Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
102 Cards in this Set
- Front
- Back
what are abnormalities of pupils and eye movements warning signs for
|
signs of pathology in brainstem or CNs
|
|
eye movement disorders and pathways are separated into what two levels
|
1) nuclear and infranuclear pathways 2) supranuclear pathways
|
|
nuclear and infranuclear pathways
|
involve brainstem nuclei of CN III, IV, and VI; peripheral nerves arising from these nuclei; eye movement muscles
|
|
supranuclear pathways
|
involve brainstem and forebrain circuits that control eye movements through connections with nuclei of CN III, IV, and VI
|
|
what eye muscles originate on a tendinous ring at the orbital apex and insert onto the sclera
|
lateral, medial, superior, and inferior rectus muscles
|
|
where does the superior oblique originate
|
sphenoid bone in posterior medial orbit and passes anteriorly through trochlea; inserts on superior surface of eye (intorsion-upper pole inward)
|
|
where does the inferior oblique originate
|
along the anterior medial orbital wall and inserts on the inferior surface of the eye (extorsion-upper pole outward)
|
|
what eye CNs pass through cavernous sinus and enter orbit via superior orbital fissure
|
III (oculomotor), IV (trochlear), and VI (abducens)
|
|
what muscles does CN III innervate
|
all extraocular except lateral rectus and superior oblique; levator palpebrae superioris; preganglionic parasympathetic fibers to pupillary constrictor muscles and ciliary muscles of lens
|
|
trochlear innervates
|
superior oblique
|
|
abducens innervates
|
lateral rectus
|
|
what constitute the somatic motor column of CN nuclei
|
III, IV, VI, along with XII (hypoglossal); all near midline adjacent ventricular system and fibers exit brainstem ventrally near midline (except IV which exits dorsally)
|
|
where are oculomotor nuclei
|
upper midbrain at level of superior collliculi and red nuclei, just ventral to the periaqueductal gray matter
|
|
where does CN III exit brainstem
|
in interpeduncular fossa btwn posterior cerebral and superior cerebellar arteries
|
|
what does the Edinger-Westphal nucleus contain
|
preganglionic parasympathetic fibers
|
|
what are parasympathetics controlling pupil constriction in CN III susceptable to
|
run in superficial portion of nerve as travels in subarachnoid space - susceptible to compression from aneurysms (especially via posterior communicating artery)
|
|
location of trochlear nuclei
|
lower midbrain at level of inferior colliculi and decussation of superior cerebellar peduncle
|
|
abducens nuclei location
|
floor of 4th ventricle under facial colliculi in mid-to-lower pons; exit at pontomedullary jxn
|
|
Dorello's canal
|
abducens nerve travels in-outside dura running btwn dura and skull under petroclinoid ligament
|
|
diplopia causes
|
1) mechanical (fracture) 2) disorders of extraocular muscles (thyroid disease, orbital myositis) 3) disorders of neuromuscular jxn (myasthenia) 4) disorders of CN III, IV, VI and central pathways
|
|
what can cause monocular diplopia or polyopia
|
opthalmological disease, disorders of visual cortex, or psychiatric conditions
|
|
extropia
|
abnormal lateral deviation of one eye
|
|
estropia
|
abnormal medial deviation of one eye
|
|
hypertropia
|
vertical deviation of one eye with respect to other eye
|
|
phoria
|
mild weakness present only with an eye covered (instead of tropia)
|
|
remaining movements of eye with complete disruption of CN III and resting position
|
some abduction (abducens) and some depression and intorsion (superior oblique); eye down and out at rest with complete ptosis and dilated pupil unresponsive to light
|
|
red glass testing with 3rd-nerve palsy
|
diagonal diplopia most severe when looking up and medially with affected eye
|
|
common causes of oculomotor nerve palsy
|
diabetic neuropathy and head trauma (shear forces); compression by intracranial aneurysms; infection, tumor, venous thrombosis, herniation of medial temporal lobe
|
|
what aneurysms tend to affect CN III
|
jxn of Pcomm with internal carotid; less common = jxn Pcomm and PCA, basilar & PCA jxn, or basilar & SCA jxn
|
|
what do aneurysms classically cause
|
painful oculomotor palsy that involves the pupil; may be subtle or complete
|
|
what is complete oculomotor palsy that spares the pupil usually caused by
|
diabetes
|
|
trochlear nerve palsy
|
vertical diplopia (normally causes depression and intorsion of eye)
|
|
how do ppl with trochlear nerve palsy compensate
|
looking up (chin tuck) and tilting head away from affected eye (compensate for hypertropia and extorsion)
|
|
when is depressing action of superior oblique most pronounced
|
when eye is adducted
|
|
head movement and eye abnormalities
|
moves in same direction normally served by the affected muscle
|
|
causes of vertical diplopia
|
trochlear nerve palsy, myasthenia gravis, lesions of superior division of CN III (superior rectus), and skew deviation
|
|
skew deviation
|
vertical disparity in the position of the eyes of supranuclear origin; relatively constant in all positions of gaze (unlike trochlear palsy)
|
|
what can cause skew deviation
|
lesions of cerebellum, brainstem, or inner ear
|
|
causes of head tilt
|
trochlear palsy, cerebellar lesions, meningitis, incipient tonsillar herniation, and torticollis
|
|
diplopia in abducens nerve lesions
|
horizontal diplopia; sometimes estropia present
|
|
what is abducens palsy an important early sign of and why
|
supratentorial or infratentorial tumors, pseudotumor cerebri, hydrocephalus, and other intracranial lesions; due to susceptibility of injury from downward traction caused by elevated ICP
|
|
gaze palsy
|
movements of both eyes in one direction are decreased
|
|
causes of horizontal diplopia
|
abducens palsy, myasthenia gravis, disorders of extraocular muscles
|
|
location of edinger-westphal nuclei
|
just dorsal and anterior to the oculomotor nuclei near midline
|
|
where do preganglionic parasympathetic fibers travel bilaterally from the edinger-westphal nuclei to
|
go via oculomotor nerves to reach ciliary ganglia in orbit
|
|
3 components of accomodation response
|
pupillary constriction, accomodation of lens ciliary muscle, and convergence of the eyes
|
|
what occurs when the ciliary muscle contracts
|
causes suspensory ligament to relax producing a rounder, more convex lens shape
|
|
where does the descending sympathetic pathway activate preganglionic sympathetic neurons involved with pupil dilation
|
intermediolateral cell column of upper thoracic cord
|
|
how do preganglionic sympathetic neurons of pupil dilation get to pupil
|
exit spinal cord via ventral roots of T1-2 and join paravetebral sympathetic vhain via white rami communicantes; synapse in superior cervical ganglion and ascend through carotid plexus along wals of internal carotid artery
|
|
anisocoria
|
pupillary asymmetry
|
|
classic horner's syndrome
|
ptosis, miosis, and anhidrosis along with several other minor abnormalities; due to disruption of sympathetic pathways
|
|
anisocoria in oculomotor vs horner's
|
horner's more obvious in dark, oculomotor more in ambient light
|
|
horners and light reflexes
|
still has direct and consensual response to light; dilation lag relative to normal pupil when light removed
|
|
ciliospinal reflex
|
painful pinch to neck activates sympathetic outflow, causing pupillary dilation on normal side but not on side with Horner's syndrome
|
|
anhidrosis
|
decreased sweating of ipsilateral face and neck in horner's; skin feels smoother due to decreased moisture
|
|
posible locations for Horner's syndrome lesions
|
1) lateral brainstem 2) spinal cord 3) T1-2 roots 4) sympathetic chain 5) carotid plexus 6) cavernous sinus 7) orbit
|
|
pontine pupils
|
both pupils and small but reactive to light; probably caused by bilateral disruption of descending sympathetic pathways
|
|
Afferent Pupillary Defect (Marcus Gunn Pupil)
|
direct response to light in affected eye is decreased or absent while consensual response of affected eye in opposite eye is normal
|
|
where are lesions located in Marcus Gunn pupil
|
lesions in front of optic chiasm
|
|
hippus
|
normal brief oscillation of pupil size that sometimes occurs in response to light
|
|
opiates and pupils
|
bilateral pinpoint pupils
|
|
barbituate OD pupils
|
bilateral small pupils, mimickng pontine lesions
|
|
anticholinergic agents affecting muscarinic receptors (atropine or scopolamine) and pupils
|
dilated pupils
|
|
pilocarpine eyedrops are useful when what is suspected
|
anticholinergic agents; cause pupillary constriction in parasympathetic lesions, but can't overcome pharm muscarinic blockade
|
|
light-near dissociation
|
pupils constrict much less in response to light than to accomodation
|
|
example of light-near dissociation
|
Argyll Robertson pupil associated with neurosyphilis (pupils small and irregular as well); diabetes, Adie's myotonic pupil, Parinaud's syndrome
|
|
Adie's myotonic pupil
|
degeneration of the ciliary ganglion or postganglionic parasympathetic neurons resulting in mid-dilated pupil that reacts poorly to light
|
|
Midbrain Corectopia
|
pupil assumes irregular, odd-center shape; rare
|
|
muscle of eye closure
|
orbicularis oculi (CN VII)
|
|
ptosis vs facial muscle weakness
|
ptosis upper lid comes down further over iris in affected eye; facial weakness palpebral fissure widened due to sagging of lower lid
|
|
what does cavernous sinus drain
|
eye, superficial cortex
|
|
what layer does the cavernous sinus lye
|
btwn periosteal and dural layers of dura mater-like the other venous sinuses
|
|
nerve closest to carotid in cavernous sinus
|
abducens (III, IV, and V1 also in sinus)
|
|
what nerve skirts the lower portion of the cavernous sinus and often runs through it for a short distance
|
V2-exits via forament rotundum
|
|
orbital apex
|
region where nearly all nerves, arteries, veins or orbit converge b4 communicating with intracranial cavity via optic canal and superior orbital fissure
|
|
orbital apex vs cavernous sinus lesions
|
same deficits, but more likely to involve CN II also
|
|
saccades
|
rapid eye movements reaching velocities up to 700 degrees per second; fxn to bring tagets of interest into field of view
|
|
vision during saccade
|
transiently suppressed
|
|
smooth pursuit eye movements
|
not under voluntary control; reach velocities of 100 degrees/s; allow stable viewing of moving objects
|
|
vergence eye movements
|
maintain fused fixation by both eyes as targets toward or away from viewer; velocity ~20 degrees/s
|
|
reflex eye movement examples
|
optokinetic nystagmus and vestibulo-ocular reflex
|
|
nystagmus
|
rhythmic form of reflex eye movements composed of slow eye movements in one direction interrupted repeatedly by fast saccadelike eye movements in opposite direction
|
|
what interconnects the oculomotor, trochlear, abducens, and vestibular nuclei
|
medial longitudinal fasciculus (MLF)
|
|
abducens nucleus fxns as
|
horizontal gaze center controlling horizontal movement of both eyes in direction ipsilateral to side of nucleus (some fibers project to ipsilateral lateral rectus and some to contralateral oculomotor nucleus)
|
|
paramedian pontine reticular formation (PPRF)
|
horizontal gaze center; provides input from cortex and other pathways to abducens nucleus
|
|
lesion of abducens nucleus causes
|
ipsilateral gaze palsy involving both eyes because of connections through MLF
|
|
lesions of MLF and horizontal eye movements
|
interrupt input to medial rectus; eye ipsilateral to lesion does not fully adduct on attempted horizontal gaze, also nystagmus of opposite eye (unknown reason)
|
|
internuclear ophthalmoplegia (INO)
|
classic neurologic syndrome produced by MLF lesion
|
|
where are brainstem centers for vertical eye movements
|
rostral midbrain reticular formation and pretectal area; ventral portion=downgaze and dorsal = upgaze
|
|
nucleus for downgaze
|
rostral interstitial nucleus of MLF; also Darkschewitsch and interstitial nucleus of Cajal
|
|
what controls vergence
|
descending inputs from visual pathways in occipital and parietal cortex
|
|
Parinaud's syndrome cause
|
constellation of eye abnormalities usually seen with lesions compressing the dorsal midbrain and pretectal area
|
|
Parinaud's syndrome 4 components
|
1) impairment of vertical gaze, especially upgaze 2) large, irregular pupils that don't react to light 3) eyelid abnormalities 4) impaired convergence and sometimes convergence-retraction nystagmus
|
|
most common cause of Parinaud's
|
pineal region tumors and hydrocephalus
|
|
hydrocephalus and eyes in kids
|
bilateral setting-sun sign; eyes deviate inward due to bilateral 6th verve palsies and downward due to Parinaud's syndrome
|
|
frontal eye fields
|
generate saccades in contralateral direction via connections to contralateral PPRF
|
|
parieto-occipito-temporal cortex and eye movements
|
smooth pursuit in ipsilateral direction via connections with vestibular nuclei, cerebellym, and PPRF
|
|
optokinetic nystagmus (OKN) is elicited how
|
moving a thick ribbon with vertical stripes horizontally in front of the eyes; eyes alternate btwn smooth persuit and saccades
|
|
slow phase of OKN is mediated by
|
ipsilateral posterior cortex with connections to vestibular nuclei and flocculonodular lobe of cerebellum projecting to PPRF and abducens nuclei
|
|
fast phase of OKN is mediated by
|
frontal eye fields projecting to contralateral PPRF
|
|
vestibulo-ocular reflex (VOR)
|
stabilizes eyes on the visual image during head and body movements
|
|
how is VOR tested
|
oculocephalic maneuver or cold water calorics
|