Cranial Nerve Examination & Diseases Flashcards
What is CN I? What is it responsible for?
olfactory nerve
mediates the sense of smell
How can CN I be evaluated?
observing the patient sniffing around
(olfactory nerve)
What is CN II? What is it responsible for?
optic nerve
carries visual signals from retina to occipital lobe of the brain
What are 3 ways to evaluate CN II?
- drop a cotton ball and watch the patient follow it to the ground
- menace response - II = visual clue, VII for blink response
- pupillary light response - II = visual clue, III for pupil constriction
What 2 nerves are responsible for the menace response?
II = visual clue
VII = blink response
What 2 nerves are responsible for the pupillary light response?
II = visual clue
III = pupil constriction
(check ipsilateral and contralateral constriction to differentiate response components)
What is CN III? What is it responsible for?
oculomotor nerve
provides motor innervation to most of the extraocular muscles (dorsal, ventral, and medial rectus) and for pupil constriction
What are 2 ways to evaluate CN III?
- observe for physiologic nystagmus when turning head (also involving IV, VI, and VIII)
- observe pupillary constriction in PLR
(oculomotor nerve)
What is CN IV? What is it responsible for? How can it be evaluated?
trochlear nerve
provides motor function to the dorsal oblique extraocular muscle and rolls globe medially
observe for dorsolateral rotation of the pupil
What is CN V? What is it responsible for?
trigeminal - maxillary, mandibular, and ophthalmic branches
provides motor innervation to muscles of mastication (masseter, temporal) and sensory innervation to eyelids, cornea, tongue, nasal mucosa, and mouth
What are 6 ways of evaluating CN V?
- palpate masseter and temporal muscles for symmetry, atrophy, and pain
- check jaw tone
- touch medial septum of nose and look for retraction
- touch the globe and observe for retraction
- palpebral response - blink reflex when touching medial canthus
- pinching the lip and observing for snarl response
(trigeminal nerve)
What is CN VI? What is it responsible for?
abducens nerve
provides motor function to the lateral rectus extraocular muscle and retractor bulbi
What are 3 ways of evaluating CN VI?
- touch globe and observe for retraction
- observe for medial strabismus
- observe for physiologic nystagmus when turning head
(abducens nerve)
What is CN VII? What is it responsible for?
facial nerve
provides motor innervation to muscles of facial expression (eyelids, ears, lips) and sensory innervation to medial pinna; provides taste to rostral tongue and parasympathetic innervation to lacrimal glands and some salivary glands
What are 5 ways to evaluate CN VII?
- menace response
- palpebral response
- observe for facial paralysis, deviation of the nose to one side, or droopy lips
- Schirmer tear test
- ear flick in response to stimulation of medial pinna
(facial nerve)