Iris & Pupil Neuro Flashcards
Iris
- layer containing nerves
- which nerves and types
Stroma
LPCNs = sensory, SNS SPCNs = PNS, sensory, SNS
Iris
- which layer contains sphincter muscle
- innervation of sphincter muscle
Stroma
CN3 PNS via SPCNs
Iris
- which layer contains dilator muscle
- innervation of dilator muscle
Anterior epithelium
SNS via SPCNs and LPCNs
Pupillary disorders
-aniridia
—describe
—assoc condns (3)
Hypoplastic iris -> large pupillary opening
Cataracts, glaucoma, vision impairment from macular/ON hypoplasia
Pupillary disorders -ectopia lentis et papillae —describe —assoc condns (5) —other ocular signs (3)
Rare AR
Bilaterally displaced pupil - usually inferotemporally
Lens dislocation in opposite direction
Severe axial myopia, RD, large corneal diameter, cataract, abnormal transillumination
Microspherophakia, miosis, poor dilation with mydriatics
Pupillary disorders
-ectopic pupils
—describe
Idiopathic tractional = fibrous structure tethers the margin to peripheral cornea
May be inherited as isolated ocular finding
Pupillary disorders -coloboma —describe —possible accompanying ocular sign —causes (3)
Inferior/inferior-nasal notch
Chorioretinal/ON colobomas
Isolation (healthy indiv)
Chromosomal duplication/deletion
Complex congenital disorders (e.g. CHARGE)
Pupillary disorders
-persistent pupillary membrane
—describe
Spoke-like opacities across pupil
Derive from tunica vasculosa lentis
Anterior chamber cleavage anomalies
- assoc with
- Peter’s
- Rieger’s
Mis-shapen pupils + abnormal adhesions between cornea and iris
P: central corneal defects
R: peripheral corneal defects
Pupillary light pathway
- afferent = __ -> __
- efferent = __
Retina -> EW nucleus
PNS pathway
Pupillary light pathway
-afferent pupillary pathway
—pupillary fibers travel __ as far as __, with nasal crossing at the chiasm
—fibers exit __ and travel within the __ to __
—fibers then travel to __, with those that cross to the opposite travelling in the __
Travel with visual fibers -> posterior optic tract
Exit posterior 1/3 of optic tract, travel within brachium of superior colliculus to pretectal nucleus and synapse
Travel to BOTH EW nuclei - those that cross to opposite nucleus travel in posterior commissure
Pupillary light pathway
-efferent pupillary pathway
—preganglionic fibers leave __ with __ and follow __ into the orbit
—PNS fibers leave and enter __
—postganglionic fibers travel with __ to anterior eye to innervate __
Leave EW nucleus (MB) with motor fibers of CN3 and follow inferior division into orbit
Leave inferior division, enter ciliary ganglion, and synapse
Travel with short ciliary nerves -> anterior eye -> sphincter and ciliary muscle (accomm)
(EW -> CN3 inferior division -> ciliary g + synapse -> short ciliaries -> sphincter, ciliary muscles)
Disruption of afferent pathway -RAPD —causes —appearance —assoc with
Optic tract lesion = contralateral APD
Also: RD, ischemic CRVO, ON ischemia or compression, optic neuritis, asymmetric glaucoma
Amaurotic/deafferented pupil
Vision loss
Disruption of afferent pathway
-pretectal pupil
—when it’s seen
—signs
Lesions affecting dorsal MB -> Parinaud syndrome
Usually bilateral, asymmetric
Upgaze paresis, head tilt
Contralateral APD + light-near dissociation
Disruption of afferent pathway
-accommodation-Convergence Reaction Pathway
—afferent
—efferent
A: retina -> EW nucleus -> striate cortex -> FEF -> CN3+EW nuclei
E: PNS pathway (EW -> CN3 inferior division -> ciliary g -> synapse -> anterior eye)
Disruption of afferent pathway -Argyll-Robertson pupil —laterality —how —pupil testing —appearance —causes
Bilateral, asymmetrical
Interrupt fibers from pretectal nucleus to PNS nucleus
Poor direct, normal consensual, light-near dissociation
Miosis evident in darkness - fibers carrying inhibitory feedback to PNS travel here (no dilation with atropine, either)
Diabetic ret, alcoholic neuropathy, neurosyphilis
Disruption of efferent pathway
-CN3 palsy/oculomotor impairment
—relationship of CN3 and PNS fibers and implications
—dilated pupil + CN3 involvement
PNS are superficial to CN3 as emerge from MB
-PNS fibers are often spared in ischemic lesions (e.g. DM), but are susceptible to compression
Highly suspicious of a compression intracranial lesion (aneurysm)
Disruption of efferent pathway -tonic pupil —site of damage —pupillary testing —other signs —diagnostic testing
Ciliary ganglion or short ciliary nerve
Poor light reponse + loss of accommodation
Decr corneal sensitivity
Administration of 1% pilocarpine (cholinergic agonist) will constrict it
Disruption of efferent pathway -Adies tonic pupil —cause —who —progression —diagnostics
Idiopathic
Women 20-40
Becomes smaller, doesn’t dilate well in dark
Significant miosis with 0.125% pilocarpine due to sphincter hypersensitivity
Disruption of efferent pathway
-tonic pupil management
—testing
—elderly pts
FTA-ABS or MHA-TP for neurosyphilis
ESR + CRP to screen for GCA in elderly
Pharmacological dilation
- gtts (4)
- others/non-drops
- a quick test
Atropine, tropicamide, cyclopentolate, phenylephrine
Scopolamine patch, ipratropium, jimson weed, blue nightshade, angels trumpet, visine/clear eyes
1% pilo will fail to dilate
Unreactive pupils
-angle-closure glaucoma
—when narrow-angle pt has emergent IOP, apply 1% pilo to incr AH outflow
False - breaks posterior synechiae, but doesn’t incr outflow
Sympathetic pathway for pupillary dilation
- SNS fibers are controlled by
- SNS innervation originates in
- preganglionic synapse
- postganglionic fibers form
Hypothalamus
T-1 thru T-3
Superior cervical ganglion
Carotid plexus around internal carotid a
Sympathetic pathway for pupillary dilation
- orbital fibers leave carotid plexus
- SNS fibers follow __ -> __ -> __
In cavernous sinus*
Follow nasociliary n -> long ciliary n -> dilator + ciliary muscles (inhibits ciliary)
*3,4,6, V1, V2 - V3 and 7 do not go thru
Horner’s
- disruption of __
- signs
Efferent/SNS dilation
Mild ptosis, facial anhidrosis, miosis
Dilation lag in dim light
Normal reaction to light and near stimuli
Horner’s -central —neuron —common cause and appearance —uncommon cause and appearance
1st order
Common = lateral medullary stroke (Wallenberg syndrome)
- Horner’s ipsilateral to lesion in 3/4 cases
- defective smooth pursuit, ataxia, torsional or horiz nystagmus
Uncommon = mesencephalic + pontine lesions
-Horner’s + contralateral CN4 palsy
Horner’s -preganglionic —neuron —common cause and appearance —less common cause
2nd order
Pancoast tumor
-ipsilateral Horner’s
Brachial plexus injury
Horner’s -postganglionic —neuron —common causes and appearance (2) —other cause
3rd order
Carotid dissection
-ipsilateral HA/pain, ocular/cerebral ischemia
-Horners ~50%
Cavernous sinus lesions
-Horners + any combo of ipsilateral CN3,4,6,V1,V2 involvement
Other: small vessel ischemia
Horner’s
-pharmacological testing
—cocaine
—hydroxyamphetamine
C: 5-10%
- constriction = no problem
- no response = problem, non-specific location
H: 1%
- no response = 3rd order neuron (postganglionic)
- dilation = 1st/2nd order neuron (preganglionic)
Horner’s
-congenital
—causes (2)
—appearance
Neuroblastoma, birth trauma
Heterochromia - normal iris pigmentation fails to develop
Pupillary disorders of other neurologic conditions
- coma
- opiates
- migraine
Structured lesion
Pinpoint
Adilated pupil + ipsilateral HA
Pupillary disorders of other neurologic conditions
-seizures
—general tonic-clonic
—epileptic focus
Bilateral mydriasis
Ictal unilateral mydriasis
Other pupillary disorders
-westphal-piltz reflex
Constriction in darkness (normal in sleep)
Other pupillary disorders
-paradoxic constriction in darkness
May suggest a retinal dystrophy (congen stationary night blindness, achromatopsia)
Other pupillary disorders
-tournays
Induced by lateral gaze
<10% of population
Pupil of abducting eye > adducting eye
Other pupillary disorders
-oculosympathetic spasm
Irritation of OS pathway -> unilateral mydriasis +/- ipilateral facial flushing, lid retraction, hyperhidrosis
Other pupillary disorders
-tadpole-shaped pupil
Episodic mydriasis with segmented distortion
Intact light constriction
Abnormal spasm of dilator
