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cranial nerves - CNS or PNS?
- PNS
- they transmit impulses to and from the CNS
- sensory, motor, and reflex (autonomic) functions
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locations for cranial nerve lesions/abnormalities
- anywhere along the route:
- nerve,
- nucleus,
- pathways t/from cortex, diencephalon, cerebellum, brainstem,
- receptor (muscle, reflex, etc)
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you have to examine at impairment, functional limitation, and disability level for cranial verve lesions. For example, give issues in each of those three categories for a lesion to the vestibulocochlear nerve
- impairment: nystagmus and vertigo
- functional lim: disequilibrium
- disability: can't work
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CN I
- olfactory nerve
- solely afferent impulses for smell
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tsense of smell is the only sensory modality with...?
direct access to the cerebral cortex w/o going thru the thalamus
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olfactory tracts project mainly to the...?
uncus of the temporal lobes
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projections from the olfactory nerve to the __ suggests role in memory
- hippocampus - this is involved in memory
- pt's w weak smell do emotional blunting (due to limbic system) and have poorer memory)
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3 types of pathology that'll hit CN I
- classical pathology: olfactory groove meningioma
- basal skull fractures: can be uni or bilat
- part of a larger pathology:
note - injury to CN I isn't profoundly disabling but can affect QOL
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how to test CN I
- use non-noxious odors (though noxious are ok for sensory stim) and see if pt can detect it (detection is more important than identification)
- test unilaterally and bilaterally
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anosmia
- loss of smell uni or bilat
- can be a sudden loss due to infarct/trauma
- or a gradual loss due to tumor
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olfactory hallucinations can be signs of...?
a seizure coming on, or related to a limbic system lesion (not a cranial nerve lesion)
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CN II, and it's path
- optic nerve
- arises from retina
- pass thru optic canals
- converge at optic chiasm and do the half trade there
- continue to thalamus
- synapse there
- from thalamus, optic radiation fibers run to the visual cortex in teh occipital lobe
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sole function of CN II
carry afferent impulses for vision to the occipital lobe
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4 dimensions of vision CN II works with
- acuity: central vision
- fields: peripheral vision
- pupillary dilation/contraction: reflex response to light
- accommodation reflex: dealing w depth of field
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how to describe the quadrants of the visual field
- superior medial/nasal
- superior lateral/temporal
- inferior medial/nasal
- inferior lateral/temporal
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monocular blindness - associated w lesion of what CN? and w what itis?
CN II or optic neurits of MS
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bitemporal hemianopsia - describe. associated w what pathology?
- lose vision in temporal fields, so it's as if pt is wearing blinders
- associated w pituitary tumors and CN II lesions
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homonymous hemianopsia - describe. associated w what pathology?
- loss of vision in temporal field of one eye and and nasal field of the other
- associated w optic tract lesions - CVA, or CN II lesions
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homonymous quadrantopsia - description, and how to tell if it's a temporal or parietal lobe lesion
- like it sounds - defect in same quadrant of both eyes
- temporal lobe lesion: defect in an upper quad
- parietal lobe lesion: defect in a lower quad
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visual field confrontation test
- pt covers one eye and look forward
- PT brings her hand forward from behind pt's head in the dir of each of the quadrants and notes when pt first sees it - should seeit when t ges a few cm past teh plane of their eye
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pupillary light reflex - how it should go
shine a penlight directly into either eye, and both pupils should constrict
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direct reflex vs consensual reflex in pupillar light reflex
- direct: constriction in the lighted eye
- consensual: constriction in the other
document it as present, absent, diminished
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which CN are involved in the pupillary light reflex, and how?
- CN II - gets the sensory input and sends up afferent impulses
- CN III - occulomotor nerve, take a wild guess
when evaluating what's not working, please remember that you have a diff nerve for each side of your head, so CN III on the left may be fine while on the right your pupil is a grapefruit moon
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CN II accomodation test
- bring an object to a pt's face from 1-2 feet away as pt stares at object
- normal: constriction and convergence of both eyes
- abnormal: lack of const and/or conv
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PERLA
Pupils Equal, Round Light Reactive, Accomodating
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anisocoria def
unequal pupil diameter
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fixed ppil
- non-reactive to light or accommodation
- this is worrisome
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argyll robertson upil
pupil is small, doesn't react to light, but does accomodate
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CN III, CN IV, CN VI - names, and what they do as a team
and a lovely test for them
- III: occulomotor
- IV: trochlear
- VI: abducens
- they do the slow eye motions used to maintain vision on a moving target
can test these by asking pt to watch your finger as you trace out an H
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ecchymosis
a small hemorrhagic spot in the skin or mucous membrane
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When using the H test to test CNs III, IV, and VI, what are common complaints? How to document?
- diplopia, blurred vision, unequal tracking
- you might see nystagmus
- document the areas of min and max troubles
- or write EOMI - extra ocular muscles intact
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saccades
rapid movement of the eye from one point of fixation to another (like looking from a book to a cat at the door w/o moving your head)
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how to test for saccades
- w your hands far apart, have the pt look at your finger w/o moving head
- test in all four planes to assess extraocular muscles
- look for deviation in each eye, each movement, smoothness, speed, nystagmus, vertigo, diplopia, blurring
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which CN is responsile for 75% of eye movements?
CN III - occulomotor nerve
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testing CN III, test movements in this order:
- sup: superior rectus muscle
- inf: inf rectus
- nasal: medial rectus
- sup nasal: inf oblique
- eyes wide open: levator palpabrae
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single function of CN IV
control of superior oblique muscle - that pulls the eye in the inferior nasal direction
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what will you notice about a pt with a CN IV lesion?
- the eye can't track past midline
- consistent with a midbrain lesion
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snigle function of CN VI
abd eye past midline -- the lateral rectus muscle
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why is it common to injur CN VI
abducens - bc it's a long nerve, so it has increased susceptibility to intracranial pressure (ICP)
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strabismus
wakness/paralysis of extra ocular movements(EOM)
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lateral strabismus
"wall eyed" - loss of medial rectus (CN III)
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medial strabismus
cross-eyed - loss of lateral rectus (CN VI)
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hypertropia vs hypotropi
- hypertropia: eyes turned upwards, loss of downward gaze
- hypotropia: eyes turned downwards, loss of upward gaze
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CN V - name and its three domains
- trigeminal nerve
- optic (sensory)
- maxillary (sensory of upper and middle face)
- madibular (sensory and motor - muscles of mastication)
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trigeminal neuralgia
horrid, horrid pain due to trouble in CN V
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CN VII - name and its domain
- facial nerve
- motor: muscles of facial expression
- sensory: to stapes - hearing
- taste: ant 2/3 of tongue
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hyperaccusis
- problem w CN VII's sensory (to stapes) section
- hearing is too sensitive
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which muscle works when you grimace?
platysmus!
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testing for CN VII - facial
actions, and muscles involved
- squeeze eyes shut: orbicularis orcularis
- smile widely: zygomaticus
- wringkle foreheatd: frontalis
- frown
- purse lips
- grimace: platysmus
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if you see drooping on someone's face, how to tell if it's a CNS or PNS problem
- CNS: corticobulbar tract - droop of lower contralateral face
- PNS: (CN VII palsy) droop of entire inpsilat face
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CN VIII name and it's domains
- vestibulocochlear
- vestibular: balance, stable eye regardless of head pos
- cochlear: hearing
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vestibular ocular reflex (VOR)
- allows eyes to track a moving object regardless of head position or movement
- this is the primary output of the vestibular nerve
- deficits can be peripheral or central
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how to test the VOR (vestibular ocular reflex)
put finger in front of pt, and have pt move head up and down and side to side while trying to continually stay focused on the finger
VOR 2 - PT should move finger in opp dir of the pt's moving head
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thre things to note in the VOR
- could pt keep figner in focus?
- did pt feel vertigo?
- did PT see any nystagmus in pt's eyes?
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how to make the VOR more complicated (nauseating)
have pt stand one foot right in front of the other or in a single legged stance
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nystagmas
- oscillating eye movement
- slow and fast phase, and it's named for the direction in which it moves fast
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vertigo - what it means, and what it doesnt
- spinning, jumping, telescoping (body shooting up and down), or pulsing sensation
- it's not the same as dizziness or light headedness
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signs that vestibulopathy is from a CNS lesion
- direction changing nystagmus
- rotory OR linear components to nystagmus
- can be separate from vertigo
- unable to supress w fixation
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sings that vestibulopathy is from a peripheral lesion
- unidirectional nystagmus
- rotary AND linear components
- matches with vertig
- supresses w fixation
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Benign Paroxysmal Positional Vertigo (BPPV)
- calcium carbonate crystals ion the semicircular canals with the perilymph messing up how the perilymph gives signals to the hair cells
- this is the most common vestibular complaint
- diagnosable by Hallpike Dix test
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Hallpike Dix test is to diagnose what?
benign paroxysmal positional vertigo
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Hallpike Dix test - how?
- pt in long sit
- look up and over left shoulder
- PT rapidly brings torso into supine and neck into ext while pt keeps looking up over shoulder
- wait 20-60 sec for nystagmus
- when it clears, return fast to sitting position
- see reversal of nystagmus
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CN IX and CN X
- glossopharyngeal and vagus
- taste in post 1/3 of tongue
- gag reflex
- all parasymphatheti
- recurrent laryngeal nerve to vocal cords
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dysphonia
hoarseness or quietness of voice
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indications of CN IX and X trouble
- dysphagia - trouble swallowing
- dysphonia - hoarsness or quietness of voice
- absent gag reflex
- deviation of soft palate to unaffected side
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CN XI
- spinal accessory nerve
- controls trapezius - shrugging shoulders
- SCM - rotate head
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CN XII
- hypoglossal n
- motor control of tongue
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how to tell if a motor injury to the tongue is from CNS or PNS
- central lesion: deviates away from side of lesion w/o atrophy or fibrillations
- peripheral lesion: deviates towards side of lesion with atrophy and fibrilations
- (component of dysphagia and dysarthria)
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