Cranial Nerves--Testing

Front 1

What's Horner syndrome?

Name the 4 symptoms

Back 1

Ptosis
Miosis
Anhydrosis
Enophthalmos

--ptosis (drooping upper eyelid from loss of sympathetic innervation to the Müller or superior tarsal muscle
--miosis (constricted pupil..loss of innervation to pupillary dilator muscle)
--Enophthalmos (the impression that the eye is sunk in)
--anhidrosis (decreased sweating)

Front 2

pupillary light reflex

whats the afferent and efferent?

Back 2

Amount of light entering eye is regulated by pupillary light reflex.


Afferent limb is optic nerve
Two efferent limbs – one to each sphincter pupillae
Hence, reflex is consensual.
Consensual = stimulus should evoke pupillary constriction in both eyes


The pupillary reflex pathway begins with retinal ganglion cells, which convey information from photoreceptors to the optic nerve (via the optic disc). The optic nerve connects to the pretectal nucleus of the upper midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus, axons connect to neurons in the Edinger-Westphal nucleus, whose axons run along both the left and right oculomotor nerves. Oculomotor nerve axons synapse on ciliary ganglion neurons, whose axons innervate the constrictor muscle of the iris.

Front 3

where's the lesion?

If neither pupil constricts
if only one pupil constricts

Back 3

-afferent limb (CN II)
-CN III (ipsilateral to deficit)

Front 4

common causes of damage to the oculomotor nerve are:
--Aneurysm of ______
--Pressure on oculomotor nerve due to temporal herniation through tentorial incisure.
Such herniation may pressage imminent death.

Back 4

posterior communicating artery

Front 5

how do sympathethics get to the eye? (and innervate dilator pupillae)

Back 5

Damage to hypothalamus or pons, and some opiates, result in constricted, reactive pupils, signs of sympathetic impairment.

(reactive to light->3 is intact)

Front 6

what's this?

Back 6

down and out eye

Front 7

pathophys of down and out eye?

Back 7

caused by lesion in CN III!!

“Down and out” eye caused by unopposed action of lateral rectus (VI) and superior oblique (IV).
DOWN bc of SUPERIOR OBLIQUE
OUT bc of LATERAL RECTUS
1) ptosis: due to inactivation of levator palpebrae superioris


2) dilated pupil: sphincter pupillae muscle inactive (parasympathetics); unopposed action of dilator pupillae:


elevation of eyebrow due to contraction of frontalis to compensate.

Lack of accommodation: ciliary m. inactive (parasympathetics)




Strabismus (inability to direct both eyes to same object) producing diplopia;

Front 8

what's wrong?

Back 8

Patient cannot abduct left eye: left abducens (VI) palsy

Front 9

which CN is affected?

Patient has double vision when looking down (going down stairs, reading book), and when looking straight ahead, unless head tilted to left.

Back 9

trochlear

superior oblique intorts the eye!!! if damaged, unopposed extortion

Front 10

what nerve is this guy testing?

Back 10

corneal reflex: 5, 7
trigeminal (afferent)
facial (efferent)

Front 11

Testing CN 8

Back 11

Front 12

how can you test 9, 10?

Back 12

Swallow
Dysphagia for liquids and solids
Palate rise
Gag Reflex (A & E)
Voice exam

Front 13

what's being tested?

Back 13

Tongue movement
Tongue deviation
Deviated to the affected side
Atrophy
Fasciculations



Upon protrusion, the tongue will deviate TOWARD the side of the lesion (i.e., same side). This is due to the unopposed action of the genioglossus muscle on the normally innervated side of the tongue (the genioglossus pulls the tongue forward). Remember, the genioglossus arises laterally in the tongue and inserts on the midline of the mandible.

Front 14

What is the connection between the cranial nerves responsible for horizontal eye movements?

Back 14