Neurology Cranial Nerves

What sensory information does the facial nerve receive?

-*Ant 2/3 tongue (taste)* -Skin in ear canal (touch, px, heat, cold)

Glossopharyngeal (CN IX) -Responsible for what?

CN responsible for taste, swallowing, proprioception, baroreceptors, chemoreceptors, saliva secretion and external ear sensation.

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Condition that can occur with Bell's Palsy where eyes water due to salivation stimulus (crossed stimulation):

Crocodile Tears

-MM attaches to little bones in ear that amplify sound, dampens excessively loud sound to protect the ear bones

Stapedius "prevents a stampede of noise"

What foramen does the Facial nerve travel through?

Stylomastoid

Which muscle does the Trochlear nerve innervate?

Superior Oblique only

Which foramen does the Abducens pass through?

Superior Orbital Fissure

Is CN III - Oculomotor an autonomic/parasympathetic nerve?

Yes

is CN IX autonomic?

Yes

Olfactory Nerve -CN number? -What type of nerve (i.e. sensory or motor) -Contains what?

(CN I) -entirely sensory -contain axons that conduct nerve impulses for sense of smell

Vestibulocochlear -CN#? -# branches? -What kind of impulses does it carry?

(CN VIII) CN w/ 2 branches carrying impulses for hearing & equilibrium.

Injury to Glossopharyngeal nerve can result in:

*-dysphagia* (difficulty swallowing) *-aptyalism* (absent saliva secretion) -loss of sensation in throat *-ageusia* (loss of taste) *Like trigeminal neuralgia but in the back of the mouth and the throat*

What part of the tongue is the Glossopharyngeal nerve responsible for? is it taste?

*-posterior* 1/3 tongue -yes taste

CN's to do with eye movement but not vision

*3,4,6 make your eyes do tricks* (Oculomotor, Trochlear, Abducens)

What percentage of the ANS is innervated by the Vagus nerve? What does the Vagus nerve innervate?

*80%* Lungs, Heart, Glands of GI, Smooth mm of Respiratory, Esophagus, Stomach, Gallbladder, Small Intestine, Most of Large Intestine

What is the *most important function* of the Vagus nerve?

*Autonomic function* (Parasympathetic)

Which CNs control each extrinsic eye muscle?

*CN IV - Trochlear:* Superior Oblique only (makes you look down and out "like you're on trochlear street") *CN VI - Abducens:* Lateral Rectus only (i.e. it ABDUCTS the eye) *CN III - Oculomotor:* All the rest (Superior Rectus, Inferior Rectus, Medial Rectus, Inferior Oblique)

What does the autonomic branch of the facial nerve innervate?

*Glands* -lacrimal gland -palatine gland -submandibular gland -sublingual glands

What gland does the facial nerve travel through but not innervate?

*Parotid Gland* -facial nerve does not innervate the parotid gland but branches out as it travels through it. -troubles with parotid gland can cause issues with facial nerve. -tapping parotid gland is a test that can elicit symptoms (Chvostek's sign)

What does the Autonomic branch of the Glossopharyngeal innervate?

*Parotid* Gland

How to remember if cranial nerve function is Sensory, Motor or Both:

*S S M M B M B S B B M M* *S*ome *S*ay *M*oney *M*atters, *B*ut *M*y *B*rother *S*ays *B*ig *B*oobs *M*atter *M*ore

Where do the motor axons of the Accessory nerve originate?

*Spinal Cord* (C1-C5)

What muscle does the Glossopharyngeal nerve innervate?

*Stylopharyngeus* mm (elevates pharynx & larynx)

What is another name for Trigeminal Neuralgia?

*Tic Douloureux* (chim chimney chim chim cha roo)

Which CN has 3 branches? What are they?

*Trigeminal: CN V* 1. Opthalmic (V1) 2, Maxillary (V2) 3. Mandibular (V3) (this is the SENSORY portion)

Why does the heart speed up with damage to the Vagus nerve?

*Vagus* stimulates *Parasympathetic*, so loss of signal causes SNS to speed up the heart

which branch of the CN VIII Vestibulocochlear goes to both Pons and Medulla?

*Vestibular -> Both* (Cochlear -> Medulla only)

What are the 3 layers of the neural tube? what do they form?

*outer/marginal layer cells* = white matter of nervous system *middle/mantle layer cells* = grey matter *inner/ependymal layer cells* = lining of central canal (spinal cord) and ventricles of brain

Damage to the Oculomotor nerve can result in:

*strabismus* (condition in which both eyes do not fix on same object, one or both eyes may turn inward or outward) *ptosis* (drooping of upper eyelid - levator palpebrae fails) *dilation of pupil* (circular mm fails) *mvmt of eyeball downward + outward* on damaged side *loss of accommodation* for near vision (ciliary mm fails) *diplopia* (double vision)

Damage to the trochlear nerve can result in:

*strabismus* (unable to fix eyes on same object) *diplopia* (double vision)

Damage to cochlear branch of vestibulocochlear nerve will result in:

*• tinnitus* (ringing in ears) *• deafness*

Damage to vestibular branch of vestibulocochlear nerve will result in:

*• vertigo*: a subjective feeling that one's own body or the environment is rotating *• ataxia*: muscular incoordination *• nystagmus: *involuntary rapid movement of the eyeball

What do autonomic nerves control (generally)?

Smooth muscle, heart muscles, glands.

-do contain some sensory neurons that bring back signals from muscle spindles in muscles they control

motor nerves

Symptoms of Trigeminal Neuralgia:

- sudden pxful attacks - px often occurs in clusters *- unilateral* - along one or more distributions of the nerve

Where is the Olfactory sensory nerve located?

- superior part of nasal cavity - inferior surface of the cribriform plate *(ethmoid bone)* - along the superior nasal concha

What can cause Trigeminal Neuralgia?

- local compression - *herpes zoster*, vascular lesions, tumours - demyelinating conditions w/ subsequent scarring (MS) - idiopathic

path of the motor branch of vagus nerve:

- medulla > jugular foramen > mm of pharynx, larynx,& soft palate (swallowing, vocalization, coughing)

Cranial Nerves -What do the numbers indicate? -What do the names indicate?

- numbers indicate the order *(anterior => posterior)* that nerves arise from the brain - names indicate the nerve's distribution or function

Trigeminal Neuralgia -What does it feel like and how long do the sx last? -What causes it? -Trigger zones? -Triggers?

- sharp cutting, intense, *"lightning bolt-like"* px that lasts for a few seconds to a minute - is caused by anything that presses on the trigeminal nerve or its branches - Trigger zone may be lips, face, tongue (touch, temp, facial mvt) - any mechanical stimulation, chewing, smiling, a breeze felt on the cheek can trigger an attack

Sensory branch of the Vagus nerve receives from:

- skin of external ear for touch, pain , heat and cold *- a few taste buds in epiglottis and pharynx* - proprioceptors in mm of neck and throat - *baroreceptors* in carotid *sinus* & *chemoreceptors* in carotid & aortic *bodies* - mainly from visceral sensory receptors in most organs of thoracic & abdominal cavities that convey sensations *(ie hunger, fullness, discomfort)*

Damage to Abducens nerve can result in:

-*cross eyed* (affected eyeball only; can't move laterally beyond midpoint + eyeball is usually directed medially) -*strabismus* (cannot fix on object) -*diplopia* (double vision)

Cranial Nerves - facts

-12 pairs -Named cranial because they pass through various foramina in bones of the cranium & arise from brain inside the cranial cavity -Like spinal nerves, they are part of the peripheral nervous system (PNS)

Optic -CN #? -Sensory or motor? -Contains what?

-CN II -entirely sensory -contains axons that conduct nerve impulses for vision

-Which extrinsic eye muscle nerve is the only one to arise from the posterior brain stem?

-CN IV: Trochlear

What muscles does the Facial nerve innervate?

-Facial expression mm -Stylohyoid mm -Posterior Digastric mm *-Stapedius mm*

Glossopharyngeal neuralgia -What is it siminlar to? -Sx? -What is it due to? -How common? M vs F? Age? -What stimulates an attack? -How long does pain last and where does it begin and radiate to?

-Like Trigeminal Neuralgia but pain only in the throat (i.e. paroxysmal attacks of unilateral brief, excruciating pain) -recurrent attacks of severe pain in the CN IX nerve distribution (posterior pharynx, tonsils, back of tongue, middle ear) -from nerve compression -rare, more common in men, usually after 40 -occurs spontaneously or are precipitated by certain movements (eg: chewing, swallowing, talking, sneezing). Also swallowing or touching tonsils with an applicator triggers pain -pain lasts seconds to a few minutes, usually begins in tonsil area or at base of tongue and may radiate to ipsilateral ear.

What are 2 common neural tube defects? What typically causes them?

-Spina Bifida & Anencephaly -caused by deficiency in folic acid

Anosmia

-a loss of sense of smell from infections of nasal mucosa, head injuries, lesions along olfactory pathway, meningitis, smoking, cocaine use

Development of the nervous system: -begins in ___________ week of gestation -Starts with a ___________ of the _____________ called the __________ ____________. -______________ ________________ folds inward and forms a longitudinal groove called the _______________ ________________ -Raised edges of the _________________ __________________ are called ____________ _______________ -As the whole thing grows it forms a tube, now called the ________________ _________________

-begins in the *3rd week of gestation* -starts with a thickening of the ectoderm called the *neural plate* -neural plate folds inward + forms a longitudinal groove, called the *neural groove* -raised edges of neural plate are called *neural folds* -as the whole thing grows it forms a tube, *now called the neural tube*

Anopia

-blindness due to a defect or loss of 1 or 2 eyes (from fractures in orbit, brain lesions, damage along pathway, disease of the nervous system, pituitary gland tumours, cerebral aneurysm)

What is the difference b/w a stroke and bell's palsy?

-can open and close your eye with stroke, can control forehead and eyes -Bell's Palsy affects the entire side of face

Bell's Palsy

-condition involving the facial nerve -results in paralysis of the mm of facial expression on the same side as the lesion -is one of the most common neurological conditions -it affects at least 25 people out of 100,000 each year

Bipolar Cell layer

-connects rods and cones with ganglion cells

Photoreceptors

-deepest layer -initiates visual signals and convert them to nerve impulses

Prognosis of Bell's Palsy:

-if only segmental demyelination (as w/ compression / neuropraxia), recovery is usually in 2-8 weeks -if Wallerian degeneration = poorer prognosis

Hyperosmia

-increased sense of smell

Ganglion Cell layer

-layer of retinal interneurons farthest from the photoreceptors, which contains cells and gives rise to the optic nerve

What foramen does the Trigeminal nerve pass through?

-ophthalmic: *superior orbital fissure* -maxillary: *foramen rotundum* -mandibular: *foramen ovale*

What does the motor branch of the Vagus nerve innervate?

-pharynx, larynx, soft palate -swallowing -vocalization -coughing

Rods -What do they allow us to do? -What kind of vision? -Where are they concentrated? -How numerous are they compared to cones?

-photoreceptor allows us to see in dim light -no colour (black/white/grey) -low acuity -concentrated in periphery -greater number of the 2 photoreceptors

Cones -What is it stimulated by? -What kind of vision? -Clarity? -Where are the concentrated? -How numerous compared to rods?

-photoreceptor stimulated in bright light -colour vision -high acuity -concentrated in the center of retina (macula) -less in number of the 2 photoreceptors

Hyposmia

-reduced ability to smell -affect half of those over 65 and 75% of those over 80 -can also be caused by neurological changes

What are the extrinsic muscles of the eye? What are their movements?

-superior rectus (make eyes look up) -inferior rectus (make eyes look down) -lateral rectus (make eyes look lateral/out) -medial rectus (make eyes look medial/in) -superior oblique *(make eyes look down & out)* -inferior oblique* (make eyes look up & out)* (superior and inferior oblique are seemingly opposite due to a loop attachment) These are the only muscles that attach to the white (or sclera) of the eye.

Bell's palsy symptoms

-unilateral weakness followed by flaccid paralysis of muscles of facial expression -Onset of symptoms from weakness to flaccid paralysis is quite rapid -sagging of face and eyelid w/ possible pulling toward unaffected side

What are the 2 types of photoreceptor?

1. Cones 2. Rods

What muscles are controlled by the Oculomotor nerve (7)?

1. Superior Rectus 2. Inferior Rectus 3. Medial Rectus 4. Inferior Oblique *5. levator palpebrae superioris* *Autonomic:* 6. Ciliary mm of lens 7. Circular mm of iris

What are the 3 layers of retinal neurons?

1. photoreceptors (deep) 2. bipolar cell layer (middle) 3. ganglion cell layer (superficial)

Which CNs function autonomically (parasympathetically)?

10, 9, 7 & 3 10, 9, 7, 3 function autonomically

What percentage of axons cross at the optic chiasm?

50%

Motor nerve that innervates the tongue:

CN XII Hypoglossal Nerve

What does CN VI innervate?

Abducens: Lateral Rectus only

Is the Facial nerve sensory, motor and/or autonomic?

All

Is the Vagus nerve Motor, Sensory or Autonomic?

All 3

Where are Baroreceptors and Chemoreceptors located?

Baroreceptors => Carotid *Sinus* Chemoreceptors =>Carotid *Body* & *Aortic Body*

Is the Trigeminal nerve motor or sensory?

Both

is CN IX motor or sensory?

Both

Parotid Gland

C=Parotid Gland The facial nerve does not innervate the parotid gland, but it does go through the parotid gland and branches to innervate muscles of face.

Which is the *smallest CN*?

CN IV - Trochlear

Ophthalmic

CN V1 Sensory from skin over upper lid, cornea, lacrimal glands, upper nasal cavity, side of nose, forehead, anterior half of scalp GOES TO Superior Orbital Fissure GOES TO Ophtalmic Branch

Maxillary

CN V2 Sensory from mucosa of nose, palate, part of pharynx, upper teeth, upper lip, lower eyeball GOES TO Foramen rotundum GOES TO Maxillary Branch GOES TO Trigeminal Ganglion GOES TO Pons

Mandibular

CN V3 Sensory from anterior 2/3 of tongue (not taste), cheek and its mucosa, lower teeth, skin over mandible, side of head anterior to ear, mucosa of floor of mouth GOES TO Foramen Ovale GOES TO Mandibular branch

Cranial nerve that is motor only but must travel into the brain before travelling to its innervated tissue:

CN XI Accessory Nerve

Cranial nerve VII:

Facial nerve

What foramen does the Accessory nerve use?

Foramen Magnum (into skull) Jugular Foramen (out of skull)

What 2 CNs have baroreceptors and chemoreceptors?

Glossopharyngeal Vagus

which nerves travel through the jugular foramen?

Glossopharyngeal Vagus

Where does the sensory branch of the Facial nerve terminate?

Gustatory Area (43) Temporal lobe

CN III

Has both a motor and autonomic component. The extrinsic eye muscles it controls are MOTOR and the ciliary is the AUTONOMIC component

Where does the Olfactory CN I synapse through if not the thalamus?

Hypothalamus

How to remember the cranial nerves:

I Olfactory nerve II Optic nerve III Oculomotor nerve IV Trochlear nerve V Trigeminal nerve VI Abducens nerve VII Facial nerve VIII Vestibulocochlear nerve IX Glossopharyngeal nerve X Vagus nerve XI Accesory nerve XII Hypoglossal nerve Oh Oh Oh To Touch A Female Vagina Gives Vagus A Hardon

Bell's Palsy Cause - conceptual

It's thought that as the nerve travels down the long, narrow canal in the temporal bone, even minor swelling could cause a compression of the facial nerve which would result in a lesion.

What foramen does the Glossopharyngeal (CN IX) travel through?

Jugular Foramen

Which foramen does the Vagus nerve travel through?

Jugular foramen (same as Glossopharyngeal)

what are crocodile tears (bonus question)

Lacrimation instead of salivation due to nerve injury of Facial nerve

Autonomic path of the vagus nerve

Medulla --> jugular foramen --> smooth muscle of lungs, cardiac muscle, glands of the GI tract, smooth mm of respiratory passageways, esophagus, stomach, gallbladder, small intestine, most of large intestine

Where is the nucleus found for the Oculomotor nerve?

Midbrain

Is CN III - Oculomotor a sensory or motor nerve?

Motor

their cell bodies are in nuclei within the brain

Motor cranial nerves

Is the Abducens nerve a Motor or Sensory nerve?

Motor only

Is the Trochlear nerve Motor or Sensory?

Motor only

What does the Trigeminal nerve motor branch innervate (6)?

Muscles of Mastication (mainly chewing) -Temporalis -Masseter -Medial Pterygoid -Lateral Pterygoid (+ Mylohyoid & Digastric)

Path of Accessory nerve:

NOTE: it starts in the spinal cord, goes up into skull, then comes back out again.

mass of tissue b/w the neural tube & skin ectoderm

Neural crest

Does the Trigeminal nerve send taste sensation from anterior 2/3 tongue to the brain?

No

Is CN VIII autonomic?

No

Is the Abducens nerve an autonomic nerve?

No

Is the Trigeminal nerve an autonomic nerve?

No

Is the Trochlear nerve an autonomic nerve?

No

Causes of Bell's Palsy include:

Not fully understood, but may be: *nerve damage from:* -viral infection (shingles) -bacterial infection (lyme's disease) *compression from edema w/:*pregnancy, middle ear infection, diabetes, hypertension, *hypothyroidism*, *leprosy* *conditions involving the parotid gland* *trauma* *exposure to chill or draft*

What is the only sensory nerve that does not synapse with cerebral cortex through the *thalamus*?

Olfactory (CN I)

What part of the nervous system is the Vagus nerve responsible for; CNS or PNS?

PNS (peripheral nervous system)

Injury of the Accessory nerve would result in what?

Paralysis to SCM & Trapezius

What is under the optic chiasm? (sam bonus question)

Pituitary gland. A pituitary gland tumor would press on the optic chiasm and affect vision.

What part of the brain does the Abducens nerve arise from?

Pons

What part of the brain does the Trigeminal nerve arise from?

Pons

CN XI Accessory Nerve innervates what tissue?

SCM and Trapezius mm:

2 main types of nerves:

Sensory Nerves Motor Nerves

most of their cell bodies are in ganglia outside the brain

Sensory cranial nerves

Is CN VIII sensory or motor?

Sensory only

Accommodation

The ciliary mm functions to flatten or make more spherical, the lens to be able to see near vision, closer than 20 feet. NOTE: when the object is more than 20 feet away, there is no change needed in the lens to be able to see clearly (in a healthy eye).

What does the neural crest form into?

The mass of tissue between the neural tube and skin of the ectoderm becomes : -posterior (dorsal) root ganglia of spinal nerves - spinal nerves - ganglia of cranial nerves - ganglia of autonomic nervous system - adrenal medulla - meninges

General direction of cranial nerves

The sensory portion always starts outside and goes in; the motor always starts in and goes out.

What is the *largest* of the 12 Cranial Nerves?

Trigeminal

what nerve is brain freeze (bonus question)

Trigeminal

T/F, the Oculomotor nerve controls both extrinsic and intrinsic eye muscles?

True

Which branch of the Trigeminal nerve is usually affected by Trigeminal Neuralgia?

Usually *V2* or *V2* & *V3* (V1 = Opthalmic, V2 = Maxillary, V3 = Mandibular)

what is the Vagus nerve named after? (bonus question)

Vagrant or wanderer

*80% of Parasympathetic signals* travel along this nerve:

Vagus (CN X)

What are the 2 branches of the Vestibulocochlear nerve called?

Vestibular Branch (equilibrium) Cochlear Branch (hearing)

In addition to mm paralysis (Bell's palsy), what happens if sensory + autonomic branches of Facial nerve are injured/lesion?

if sensory + autonomic affected can't control lacrimation, usually decrease in salivation, can't taste on anterior 2/3 of tongue, heightened sensitivity of hearing (stapedius paralysis)

3,4,6 all go through what foramen?

superior orbital fissure (a fissure in the eye socket of the skull)

How can you damage the vestibulocochlear nerve?

trauma, lesions, middle ear infections

Injury to the Hypoglossal nerve will result in:

• difficulty chewing • dysarthria - *Slurred speech (dys-aaaaarrr-thria)* • dysphagia - difficulty swallowing • the tongue, when protruded, curls toward the affected side and that side atrophies

Injury to the Vagus nerve can result in:

• vagal paralysis (no information from organs) • dysphagia (difficulty swallowing) • tachycardia (rapid heart rate)