cranial nerves, brain stem reflexes and brainstem disorders Flashcards
CN 1
impairment
permanent loss
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
superior and inferior recti insert where and do what
superior and inferior oblique insert where and do what
recti: anteriorly, adducts
oblique: posteriorly, abducts
superior insertion-superior rectus and superior oblique rotate the eye
bottom insertion-inferior rectus and inferior oblique
superior-medially or inward torsion
inferior-laterally or outward torsion
lateral rectus
medial rectus
lateral-abduction
medial-adduction
Oculomotor nerve lesion
- ptosis-levator palpebrae superioris muscle-ipsilateral
- eye out-unopposed lateral rectus
- pupil large and unreactive to light directly or consensually
CN 4
location
ipsi or contra
defect
only nerve that exits the brainstem dorsally and decussates to innervate the contralateral superior oblique
lesion: Impairment of downward gaze
CN 6
ipsilateral rectus muscle-impairment of abduction of the affected eyeball
How is binocular diplopia resolved?
coving either eye
WHat are somethings that can cause diplopia?
3,4,6 leions
-brainstem or cerebellar lesions
What causes monocular diplopia?
looking with one eye alone
-optical system of an eye like dislocated lens or detached retina or psychiatric disorder
How can you tell nystagmus from lesions vs nystagmus from drug toxicity?
lesions-more prominent with certain eye movements
drug-symmetrical and present in all eye movements
Internuclear ophthalmoplegia (INO)
paralysis of extraocular muscles from a lesion between the nuclei involved with lateral gaze (3 and 6)
Gaze right
- 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
What is the most common cause of MLF lesions?
- multiple sclerosis in younger patients
- ischemic infarction in older patients
How does consensual response work in pupillary reflex?
- retinal ganglion cells project bilaterally to the pretectal area (superior colliculus)
- then project to the edinger westphal nucleus of 3
How does a left optic nerve lesion affect the pupil?
light shined onto left eye neither constrict
light shined on right eye both constrict
How does a right CN 3 lesion affect the pupil?
enlarged right pupil never constricts
yet left pupil constricts when light is shined in either eye
Relative afferent pupillary defect (RAPD)
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
argyll robertson pupils
light-near dissociation seen in neurosyphilis
-accommodate but don’t react to light
dorsal midbrain (parinaud’s) syndrome
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)
Horner’s syndrome
lesion disrupting the oculosympathetic pathway cuasing 1. miosis 2. anhidrosis 3. mild ptosis
Trigeminal nerve 3 divisions
- V-1 opthalmic
- V-2 maxillary
3 V-3 mandibular (should not include corner of jaw or neck)
V1 sensory impairment + ipsilateral involvment of 3,4,6 may occur from a lesion at what
superior orbital fissure
Trigeminal Neuralgia
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
Lower motor neuron lesion in trigeminal motor nerve
jaw deviating toward lesion
upper motor neuron lesion in trigeminal motor nerve one side
vs.
bilateral
one side: no deviation or severe weakness
bilateral: hyperreflexia jaw jerk
Each facial nerve innervates the ipsilateral facial muscles, what happens with a lower motor lesion?
severe paralysis of entire ipsilateral half of face
Ipsilateral face paralysis + impaired taste over 2/3 tongue
chorda tympani branch involved
ipsilateral face paralysis + sensitivity to sound(hyperacusis)
stapedius muscle denervation
ipsilateral face paralysis+hyperacusis+hearing impairments and tinnitus
involvment of CN8
-acoustic neuroma
Ipsilateral face paralysis ipsilateral weakness of lateral gaze
lesion at facial nucleus in pons
-involvment of adjacent PPRF and CN 6
What is a common syndrome that causes lesions in CN7?
bell’s palsy
lesion in upper motor neurons of 7
lower half of face controlled by only contralateral upper motor neurons
–>facial paralysis of lower part of the contralateral face, sparing the forehead
gag reflex
9
lower motor neuron of 10 innervates the palate what happens when there is a lesion
ipsilateral dropping or sagging of palatal arch
-uvula pointing to other (normal) side
lower motor neuron of vagus innervates larynx what happens when there is a lesion
hoarseness from ipsilateral paralysis of vocal cord muscles
CN 12 lower motor lesion lesion
weakens ipsilateral sterno and trap muscle
- weakness in turning head to the opp side
- decreased elevation of shrugging shoulder on same side
CN 12 lesion lower motor neuron
lick your wounds
deviate toward side of lesion
-atrophy and fasciculations and fibrillations
upper motor controlling 12 lesion
left frontal lobe ischemic infarct
right half of tongue weak
- turn toward opposite side of lesion
- but most people have bilateral innervation soooooo this doesn’t happen
medial midbrain syndrome (weber syndrome)
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
Lateral Medullary syndrome
PICA infarction or vertebral
- vestibular nuclei
- vomiting, vertigo, nystagmus - lateral spinothalamic tract
- decreased pain and temp sensation contralateral body - spinal trigeminal nucleus
- decreased pain and temp-ipsilateral face - nucleus ambiguus***
- dysphagia, hoarseness, decreased gag reflex - sympathetic fibers
- ipsilateral horner’s syndrome - inferior cerebellar peduncle- ataxia and dysmetria
VASST IC
