Notes 1a Flashcards
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.
Optic nerve provides input to
- the superior colliculus (for reflex saccades)
- lateral geniculate nucleus (relay of the visual pathway)
- pretectal nucleus (relay of the light reflex)
- the suprachiasmatic nucleus (the circadian pacemaker).
Anterior ischemic optic neuropathy
- Results from ischemic insult to the optic nerve head
- Presents with acute, unilateral, painless visual loss
- Fundosdcopic examination: optic edema (unless retrobulbar—> posterior ischemic optic neuropathy), hyperemia with splinter hemorrhage and crowded and cupless disc
- Optic disc in giant cell arteritis is pallid not hyperemic
Chronic optic neuritis
- Features: persistent visual loss, color desaturation, persistent APD
- will eventually lead to optic atrophy with shrunken and pale disc
Nerves in the cavernous sinus
3,4,V1,V2,6
Cavernous sinus syndrome? Assoc with what infection
proptosis
blurry vision
Mucormycosis
Lesion in the facial nerve nucleus in the pons will cause?
Upper and lower facial paralysis
A stroke in this area is unlikely to be isolated, expect some damage to surrounding structures in CN6 and corticospinal tract
Causes of bilateral facial nerve palsy?
MS
Sarcoidosis
Lyme
Prognosis of Bells is favorable if recovery is seen in first ___ days
21
Crocodile tears phenomenon?
- results when misdirected regenerating facial nerve axons originally supplying the submandibular and sublingual salivary glands, innervate the lacrimal gland through the greater petrosal nerve.
Causes lacrimation while smelling food/eating
Synkinesis after Bell’s palsy
- some axons from the motor neurons to the labial muscles involved in smiling may regenerate and misdirect to the orbicularis oculi, which results in closure of the eye on smiling. The reverse may also occur and result in twitching of the mouth on blinking.
Characteristics of central nystagmus
- non-fatiguing, absent latency, not suppressed by visual fixation, duration of nystagmus > 1min and may occur in any direction
Characteristics of peripheral nystagmus
- slow drift of the eyes away from the target in one direction (toward the affected side and away from the unaffected side), followed by a fast cortical corrective movement to the opposite side (toward the unaffected side, away from the affected side).
- amplitude of nystagmus increases with gaze towards the unaffected ear and away from the affected one
Cold caloric testing
Cold water: eyes deviate slowly towards the ipsilateral ear (tonic deviation of the eyes toward the cold water)
After 20ish seconds, nystagmus appears and may persist for up to 2 mins
The fast phase of nystagmus reflects the cortical correcting response and is directed away from the side of the cold water stimulus.
If cortical circuits are impaired (comatose state), the nystagmus will be suppressed and not present, and only the eye deviation will be present (if brainstem is intact).
The anterior belly of the digastric nerve is innervated by? Posterior belly?
CN V, CN 7
Facial nerve pathway
Exits brainstem through internal auditory meatus and synapses at geniculate ganglion where it has several branches
Branch 1: into greater/lesser petrosal nerve
Branch 2: nerve to stapedius
Branch 3: chorda tympani → joins lingual nerve of V3 where it carries taste for ant ⅔ of the tongue.
Nerve then stylomastoid foramen where it has the facial motor branches.
All glands in the head and face are innervated by facial nerve except?
parotid gland, glossopharyngeal
nucleus tractus solitarius is involved in
taste and baroreceptor reflex
nucleus ambiguus is involved in
innervation of the muscles of the larynx and pharynx
dorsal motor nucleus of the vagus nerve is involved in
cranial nerve nucleus of CNX responsible for parasympathetic visceral function (GI, lungs, etc)
V1 supplies sensation to
- upper half of cornea, conjuctiva and iris, as well as dura mater of the anterior cranial fossa, falx cerebri, and tentorium cerebelli
V2 supplies sensation to
- lower eyelid, upper lip, lower half of cornea, conjuctiva and iris, test of the upper jaw and dura matter of the middle cranial fossa
All the contents of the cavernous sinus
- ICA (siphon)
- postganglionic sympathetic fibers
- cranial nerve VI on the medial wall (adjacent to the sphenoid sinus)
- cranial nerves III, IV, V1, and V2 are found along the lateral wall
Occlusion of the artery of percheron causes?
infarct in medial thalamic structures
Recurrent artery of Heubner
branch of ACA that supplies:
anterior limb of the internal capsule
inferior head of caudate
anterior globus pallidus
Lacunar stroke types: Pure motor
caused by occlusion of the lenticulostriate branches affecting the posterior limb of the internal capsule
Lacunar stroke types: Pure sensory
lacune in the thalamus
Blood supply to the cerebellum
mostly SCA (upper) and PICA (lower)
Parinaud’s Syndrome
- lesion in dorsal midbrain
- characterized by supranuclear paralysis of eye elevation, defect in convergence, convergence-retraction nystagmus, light-near dissociation, lid retraction (Collier’s sign), and skew deviation of the eyes.
Alexia without agraphia
Left occipital infarct involving the splenium of the corpus callosum
(R visual cortex cannot connect to language center on the L = can write but can’t read)
