Cranial nerves & their examination Flashcards
CN I
function
how to test it
clinical finding in case of deficit?
olfactory
smell perception
food test
decreased/absent sense of smell
CN II
function
how to test it
clinical finding in case of deficit?
optic nerve
sensory: vision, receives light stimulation via the retina
test by passing obstacles, pupillary light reflex, menace response, visual placing
vision loss if deficit
CN III
function
how to test it
clinical finding in case of deficit?
oculomotor
motor: muscles that move the eyeball and lift the upper eyelid
parasymp: pupil constriction
eye position and movement (like that test for nystagmus) and pupillary light reflex
if deficit, strabismus, mydriasis
CN IV
function
how to test it
clinical finding in case of deficit?
trochlear
motor: dorsal oblique m. of the eyeball
test by eye position and eye movement tests
strabismus if deficit
CN V
function
how to test it
clinical finding in case of deficit?
trigeminal
sen: cornea, canthi, nasal septum, oral cavity face
motor: mastricatory mm.
test by palpebral and corneal reflexes, nasal mucosa sensitivity, facial pinching, dropped jaw
deficit if decreased facial sensitivity, disturbed chewing, open mouth, m. atrophy
CN VI
function
how to test it
clinical finding in case of deficit?
abducent
mot: retractor bulbi mm., lateral rectus mm.
test by eye position and movement
deficit if strabismus
CN VII
function
how to test it
clinical finding in case of deficit?
facial nerve
sen: rostral tongue & palate
mot: facial mimical mm.
parasymp: lacrimal & salivary glands
test with palpebral and corneal reflexes, menace, facial pinching and symmetry
deficits if asymmetry of facial parts, no blinking, KCS
CN VIII
function
how to test it
clinical finding in case of deficit?
vestibulocochlear
sen: balance and auditory
test with posture, gait, eye position, hearing/BAER
deficits if head tilt, nystagmus, strabismus, ataxia, falling, circling, hearing loss
CN IX
function
how to test it
clinical finding in case of deficit?
glossopharyngeal
sen: caudal third of tongue & pharyngeal mucosa (taste too)
mot: mm. of pharynx and palatine stuff
parasymp: salivary glands
test with swallowing reflex, laryngoscopy
deficit if difficulty swallowing
CN X
function
how to test it
clinical finding in case of deficit?
vagus
sen: larynx & pharynx
mot: larynx, pharynx & esophagus
parasymp: thoracic and abdo organs
test with swallowing reflex & oculocardial reflex
deficit ifdysphagia, inrpiratory dyspnea, voice change, regurg.
CN XI
function
how to test it
clinical finding in case of deficit?
accessory
mot: trapezius muscle
test with palpation
deficit if atrophy
CN XII
function
how to test it
clinical finding in case of deficit?
hypoglossal
mot: tongue mm.
test with tongue retraction
deficits if tongue atrophy, asymmetry
12 pairs of cranial nerves that originate from
the brainstem, except for olfactory and optic nerves
Testing them helps tell you:
- Is the neurological problem related to the brain?
- Which part of the brain: forebrain, cerebellum, brainstem?
- Central vs. peripheral problem?
Don’t forget to eval. facial symmetry. You can find: (2)
drooping/ptosis
muscle atrophy
Describe evaluation of Position of the eyes (strabismus). (5)
The extraocular muscles are innervated by
oculomotor nerve (III), trochlear nerve (IV)
and abducent nerve (VI).
- breed-related strabismus (e.g. Chihuahua)
- positional (pathological) strabismus
To test: raise the head upwards and watch which way the eyes look.
Strabismus is often associated with vestibular disorders.
Describe Pupil size and pupillary light reflex (PLR).
Afferent,
destination,
efferent
➢ Afferent: optic nerve (II)
❖ brainstem (oculomotor nuclei)
➢ Efferent: oculomotor nerve, parasympathetic part (III)
NB! This Does not test the vision! (reflex pathway does not include cerebral cortex)
Note:
* anisocoria: different pupil sizes
* head trauma
* with fear & pain the pupils may be dilated
Use a strong spotlight!
Describe the Palpebral reflex.
Afferent,
destination,
efferent
➢ A: trigeminal nerve (V)
❖ brainstem
➢ E: facial nerve (VII)
Carefully tap both nasal and temporal canthi!
Describe the Menace response.
Afferent,
destination,
efferent
➢ A: optic nerve (II)
❖ forebrain, cerebellum, brainstem
➢ E: facial nerve (VII)
- present at 10-12 weeks of age, not younger
- don’t touch the hair, you can cover the other side of the eye with your hand
- cats may not show it due to stress, up to 30%
If menace response is absent? Localize the problem.
Because the menace response’s
➢ A: optic nerve (II)
➢ E: facial nerve(VII)
The problem must be related to CN II, forebrain
or CN VII!
If menace response and PLR are both absent, then the damage is where?
at the optic nerve CN II!
Because the menace response and PLR have the same afferent nerve CN II, but a different efferent nerve.
If only the menace response is absent and PLR is
normal, the damage cannot be CN II.
Facial nerve CN VII is responsible for blinking.
If the menace response is absent, but the palpebral reflex is functioning, the problem cannot be related to CN VII.
If the menace response and the palpebral reflex
are both absent, then the problem is where?
Localized to the facial nerve CN VII!
Facial nerve CN VII is responsible for blinking.
If the menace response is absent, but the palpebral reflex is functioning, the problem cannot be related to CN VII.
If the menace response is absent but the PLR
and palpebral reflex are functioning, where is the
damage?
is in forebrain.
Describe the Corneal reflex.
Afferent and efferent nerves?
When do you test this?
➢ A: trigeminal (V)
❖ brainstem
➢ E: facial nerve (VII, blinking of the eye), abducent nerve (VI, retraction of the eyeball)
- Test only if the palpebral reflex is decreased/absent!
Describe Nystagmus.
+ afferent and efferent related tracts
Physiological nystagmus is an oculocephalic reflex, which stabilises the image on the retina during head movement. If this is missing, you have a brainstem injury.
➢ A: vestibular part of the vestibulocochlear nerve (VIII),
❖ brainstem
➢ E: oculomotor nerve (III), trochlear nerve (IV), abducent nerve (VI)
Pathological nystagmus can be:
* horizontal, vertical, rotatory
+ pendular (siamese cats, congenitally impaired vision pathway)
To test: First check in normal position. Then check physiological by moving its head side to side.
Next, Turn the animal on its back to induce potential pathological nystagmus.
Fast phase is direction away from the damage!
