SVA)

Name the Branch of the Spinal Accessory Nerve: fibers originate in the lateral gray horns of C1-C5 to innervate the sternocleidomastoid (neck muscle that turns head) and trapezius muscle (dorsal shoulder muscle)

Spinal Branch

The oculomotor nerve (CN 3) emerges from the lateral/medial side of the __ (brainstem structure) in the __ (location in midbrain), travels to the __ where it branches to supply the __ muscles.

The oculomotor nerve (CN 3) emerges from the *medial* side of the *cerebral peduncles* in the *midbrain*, and travels to the *cerebral peduncles* where it branches to supply the *superior rectus, medial rectus, inferior rectus, inferior oblique, and levator palpabrae* muscles.

In this condition, patients experience recurrent episodes of brief severe pain lasting from seconds to a few minutes, most often in the distribution of V2 or V3. Attacks usually begin after age 35. Painful episodes are often provoked by chewing, shaving, or touching a specific trigger point on the face. Neurologic exam, including facial sensation, is normal.

Trigeminal Neuralgia

Name the Disorder: -caused by demyelination of axons of the sensory root which is caused by pressure of small aberrant artery -pain in skin supplied by one of the branches of trigeminal nerve -treatment: anti-epileptic drugs

Trigeminal Neuralgia

The only nerve to have its nuclei originate on the contralateral side to the side of the body that it innervates

Trochlear nerve (ie left trochlear nucleus innervates the right eye)

Example of One-And-A-Half Syndrome

When the left abducens nucleus is injured, there is loss of gaze toward the side of the lesion (left gaze palsy), and when the adjacent medial longitudinal fasciculus is injured, the ipsilateral eye (the left eye) can't adduct. Thus, when both the abducens nucleus and the adjacent medial longitudinal fasciculus are injured, the only intact movement is right eye abduction (and it has nystagmus from the left medial longitudinal fasciculus injury); thus, one-and-a-half of the two complete eye movements are impaired, so the injury pattern is called one-and-a-half syndrome.

Facial motor nerves loop over __ nucleus

abducens *see slide 34 on Class 6 ppt for diagram

The __ nerve is often the first cranial nerve to lose function in presence of increased intracranial pressure

abducens nerve

Lesions of the __ and __ are called One-And-A-Half syndrome.

abducens nucleus & MLF (medial longitudinal fasciculus)

What is lesioned in one-and-a-half syndrome?

abducens nucleus/cranial nerve -> cannot abduct (move outward) ipsilateral eye MLF on the same side as the lesioned abducens nucleus/cranial nerve -> cannot adduct (move inward) ipsilateral eye so ipsilateral eye has no horizontal gaze movement at all ----- also lost: internuclear region (part of abducens nucleus) that projects contralaterally and innervates medial rectus of contralateral eye -> contralateral eye cannot be adducted so, we've lost "one and a half" movements -> only movement that is remaining is the abduction of the contralateral eye

Lesion of the abducens *moto*neurons would result in loss of the ability to ab/ad-duct the ipsi-/contra-lateral eye

abduct ipsi-lateral eye (fibers from the abducens nucleus innervate the ipsilateral eye and the abducens innervates the lateral rectus muscle, allowing your eye to be abducted)

Lesion of CN3 will result in loss of all eye movements except __

abduction (lateral movement) - done by abducens (CN 6) & intorsion (internal rotation) - done largely by trochlear (CN 4)

a complete abducens injury would result in loss of __. ie in a left abducens nucleus injury, the eyes would be unable to __

ability to gaze to the side unable to gaze to the left

Motor neurons for sternocleidomastod and trapezius muscle are located in dorsal/ventral horns of spinal cord, in __ nucleus of dorsal/ventral horn

accessory nucleus of the ventral horn

Lesion of the abducens *interneurons* would result in loss of the ability to ab/ad-duct the ipsi-/contra-lateral eye

adduct contralateral eye (interneurons send info from one abducens nucleus up the MLF to the opposite oculomotor nucleus to adduct the opposite eye so both of your eyes can gaze in the same direction)

What do CNs 5, 7, 9, and 10 have in common?

all innervate striated muscles of the branchial arch

total loss of smell

anosmia

What are the 2 sensory branches of the femoral nerve?

anterior femoral cutaneous nerve (shown as just femoral nerve in diagram) saphenous nerve

Where does the hypoglossal nerve exit the brainstem?

between the pyramids and inferior olivary nuclei of the medulla

A combination of ipsilateral cranial nerve signs (tongue paralysis) and contralateral body signs (hemiplegia and lemniscal sensory loss) is a key indicator of a __

brainstem stroke (medial medullary syndrome)

Where is the facial motor nucleus localized?

caudal pons

Where is the nucleus for the abducens nerve located?

caudal pons at the floor of the 4th ventricle

In addition to fibers that innervate the lateral rectus muscle, what other fibers are found in the abducens nucleus? Why are these necessary?

internuclear neurons which cross to contralateral nucleus and travel rostrally to oculomotor sub-nucleus that supplies medial rectus muscle **you need the lateral movement controlled by the abducens nerve to be coordinated with the medial movement controlled by the oculomotor nerve so that both eyes remain fixed on the same object, preventing double vision!!

When the medial longitudinal fasciculus is injured, the ipsilateral eye is unable to adduct. This is called an __

internuclear ophthalmoplegia (or MLF syndrome)

Abducens nerve fibers innervate the ipsi-/contra-lateral eye

ipsilateral eye

What is Weber syndrome?

ipsilateral oculomotor nerve (CN 3) palsy and contralateral hemiparesis or hemiplegia (contralateral pyramdial tract lesioned) caused by stroke in the midbrain as a result of occlusion of the paramedian branches of the posterior cerebral artery or of basilar bifurcation perforating arteries

Lesion of facial motor nucleus results in flaccid paralysis of all facial muscles on the ipsi-/contra-lateral side of the injury for quadrant/half/whole face this a U/L MN disease

ipsilateral side of the injury for *half* the face LMN disease (ie Bell's palsy) (C on diagram)

Damage of the hypoglossal nerve causes weakness on the ipsi-/contra-lateral side of the __. This would be a(n) UMN/LMN lesion.

ipsilateral side of the tongue affected LMN lesion

where does the abducens nerve exit the brainstem?

junction of the pons-pyramids (of the medulla)

Which muscle is not innervated by oculomotor nerve? medial rectus lateral rectus inferior oblique superior rectus

lateral rectus

This would constitute a bilateral lower motor neuron lesion. The patient would experience a flaccid paralysis of the skeletal muscles related to the lesioned spinal segment.

lesion of both ventral horns

nerve pathways transmit visual information to the brain; signals from the visual fields of each eyeball are ultimately merged into a single visual field and are, additionally, processed by brain structures involved in a diverse set of functions (e.g., memory, emotion, spatial awareness)

optic nerve

this tract connects the three extra-ocular motor nuclei (abducens, trochlear, and oculomotor) into a single functional unit to integrate eye movement information and control horizontal gazing it is also an integral component of saccadic eye movements

medial longitudinal fasciculus

Where are gaze neurons located? Why are these cells important?

medial longitudinal fasciculus - this tract connects the three extra-ocular motor nuclei (abducens, trochlear, and oculomotor) into a single functional unit to control horizontal gazing.

When both __ tracts are injured, neither eye can adduct - the right eye can't turn horizontally to the left and the left eye can't turn horizontally to the right This is called __

medial longitudinal fasciculus tracts injured Bilateral Internuclear Ophthalmoplegia

Name the extra-ocular muscle: adducts (moves inward) eye

medial rectus

The sensory and parasympathetic preganlionic axons of the facial nerve are located in the __

nervus intermedius

a vision condition in which the eyes make repetitive, uncontrolled movements

nystagmus - dysfunction of Vestibular Portion of CN 8 - Vestibulocochlear Nerve

The cranial nerves containing GVE fibers include the __.

oculomotor nerve (CN III) facial nerve (CN VII) glossopharyngeal nerve (CN IX) vagus nerve (CN X)

nerve pathways allow for the sense of smell; signals will ultimately interact with areas of the brain involved in a diverse set of functions (e.g., memory, emotion, taste)

olfactory nerve (1)

When both the abducens nucleus and the adjacent (same side) medial longitudinal fasciculus are injured, the only intact movement is ipsi-/contra-lateral eye ab-/ad-duction (and it has nystagmus from the MLF injury); the ipsi-/contra-lateral eye can neither abduct nor adduct. This syndrome is called __

only intact movement = *contra*lateral eye *ab*duction the *ipsi*lateral eye can neither abduct nor adduct. *one-and-a-half-syndrome*

Nuclei for the vagal and glossopharyngeal nerves can be found in the __

open (rostral) medulla **see diagram on slide 41 of Class 6 ppt

the main trunk of the facial nerve goes to the __ while other motor neurons in the nerve supply branches to the __

the main trunk of the facial nerve goes to the *middle ear* while other motor neurons in the nerve supply branches to the *facial muscles*

Which of the following cranial nerve(s) is (are) not located at the junction of pons-medulla? vestibulocochear trigeminal facial abducens

trigeminal