cranial nerves, brain stem reflexes and brainstem disorders

Question 1

CN 1
impairment
permanent loss

Answer 1

impairment: upper respiratory tract infection
permanent:
- head trauma-branches are torn when they pass through the cribriform plate
- tumor near olfactory lobe at the base of skull-such as meningioma

Question 2

superior and inferior recti insert where and do what

superior and inferior oblique insert where and do what

Answer 2

recti: anteriorly, adducts
oblique: posteriorly, abducts

Question 3

superior insertion-superior rectus and superior oblique rotate the eye

bottom insertion-inferior rectus and inferior oblique

Answer 3

superior-medially or inward torsion

inferior-laterally or outward torsion

Question 4

lateral rectus

medial rectus

Answer 4

lateral-abduction

medial-adduction

Question 5

Oculomotor nerve lesion

Answer 5

1. ptosis-levator palpebrae superioris muscle-ipsilateral
2. eye out-unopposed lateral rectus
3. pupil large and unreactive to light directly or consensually

Question 6

CN 4
location
ipsi or contra
defect

Answer 6

only nerve that exits the brainstem dorsally and decussates to innervate the contralateral superior oblique

lesion: Impairment of downward gaze

Question 7

CN 6

Answer 7

ipsilateral rectus muscle-impairment of abduction of the affected eyeball

Question 8

How is binocular diplopia resolved?

Answer 8

coving either eye

Question 9

WHat are somethings that can cause diplopia?

Answer 9

3,4,6 leions

-brainstem or cerebellar lesions

Question 10

What causes monocular diplopia?

Answer 10

looking with one eye alone

-optical system of an eye like dislocated lens or detached retina or psychiatric disorder

Question 11

How can you tell nystagmus from lesions vs nystagmus from drug toxicity?

Answer 11

lesions-more prominent with certain eye movements

drug-symmetrical and present in all eye movements

Question 12

Internuclear ophthalmoplegia (INO)

Answer 12

paralysis of extraocular muscles from a lesion between the nuclei involved with lateral gaze (3 and 6)

Question 13

Gaze right

Answer 13

1. right PPRF must activate
   a. right abducens nucleus in the pons
   b. left oculomotor nucleus in the midbrain

MLF leaves the right PPRF decussates early and rises to join the left oculomotor nucleus

–>lesion along the main left-sided course of the MLF here en route from pons to midbrain produces paralysis of adduction of left eye with nystagmus of right eye

Question 14

What is the most common cause of MLF lesions?

Answer 14

• multiple sclerosis in younger patients

- ischemic infarction in older patients

Question 15

How does consensual response work in pupillary reflex?

Answer 15

1. retinal ganglion cells project bilaterally to the pretectal area (superior colliculus)
2. then project to the edinger westphal nucleus of 3

Question 16

How does a left optic nerve lesion affect the pupil?

Answer 16

light shined onto left eye neither constrict

light shined on right eye both constrict

Question 17

How does a right CN 3 lesion affect the pupil?

Answer 17

enlarged right pupil never constricts

yet left pupil constricts when light is shined in either eye

Question 18

Relative afferent pupillary defect (RAPD)

Answer 18

partial optic nerve or retinal lesion

swinging plash light test-dilation occurs because of relatively reduced afferent input into the affected eye
-light stimulus produces direct and consensual response but to a lesser degree when the affected eye is stimulated

Question 19

argyll robertson pupils

Answer 19

light-near dissociation seen in neurosyphilis

-accommodate but don’t react to light

Question 20

dorsal midbrain (parinaud’s) syndrome

Answer 20

pineal tumor compressing the dorsal midbrain but may also occur from ischemic infarction
—>impairment of upward gaze and light-near dissociation of pupils
(MESSED UP 3, down and out and argyll robert pupil)

Question 21

Horner’s syndrome

Answer 21

lesion disrupting the oculosympathetic pathway
cuasing
1. miosis 
2. anhidrosis
3. mild ptosis

Question 22

Trigeminal nerve 3 divisions

Answer 22

1. V-1 opthalmic
2. V-2 maxillary
   3 V-3 mandibular (should not include corner of jaw or neck)

Question 23

V1 sensory impairment + ipsilateral involvment of 3,4,6 may occur from a lesion at what

Answer 23

superior orbital fissure

Question 24

Trigeminal Neuralgia

Answer 24

irritation or inflammation of the trigeminal nerve sensory branches which short circuits or misfires
“electrical shocks” usually V2 or V3

usual cause:

younger: MS lesion of trigeminal nerve entry region into the pons
older: trigeminal nerve branch is often compressed by a tortuous or kinked vessel

Question 25

Lower motor neuron lesion in trigeminal motor nerve

Answer 25

jaw deviating toward lesion

Question 26

upper motor neuron lesion in trigeminal motor nerve one side
vs.
bilateral

Answer 26

one side: no deviation or severe weakness

bilateral: hyperreflexia jaw jerk

Question 27

Each facial nerve innervates the ipsilateral facial muscles, what happens with a lower motor lesion?

Answer 27

severe paralysis of entire ipsilateral half of face

Question 28

Ipsilateral face paralysis + impaired taste over 2/3 tongue

Answer 28

chorda tympani branch involved

Question 29

ipsilateral face paralysis + sensitivity to sound(hyperacusis)

Answer 29

stapedius muscle denervation

Question 30

ipsilateral face paralysis+hyperacusis+hearing impairments and tinnitus

Answer 30

involvment of CN8

-acoustic neuroma

Question 31

Ipsilateral face paralysis ipsilateral weakness of lateral gaze

Answer 31

lesion at facial nucleus in pons

-involvment of adjacent PPRF and CN 6

Question 32

What is a common syndrome that causes lesions in CN7?

Answer 32

bell’s palsy

Question 33

lesion in upper motor neurons of 7

Answer 33

lower half of face controlled by only contralateral upper motor neurons
–>facial paralysis of lower part of the contralateral face, sparing the forehead

Question 34

gag reflex

Answer 34

9

Question 35

lower motor neuron of 10 innervates the palate what happens when there is a lesion

Answer 35

ipsilateral dropping or sagging of palatal arch

-uvula pointing to other (normal) side

Question 36

lower motor neuron of vagus innervates larynx what happens when there is a lesion

Answer 36

hoarseness from ipsilateral paralysis of vocal cord muscles

Question 37

CN 12 lower motor lesion lesion

Answer 37

weakens ipsilateral sterno and trap muscle

• weakness in turning head to the opp side
• decreased elevation of shrugging shoulder on same side

Question 38

CN 12 lesion lower motor neuron

Answer 38

lick your wounds
deviate toward side of lesion
-atrophy and fasciculations and fibrillations

Question 39

upper motor controlling 12 lesion

left frontal lobe ischemic infarct

Answer 39

right half of tongue weak

• turn toward opposite side of lesion
• but most people have bilateral innervation soooooo this doesn’t happen

Question 40

medial midbrain syndrome (weber syndrome)

Answer 40

Posterior cerebral artery infarction
CN3 and cerebral peduncle (corticospinal and corticobulbar tracts)
1. ipsilateral oculomotor lesion
2. upper motor neuron weakness of contralateral face and limbs

Question 41

Lateral Medullary syndrome

Answer 41

PICA infarction or vertebral

1. vestibular nuclei
   - vomiting, vertigo, nystagmus
2. lateral spinothalamic tract
   - decreased pain and temp sensation contralateral body
3. spinal trigeminal nucleus
   - decreased pain and temp-ipsilateral face
4. nucleus ambiguus***
   - dysphagia, hoarseness, decreased gag reflex
5. sympathetic fibers
   - ipsilateral horner’s syndrome
6. inferior cerebellar peduncle- ataxia and dysmetria

VASST IC