Lecture 30- anatomical cases- cranial nerve lesions Flashcards
What is anisocoria
Unequal pupil sizes
What is miosis
Pathological constriction of the pupil, indicates a possible disruption of sympathetics to the eye
What structure could be damaged with miosis
Internal carotid artery plexus which carries SNS to dilator muscles
What is mydriasis
Pathologically dilated pupils, indicates disruption of PNS to eye
What structures could be damaged with mydriasis
PNS to eye carried from CN III to short ciliary ganglion to constrictor muscles
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
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
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
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
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?
Bilateral innervation from pretectal—> E-W—> CN III—> short ciliary ganglion—-> constrictor muscles in both eyes
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
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
What are the symptoms of horners syndrome
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
What structures are damaged in Horner’s syndrome
Disruption to SNS innervation, internal carotid plexus
What cranial nerves are being tested during the menace test
Sensory innervation to CN II (optic) and motor innervation to CN VII (facial)
What is strabismus
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
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
Contracting: lateral rectus and dorsal oblique (CN VI and IV)
Paralyzed: medial rectus and dorsal oblique
Cranial nerve lesioned: CN III(oculomotor)
Strabismus example:
Left eye is unable to look out
Which extraocular muscles are contracting?
Which muscles are paralyzed
Which cranial nerve is lesioned
Contracting: medial rectus and dorsal oblique
Paralyzed: lateral rectus and ventral oblique
CN lesioned: CN VI
What is ptosis
Drooping of upper eyelid and narrowing of palpebral fissure
What cranial nerve and muscle are implicated in ptosis
Levator palpebrae superioris and CN III
What cranial nerves are being tested in the corneal blink reflex
Sensory component of V1 and motor component of VII to orbicularis oculi
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
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
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
Muscles: temporalis muscle
Term: atrophy
CN involved: V3- innervates muscles of mastication
Location of lesion: oval foramen
