Notes 1a Flashcards
(113 cards)
Superior rectus function
elevation/intorsion
Inferior rectus function
depression/extorsion
Medial and lateral rectus function
adduction and abduction
Upper and lower eyelids open and close due to ?
7th nerve - orbicularis oculi
Opening of the upper eyelid is also controlled by? Nerve
levator palpebrae superioris, oculomotor nerve 3
Muller’s muscle?
arises from the undersurface of the levator palpebrae superioris
Has SYMPATHETIC innervation, contributes to 1-2mm of eyelid elevation
slight over-elevation of the eyelid may be seen in high sympathetic states (such as fear), and subtle ptosis may be seen in low sympathetic states (such as fatigue)
Horner’s Syndrome
ptosis of upper eyelid
Elevation of lower lid
Pupillary miosis
Facial anhidrosis (if dissection or other lesion extends proximal to the region of the carotid bifurcation, because sweating fibers travel primarily with the ECA and would not be involved in an ICA dissection)
Enopthalmos (posterior displacement of the eye)
Sympathetic pathway affected by Horner’s Syndrome
First order neurons (central neurons) originate in the posterior hypothalamus and descend through the brainstem to the first synapse, located in the lower cervical and upper thoracic spinal cord (levels C8 to T2) —> This spinal segment is called the ciliospinal center of Budge
Second-order neurons (preganglionic neurons) exit the spinal cord, travel near the apex of the lung, under the subclavian artery, and ascend the neck and synapse in the superior cervical ganglion, near the bifurcation of the carotid artery at the level of the angle of the mandible
The third-order neurons (postganglionic neurons) travel with the carotid artery. The vasomotor and sweat fibers branch off at the superior cervical ganglion near the level of the carotid bifurcation and travel to the face with the ECA. The oculosympathetic fibers continue with the ICA, through the cavernous sinus to the orbit, where they then travel with the ophthalmic (V1) division of the trigeminal nerve to their destinations.
How to differentiate between Horner’s lesion affecting 1/2 order neurons vs 3rd order neuron?
Hydroxyamphetamine eye drops
Causes release of stored norepinephrine in the third order neurons.
if no dilation in the eyes with eye drops = 3rd order neuron affected.
Difference between routes of nerve fibers for muscles innervated by CN3
Efferent fibers from the subnuclei of cranial nerve III for the medial rectus, inferior rectus, and inferior oblique proceed ipsilaterally.
Fibers from the subnucleus for the superior rectus decussate
Only cranial nerve that exits dorsally from the brainstem
Cn 4 trochlear
Pathway of the trochlear nerve
Nerve fibers decussate just before they exit dorsally at the level of the inferior colliculi of the midbrain.
motor neurons from each trochlear nucleus innervate the contralateral superior oblique muscle
ventrally, passes between the posterior cerebral and superior cerebellar arteries, lateral to the oculomotor nerve
has the longest intracranial course due to this dorsal exit, making it more prone to injury
CN4 lesion?
vertical diplopia
corrected with head tilting to the contralateral side of lesion (so that the good eye will have same position as affected eye: up and exterior)
CN3 palsies can be caused by damage to what arteries?
SCA, PCA, PCOM, basilar
Nerve passes between PCA and SCA near the basilar tip, in proximity to PCOM and temporal lobe uncus
PPRF receives ipsi/contralateral cortical input?
Contra
Bilateral INO will cause (lesion in both MLFs)
exotropia of both eyes
One a half syndrome
Lesion to both:
- the ipsilateral abducens or PPRF
- ipsilateral MLF
Results in loss of all horizontal eye movements on ipsilateral side, and contralateral eye is only able to move laterally = 1.5 syndrome.
Nerve most likely to be affected by increased ICP?
CN6 = prone to stretching injury as it passes over the petrous ridge.
Adie’s Pupil
Results from a lesion in postganglionic parasympathetic pathway to either the ciliary ganglion or the short ciliary nerves
Caused most commonly by viral etiology
Causes unilateral mydriasis, pupils does not constrict to light or accommodation because the iris sphincter and ciliary muscle are paralyzed
Patients may complain of photophobia, visual blurring, and ache in the orbit
Diagnosis of Adie Pupil
Within a few days to weeks, denervation supersensitivity to cholinergic agonists develops and this is most often tested with low-concentration pilocarpine 0.125%, in which the tonic pupil will constrict but the normal pupil is unaffected by the low concentration
Adies Syndrome
Adies pupil + diminished or absent DTRs
Argyll Robertson Pupil
classically assoc with neurosyphilis
They are characterized by bilateral irregular miosis with little to no constriction to light, but constriction to accommodation without a tonic response as opposed to Adie’s pupil.
Afferent Pupillary Defect/Marcus Gunn Pupil
- Caused by a lesion anywhere from optic nerve to optic chiasm (most commonly in optic neuritis)
- Tested by the swinging light test
- When the light is shone into an eye with a RAPD, the pupils of both eyes will constrict, but not completely. When the light is then moved to stimulate the normal eye, both pupils will constrict further since the afferent pathway of this eye is not impaired. Then, when the light is moved back to shine into the abnormal eye again, both pupils will get larger due to the afferent defect in the pathway of that eye
Features of optic neuritis?
Red desaturation
reduced visual acuity
visual loss
eye pain
***only ⅓ of patients have papillitis with hyperemia and disc swelling. Remaining have only retrobulbar involvement and therefor normal fundoscopic exam.
