Cranial Nerve Disorders

Question 1

How many cranial nerves are there?

Answer 1

12 pairs

4 cr nerves above the pons-4 in the pons and 4 below.

Question 2

4 medial structures

Answer 2

1. motor nuclei 3/4/6/12
2. motor tract = pyramidal tract
3. MLF
4. medial lemnicus
   basilar and vertebral

Question 3

4 lateral structures

Answer 3

1-Symapthetics)
(2-spinothalamic)
(3- spinocerebellar)
(4- sensory nuc. Of cranial nerve V)

Post. Cerebral Art/Sup cerebellar Art/Anterior. Inferior cerebellar Art/ Post. Inferior cerebellar artery

Question 4

Cranial Nerve 1

Answer 4

origin= olfactory tracts

descends into nares through cribiform plate

Question 5

What is cranial nerve 1 associated with?

Answer 5

smell and most of taste
is easily damaged with trauma
will decrease with age

Question 6

Cranial Nerve 2

Answer 6

vision

uni or bilateral

Question 7

Unilateral issues with cranial nerve 2–> look for?

Answer 7

Unilateral ddx- refraction: test with pin hole
Media contact lens/cornea/eye lens /vitreous
Retinal/Macular: respects a horizontal meridian or + amsler grid which reviews the center 10 degrees of vision
Optic nerve –afferent pupillary defect (APD)=Marcus Gunn pupil/red desaturation/acuity loss
Functional
Amblyopia

Question 8

Bilateral loss with cranial nerve 2–> look for?

Answer 8

Bilateral loss is chiasmal/optic tract/lateral geniculate/optic radiation/occiput
Rules: Field defects are more congruous the more posterior
: visual acuity is spared in far posterior lesions
: vascular retinal lesions tend to show field defects top or bottom –respecting a horizontal meridian chiasmal and posterior lesions cause R/L defects respecting a vertical meridian

Question 9

Optic Neuritis (6)

Answer 9

“Pt sees nothing—Practitioner sees nothing”’
If at nerve head- disc edema (field defect+)
If retrobulbar-nl disc on exam (field defect +)
Can be painful- most are Fast onset hrs/day
18 % progress to MS
No etiology-immune mediated-treated with IV not oral steroids-usually unilateral-many resolve with no tx-
Atypical if :age >50,disc pallor at presentation, painless, slow progression over weeks, systemic symptoms (fever, malaise, wt loss etc.)

Question 10

Diplopia rules for cranial nerve 3-4-6

Answer 10

Diplopia study is best done with an eye model or picture of globe and muscles insertion
Head trauma can cause dysfunction of any of these nerves (3-4-6) and 6 is most common
Ischemia is most likely (microvascular) in older age groups and pain can be a big problem

Question 11

Cranial Nerve 3 anatomy

Answer 11

midbrain nucleus (Medial divides into 1/2) –Runs 4 ocular muscles and parasympathetics and levaltor palpebri

Question 12

Most common and most deadly for cranial nerve 3

Answer 12

Most common “Pupillary Sparing Diabetic Third”
Most deadly- PCOM (posterior communicating artery) aneurysm pressure “Blown pupil and the Lid is down”
Can be more painful ischemic than compressive
Given third nerve weakness the lateral rectus rules—Eye is Abducted

Question 13

what are you thinking with Cranial nerve 4 dysfunction?

Answer 13

Vertical diplopia – likely from a 4th nerve ischemia or trauma—tumor less common

Beware of myasthenia which can present with dysfunction of one muscle however!
Thyroid disease also can present with one muscle defective early-can mimic 3/4/6

Question 14

Cranial nerve 5 (3)

Answer 14

Lateral rectus function
Long course lends to problems from trauma and tumors and intracranial pressure
Common pressure issues with #6 happen with Idiopathic intracranial hypertension- bending over and getting up/low csf pressure arising from supine

Question 15

Cranial nerve 5 common disturbance

Answer 15

1. Trigeminal neuralgia- unilateral in most-idiopathic in most- trigger points common-any division or all-
2. zoster V1 is most intense

Question 16

Treatment for trigeminal neuralgia

Answer 16

Tx gamma knife and Jenetta proceedure-lancinating pain- refractory to narcotics
rx anticonvulsants

Question 17

Treatment for zoster

Answer 17

acyclovir

Question 18

Cranial Nerve 7

Answer 18

Facial motor function
Most common disorder Bell’s Palsy
Onset facial numbness common
Abrupt facial weakness incl forehead
treat with steroids

Question 19

CPA tumor

Answer 19

freq meningioma /epidermoid/acoustic
Best physical sign is loss of corneal reflex V-1
loss of hearing– crn 8

Question 20

Cranial Nerve 8

Answer 20

Auditory and starting in Middle ear
Hearing/tinnitus from cochlea
Balance from Semicircular canals

Question 21

Cranial nerve 9 & 10

Answer 21

Motor and Sensory to throat

Glossopharyngeal neuralgia

Question 22

Cranial nerve 11

Answer 22

Runs the Trapezius
Unilateral defect with neck surgery/trauma (Hod carrier )
uncommon

Question 23

Cranial nerve 12

Answer 23

Tongue motor
Sensory is CN V3
Genioglosssus protrudes the tongue
Atrophy occurs with motor neuron disease
deviates to the side of the stroke/lesions

Question 24

CN 1- Olfactory 3 MC causes

Answer 24

Anosmia – Loss of sense of smell
Most common causes:
Trauma (shearing of “bulb”)
Olfactory groove Meningioma - surgical
Neurodegenerative Disease

Question 25

CN 1- Olfactory Clinical Presentation

Answer 25

Usually presents as loss of taste | Loss of smell picked up on examination

Question 26

CN 1- Olfactory- Neurodegenerative Disease

Answer 26

Alzheimer’s & Parkinson’s – early symptom / sign – loss of smell -? Predictor of impending disease?? Insufficient data to use this as a reliable predictor Tx: address underlying cause if possible.

Question 27

CN II- Optic Nerve= Optic Neuritis clinical presentation (6)

Answer 27

Sudden onset of ocular pain (severe) Followed by decreased central vision or central vision loss Most common women 25 – 45 yrs. old Idiopathic in nature or demyelinating disease Presence of a RAPD (Relative Afferent Pupillary Defect) – Marcus Gunn Pupil Usually resolves spontaneously

Question 28

Optic Neuritis treatment

Answer 28

Steroids sometimes used W/U Pt for demyelinating disease (MS) MRI looking for white matter lesions 10 – 20% chance of occurring again or in other eye

Question 29

2 Types of Ischemic optic neuropathy

Answer 29

Arteritic – secondary to Temporal Arteritis Non-arteritic – secondary to cerebrovascular disease

Question 30

Vitamin B12 Deficiency (4)

Answer 30

Characterized by cognitive changes Change in level of consciousness Inattention, confusion, somnolence, apathy Ocular finding is BILATERAL optic neuropathy – loss of central vision – greater loss of color than black and white vision.

Question 31

Ischemic optic neuropathy- Arteritic

Answer 31

Temporal Arteritis / Vasculitis Complication of DM, HTN, or increased cholesterol Causes visual loss – less common

Question 32

Ischemic optic neuropathy- NON Arteritic

Answer 32

``` Usually painless and temporary visual loss RAPD present Disc is usually hyperemic (reddened) Flame hemorrhages may be present Symptoms usually improve spontaneously ```

Question 33

What does Horners syndrome result from

Answer 33

Results from loss of sympathetic innervation of the eye Classic symptoms: ptosis, miosis (small pupil), anhidrosis (lack of sweating) on ipsilateral face Many different causes possible Often results in anisocoria

Question 34

How to diagnose/ treat horners syndrome?

Answer 34

MRI usually helpful Treat the causal lesion if possible

Question 35

3rd occular nerve palsy

Answer 35

controls pupil constriction, superior and inferior gaze and medial (nasal) gaze. III Nerve palsy = dilated non-reactive pupil

Question 36

6th occular nerve palsy

Answer 36

controls lateral (temporal) gaze

Question 37

4th occular nerve palsy

Answer 37

hard to see on exam (pts will note diplopia when looking downward)

Question 38

Internuclear Ophthalmoplegia

Answer 38

Often associated w/MS Localizes lesion to the Medial Longitudinal Fasciculus (MLF) Pt has WEAK adduction of affected eye (cannot gaze nasally) with abduction nystagmus of the contralateral eye pt can converge****

Question 39

Trigeminal Neuralgia

Answer 39

Sudden, severe, unilateral lancinating facial pain Most common in V2 and V3 branches (cheek / chin) Pain can be spontaneous or triggered (so called trigger zones) Touching the face, washing, shaving, chewing, talking, even wind/breeze on the face can trigger Common after 50

Question 40

Medical Treatment for Trigeminal Neuralgia

Answer 40

aimed at controlling attacks with a minimum of side effects Anti-epileptic meds w/analgesic properties Carbamazepine was first line – newer agents used now like: Gabapentin, Baclofen, Na Valproate, Oxcarbazepine, Topiramate

Question 41

Surgical Treatment for Trigeminal Neuralgia

Answer 41

initiated only if medical treatments fail Gamma Knife Radiosurgery (GKRS) – produces controlled injury of the trigeminal nerve (knock out pain fibers but preserve sensation) Percutaneous procedures i.e., thermal rhizotomy, balloon compression of the nerve

Question 42

2 common facial nerve problems

Answer 42

bells palsy | ramsey hunt syndrome

Question 43

Bells palsy

Answer 43

Unilateral facial weakness Affects upper and lower face Facial weakness of lower face = central facial weakness (typical of stroke) Facial weakness of upper and lower is peripheral weakness seen in BP – can’t close eye Facial sensation (CN V) is spared

Question 44

Treatment and Diagnose for bells palsy

Answer 44

Diagnosis: Hx & PE (some have day or two of auricular pain prior to BP) Tx: corticosteroids, anti-virals (i.e. acyclovir)

Question 45

Prognosis of bells palsy

Answer 45

majority of pts have full resolution but could take weeks or months – some have a degree of residual weakness

Question 46

Ramsey Hunt Syndrome

Answer 46

RHS is caused by Varicella Zoster virus of the geniculate ganglion – results in Facial Nerve palsy Geniculate ganglion is neurons in the facial nerve found in the facial canal. Sensory fibers of the facial nerve so RHS frequently affects taste

Question 47

Ramsey Hunt Syndrome Treatment

Answer 47

Corticosteroids Acyclovir for certain w/RHS Most pts recover fully but some residual symptoms can remain

Question 48

2 component of the acoustic nerve

Answer 48

auditory nerve | vestibular nerve

Question 49

Acoustic Neuroma/ Vestibular Schwannoma

Answer 49

Benign tumor of the vestibular portion of the Acoustic (VIIIth nerve) Increased incidence in pts with neurofibromatosis

Question 50

presentation of acoustic neuroma

Answer 50

ipsilateral hearing loss, vertigo and tinnitus Because of proximity of CN VII many pts will have an ipsilateral facial weakness MRI can localize tumor to the CP angle in the posterior fossa of the brain

Question 51

treatment of acoustic neuroma

Answer 51

surgery is the only significant Tx approach | Neurosurgery and ENT team to remove tumor from cerebello-pontine angle