Cranial Nerve Exam Flashcards
1
Q
When are cranial nerves a priority to assess
A
- testing should occur in the presence of known or suspected injury to the brain, brainstem, or upper cervical spine
- if there is a known or suspected progressive disease that affects the brain or brainstem
- if pt reports any sudden or unexplained change in any function controlled by a cranial nerve
- if pt demonstrates any side-to-side differences in facial expression
- if there is any notable atrophy in the muscles of the face or lateral neck
2
Q
Mnemonic to remember the order and sensory/motor function of the cranial nerves
A
- Order: oh (olfactory) oh (optic) oh (oculomotor) to (trochlear) touch (trigeminal) and (abducens) feel (facial) very (vestibulocochlear) good (glossopharyngeal) velvet (vagus) so (spinal accessory) heaven (hypoglossal)
- Sensory/Motor Function: some say marry money but my brother says big brains matter more
3
Q
How to asses CN 1/olfactory
A
- pt closes eyes
- using distinctive smelling items (2-3), ask pt to smell the items one at a time for each nostril
- pt should be able to identify the odor & strength of odor should be equal side-to-side
4
Q
How to assess CN 2/optic
A
- using a Snellen eye chart ask pt to read the lines with progressively small letters
- using a penlight shine light into pt’s eye, normal response is constriction of the contralateral pupil
5
Q
Describe the different possible findings from a pupillary light reflex exam
A
- CN 2/optic lesion: absent ips direct with absent contra consensual and intact contra direct with ips consensual
- CN 3/oculomotor: absent ips direct with intact contra consensual and intact contra direct with absent ips consensual
6
Q
Pupillary light reflex
A
CN 2: light shined on lesion side there is no constriction of either eye
CN 3: light shined in lesion side no constrict and light shined on non lesion side the lesion eye with not have consensual constrict
7
Q
How to assess CN 3/oculomotor
A
- assess ability to elevate both eyelids, if lesion drooping eyelid does not retract with upward gaze
- using a penlight shine light into pt’s eye & assess constriction of ipsilateral pupil
8
Q
Describe the near triad accommodation reflex
A
- Accomodation: change in the shape of the lens of the eye through action of the ciliary muscle following activation of the parasympathetic nucleus of CN 3
- Convergence: adduction of the eyes bilaterally through activation of main nucleus of CN 3
- Miosis: constriction of the pupil due to activation of parasympathetic nucleus of CN 3
9
Q
Describe eccentric gaze holding nystagmus
A
- to avoid normal physiologic nystagmus the edge of the iris in the adducting eye should align vertically with the superior medial edge of the lower eyelid
- in this position the eyes are deviated about 30 degrees from center & only pathologic nystagmus will present at this eye position
10
Q
How will the eye present with a CN 3/oculomotor lesion vs a CN 4 lesion vs a CN 6/abducens lesion
A
- CN 3/oculomotor: eye is deviated down and outward
- CN 4/trochlear: eye is deviated slightly upward
- CN 6/abducens: eye is deviated inward/adducted
11
Q
CNs that control the eye movement during an H test
A
- Eyes looking right: R eye = CN 6, L eye = CN 3
- Eyes looking left: R eye = CN 3 , L eye = CN 6
- Eyes looking down & right: R eye = CN 3, L eye = CN 4
- Eyes looking down & left: R eye = CN 4, L eye = CN 3
- Eyes looking up & right: R eye = CN 3, L eye = CN 3
- Eyes looking up & left: R eye = CN 3, L eye = CN 3
12
Q
What eye muscle does CN 4/trochlear and CN 6/abducens innervate
A
- CN 4/trochlear innervates superior oblique
- CN 6/abducens innervates lateral rectus
13
Q
Lists the muscles of the eye, their actions, and their innervations
A
- Medial rectus: abducts eye, CN 3
- Lateral rectus: adducts eye, CN 6
- Superior rectus: elevates abducted eye, CN 3
- Inferior rectus: depresses abducted eye, CN 3
- Superior oblique: depresses adducted eye, CN 4
- Inferior oblique: elevates adducted eye, CN 3
14
Q
Coordination of eye movements via the medial longitudinal fasciculus (MFL)
A
- coordination of 2 eyes is maintained via synergistic action of the extraocular muscles
- requires connections among the cranial nerve nuclei that control eye movements
- the eye moves toward the right & the MFL then conveys a signal from the eye muscle nucleus to the left oculomotor nucleus
- the left oculomotor nerve then activates a muscle on the left eye to move it in the same direction as the right eye
- signals conveyed by the MLF coordinate head & eye movements by providing bilateral connections among vestibular & ocular motor nuclei in the brainstem & spinal accessory nerve nuclei in the spinal cord
15
Q
Vision effects due to an acute vs chronic lesion to CN 3, 4, 6, or the MLF
A
- if disorder is acute, double vision will occur bc images of objects will not coincide one the retinas
- if the disorder is chronic, the nervous system may suppress vision from the deviant eye & double vision will be absent, however with the suppression of vision from one eye the person will lose depth perception
16
Q
How to assess the sensory component for CN 5/trigeminal
A
- with pt’s eyes closed use a cotton ball to lightly touch the pt’s face
- areas to touch: forehead, cheeks, & lateral jaw
- the pt should feel the touch equally on the right & left sides
17
Q
How to assess the motor component for CN 5/trigeminal
A
- palpate the pt’s masseter & temporalis muscles bilaterally for strength of contraction as the pt clenches their jaw
- ask the pt to hold the jaw open slightly & then provide resistance to mandibular closing or lateral motion
- pt should be able to hold the position against moderate force
18
Q
Describe the corneal “blink” reflex
A
- ophthalmic neurons (CN V1) of the trigeminal nerve provide the afferent (sensory) limb of the corneal blink reflex
- when the cornea is touched info is relayed to the spinal trigeminal nucleus via the trigeminal nerve
- from the spinal triigeminal nucleus interneurons convey info bilaterally to the facial nerve (CN 7) nuclei
- CN 7 then reflexively activate muscles to close the eyelids of both eyes
19
Q
How to assess CN 7/facial
A
- assess motor function by asking the pt to smile, frown, elevate or depress the eyebrows, & puff out the cheeks; assess for symmetry
- assess sensory function (taste) ask pt to close their eyes & stick out their tongue; place something sweet on the anterior portion of the tongue & ask th pet to identify the taste
20
Q
Describe the CN 7/facial motor pathways
A
- Corticobrainstem tracts provide bilateral signals to the region of the facial nucleus that innervates the muscles in the upper face (ex: both the R/L motor cortex send signals to the R facial nerve to close the R eye)
- Corticobrainstem tracts send contralateral signals to the region of the facial nucleus that innervates muscles of the lower face (ex: L motor cortex sends signals to the R facial nerve which then signals the muscles that move the R side of the lips)
21
Q
Describe the presentation of a CN 7/facial lesion
A
- lesion results in ipsilateral paralysis of all facial expression muscles
- corticobulbar fibers from cerebral cortex project to the facial motor nucleus in the brainstem
- dorsal 1/2 of the facial motor nucleus receives fibers from both sides of the cortex which supplies motor innervation to both sids of the face via CN 7
- ventral 1/2 of the facial motor nucleus receives corticobulbar fibers from the contralateral cerebral cortex which supplies motor innervation to the contralateral lower half of the face via CN 7
22
Q
Presentation of a stroke versus lesion to the facial nerve
A
- Stroke: only the contralateral lower half of the face will be affected
- Facial nerve lesion: one whole side of the face will be affected
23
Q
What other functions does the facial nerve include
A
- Lesions may also result in impaired lacrimation (tear production/lubricate the eyes), impaired taste in the anterior 2/3 of the tongue, and/or impaired corneal “blink” reflex
24
Q
How to assess CN 8/vestibulocochlear
A
- pt’s eyes should be closed, hearing can be assessed by rubbing the pads of your thumb & index finger together next to one of the pt’s ears
- bilaterally symmetrical hearing is expected unless a known hearing loss is present
- test one ear at a time
25
Special tests for hearing via CN 8/vestibulocochlear
- Rinne Test: place & hold the stem of a tuning fork on the mastoid bone, when the pt no longer hears it, move the vibrating tuning fork tines into the air about 1in from the ear canal
- Weber Test: place & hold the stem of a tuning fork on the top of the pt's head, ask the pt if the sound is louder in one ear than the other, normally the sound is equally loud in both ears
26
Describe ampulla and cupula
- Ampulla: enlargement of semicircular canal, hair cells contained in each ampulla & otolith organ convert displacement due to head motion into neural firing, the hair cells rest on a tuft of blood vessels, nerve fibers, & supporting tissue called the crista ampullaris
-Cupula: diaphragmatic membrane that overlies each crista & completely seals the ampulla from the adjacent vestibule
27
Describe the head impulse test (VOR)
- it test the vestibuloocular reflex (VOR)
- clear the cervical spine before performing
- ask the pt to stay looking at my nose
- place pt's head in slight cervical flexion
- passively turn pt's head to right & left & ensure they're relaxed
- head turn should be rapid (>200 deg/sec), unpredictable, & small amplitude (10-20 deg)
- abruptly stop & observe the pt's eyes
- normally the pt's eyes remain fixed on the examiner's nose
- lesion on left = pos. head impulse to the left
28
Describe dynamic visual acuity (VOR)
- this tests the pt's ability to maintain gaze on an object while the head is moving
- this requires the VOR, an autonomic adjustment of eye position to compensate for head movement
- ask pt to read an eye chart while you passively rotate the pt's head at a frequency of 2 Hz
- pt's with intact VOR will have less than one line loss of accuracy during head movements compared with their acuity when the head is stable
29
How to assess CN 9/glossopharyngeal and CN 10/vagus
- CN 10/vagus: ask pt to open their mouth & say "ahh", observe the uvula (no later deviation should be present), listen for loss of phonation (CN 10)
- CN 9/glossopharyngeal: ask the pt to swallow several times, observe for & ask about any difficulty with this action (CN 9)
- CN 9/glossopharyngeal: test the gag reflex by carefully moving the tongue depressor toward the back of the pt's throat until the gag reflex is elicited (CN 9)
30
How to assess CN 11/spinal accessory
- ask pt to shrug their shoulders
- press downward, asking the pt to hold the position
- the pt should be able to resist your force bilaterally
- observe for atrophy of the trapezius or sternocleidomastoid muscles (compare side to side)
31
How to assess CN 12/hypoglossal
- ask the pt to stick out their tongue & observe for any side-to-side deviation or atrophy
- may also ask the pt to move the tongue from side to side, obsering for smooth motions
- positive test = "lick your lesion", tongue deviates toward the affected side
32
Visual field confrontation test
- should be 18 inches away from the pt's eyes
- smooth pursuit should not be fast
33
Dysarthria for CN 7, 9, and 12
- CN 7/facial: pa, pa, pa
- CN 9/glossopharyngeal: ka, ka, ka
- CN 12/hypoglossal: la, la, la
