Lecture 30- anatomical cases- cranial nerve lesions

Question 1

What is anisocoria

Answer 1

Unequal pupil sizes

Question 2

What is miosis

Answer 2

Pathological constriction of the pupil, indicates a possible disruption of sympathetics to the eye

Question 3

What structure could be damaged with miosis

Answer 3

Internal carotid artery plexus which carries SNS to dilator muscles

Question 4

What is mydriasis

Answer 4

Pathologically dilated pupils, indicates disruption of PNS to eye

Question 5

What structures could be damaged with mydriasis

Answer 5

PNS to eye carried from CN III to short ciliary ganglion to constrictor muscles

Question 6

Pupillary response example: if we shine a light in the right eye and we get no direct or consensual response, but if shined into the left eye you get both a consensual and direct response. Where is the lesion

Answer 6

Optic nerve on the right side. Able to get a direct and consensual response when shinin into left side because optic nerve unmanaged on that side and the pretectal nuclei provides bilateral innervation to E-W nucleus and therefore to constrictor muscle on right side

Question 7

Pupillary response example: you shine a light into the right eye and there is a known lesion to the optic chiasm- do you expect a direct and consensual response

Answer 7

Yes, because you still get visual information from the temporal side of right eye that can send bilateral information to pretectal nuclei—> E-W and then constrictor to both eyes

Question 8

Pupillary light reflex example: there is a known lesion to the optic tract, you shine a light in the right eye and get direct and consensual response why/how?

Answer 8

Bilateral innervation from pretectal—> E-W—> CN III—> short ciliary ganglion—-> constrictor muscles in both eyes

Question 9

Pupillary light reflex example: you shine a light into the left eye and you get no direct response but you get a consensual response. Where is the lesion

Answer 9

CN III- because you have bilateral innervation from pretectal nuclei giving you constriction to left eye via CN III—> short ciliary ganglion but since there is a lesion on CN III you can’t access direct constrictor muscles

Question 10

What are the symptoms of horners syndrome

Answer 10

Recession of eye into orbit (enophthalmos)due to loss of tone from smooth muscles in peri orbital, prolapse of third eye lid, narrowing of palpebral fissure, constriction of pupil

Question 11

What structures are damaged in Horner’s syndrome

Answer 11

Disruption to SNS innervation, internal carotid plexus

Question 12

What cranial nerves are being tested during the menace test

Answer 12

Sensory innervation to CN II (optic) and motor innervation to CN VII (facial)

Question 13

What is strabismus

Answer 13

Disorder in which the two eyes do not line up in the same direction or do not look at the same object at the same time

Question 14

strabismus example: left eye is locked in the down and out position

What extraocular muscles are contracting, what muscles are paralyzed, which cranial nerve is lesion

Answer 14

Contracting: lateral rectus and dorsal oblique (CN VI and IV)

Paralyzed: medial rectus and dorsal oblique

Cranial nerve lesioned: CN III(oculomotor)

Question 15

Strabismus example:

Left eye is unable to look out

Which extraocular muscles are contracting?

Which muscles are paralyzed

Which cranial nerve is lesioned

Answer 15

Contracting: medial rectus and dorsal oblique

Paralyzed: lateral rectus and ventral oblique

CN lesioned: CN VI

Question 16

What is ptosis

Answer 16

Drooping of upper eyelid and narrowing of palpebral fissure

Question 17

What cranial nerve and muscle are implicated in ptosis

Answer 17

Levator palpebrae superioris and CN III

Question 18

What cranial nerves are being tested in the corneal blink reflex

Answer 18

Sensory component of V1 and motor component of VII to orbicularis oculi

Question 19

Cranial nerve dysfunction example: patients entire right side of face is drooping:

What muscles are impacted?
What cranial nerve is impacted?
Where might the lesion be located?
Would you expect that the patient can completely close the eyelids on both sides

Answer 19

Muscles: muscles of facial expression

CN: VII (facial)

Where might the lesion be located: stylomastoid foramen

Would not expect patient to be able to close eyes on right side since obicularis oculi is innervated by CN VII

Question 20

Cranial nerve dysfunction example: patient presents with concave, indentation appearance on the top of left side of head

What muscles are impacted
What term best describes the loss of these tissues
What nerve innervates these muscles
Where might the lesion be located

Answer 20

Muscles: temporalis muscle
Term: atrophy
CN involved: V3- innervates muscles of mastication
Location of lesion: oval foramen