Pupils and ptosis Flashcards
Sphincter pupillae muscle:
Circular smooth muscle at inner ring of pupil.
Innervated via post ganglionic parasympathetic fibers from ciliary ganglion.
Nerves travel with CN3 to ganglion, then with short ciliary fibers of CN6
*supplied via ACh
Dilator pupillae muscle:
Single layer of myopeithelium (muscle base, epith. Apex) at pupil base.
Innervated via postganglionic sympathetic fibers from sup. Cervical ganglion.
Nerves travel with long ciliary nerves of CN6
*supplied via noradrenaline
Afferent pupil pathway:
Retinal light input > Ganglion cell axions > optic tract > split at chiasm > split before LGN > sup. Colliculus > synapse with olivary pretectal nucleus.
Afferent (retina) / Efferent (midbrain light reflex) signals processed > ipsi/contralateral Edinger Westphal > parasympathetic path.
Parasympathetic pupil pathway:
Edinger Westphal > with CN3 (accommodative axons) > cavernous sinus > synapse at ciliary ganglion > with short ciliary via subarachnoid space > iris sphincter > bilateral / equal constriction
Sympathetic pupil pathway:
1st neuron: hypothalamus > ciliospinal Centre of bulge and Waller (C8/T2)
2nd: preganglionic fibers pass stellate ganglion (lung apex) > sup. Cervical gang. (jaw)
3rd: postganglionic fibers plexus with carotid > cavernous sinus > SO fiss. With nasociliary of CN5 > long ciliary in suprachoroidal space > dilatory > mydriasis
Also innervate mullers. facial innervation splits before sup. Cervical G.
PERRLA examination (first test):
Pupils Equal Round Reactive to Light (direct/consensual) and Accommodative
1. Direct response: light activates ipsilateral EW > ipsilateral constriction
2. Consensual: light activates ipsilateral EW > contralateral EW activation > contraction
Accommodative: Near response triad > visual cortex / pupillomotor Centre in midbrain response
RAPD examination (second test):
Swinging flash test for Relative Afferent Pupil Defect.
No RAPD: equal constriction W/O radiation excluding Hippus
Mild: affected pupil constricts and redilates
Moderate: affected pupil does not change, then dilates
Severe: immediate dilation of affected pupil
Lack of consensual response is not RAPD, only examine pupil with light shown on it
Horners syndrome symptoms:
Disruption of sympathetic innervation to pupil dilator / mullers / ciliary body / facial sweat glands.
Causes Miosis / partial ptosis (1mm) / anhidrosis (not 3rd order) / accommodative excess / Conj. BV dilation
Congenital cases > Lighter/Darker Brown/Blue eyes
Causes of anisocoria:
Efferent pupil pathway dysfunction:
Physiological (EW asymmetric inhibition)
CN3 palsy
Adies tonic
Aberrant regen (CN3p / adies)
Pharmacological
Pupil damage (trauma/Sx)
AAGC
Common causes of horners syndrome:
1st : brainstem/spinal disease (vascular/tumor), diabetic neuropathy
2nd: Pancoast tumor, carotid/aortic aneurysm, neck lesion
3rd: carotid aneurysm, cavernous sinus mass, cluster headaches
CN3 palsy symptoms:
Mydriasis: Pia BV compression > pupillomotor fiber ischemia
Full ptosis: sup. Levator innervation loss
Down/out turn: Sup/Inf/medial rectus, inf. Oblique innervation loss
Thunderclap headaches
Causes of CN3 palsy:
Pupil involving: compressive lesion/aneurysm on pia BV for parasym. fibers
Pupil sparing: DM/HT > main trunk ischemia
* Giant cell arteritis (temple pain) / Pos. communicating artery aneurysm / cavernous fistula common
Myasthenia gravis imitates pupil sparing palsy
Adies tonic pupil:
Segmental denervation of post gang. Parasym. > sphincter loss > dilation and wormlike light response
Blur in affected eye with light-near dissociation (accomodative response is healthy following aberrant regen)
Caused by viral infections, usually women
Aberrant regen:
Adies: acc. Parasym. From ciliary muscle innervate iris sphincter (2 months) > light/near dissociation > reversal of anisocoria greater in dark
CN3 palsy: accom. Parasym. Regenerate denervated pupils > miosis (anisocoria reversal). Regen can come from oculomotor fibers > miosis on different gaze
Common pharmacologic mydriasis/miosis:
Tropicamide: Muscarinic antagonists > Ach receptor block > sphincter paralysis
Phenylephrine: adrenergic 1 agonist
Pilocarpine: muscarinic agonist > Ach receptor upregulation > miosis
Apraclondine: Alpha agonist > dilation (weak a1, strong a2)
Tamulosin: Alpha antagonist > adrenaline receptor block > dilator paralysis
Assessing anisocoria greater in light:
Greater in light > parasym. Loss > CN3 palsy / adies
0.1% pilocarpine > great constriction of affect pupil in early adies (<2w) from Ach upregulation
1% pilocarpine > constriction of CN3 palsy
Faliure to constrict > pharmacological/atrophic mydriasis
Assessing anisocoria greater in dark:
Greater in dark > sym. Loss > horners/aberrant regen (CN3/adies)
0.5% apreclonidine > pupil dilation of affected eye w/lid raising and constriction of normal pupil. Requires 1w post onset for a1 upregulation
1% hydroxyamphetamine > dilation of affected eye if 1/2 order neuron lesion (release of 3rd neuron noradrenaline)
Simple congenital/myopathic ptosis:
Usually unilateral, from fibrotic LPS > raised lid on downgaze + indistinct lid crease
Blepharophimosis syndrome is a type > horizontally short palpebral fissure with no LPS function
Types of ptosis:
Myogenic (MG, simple congenital, blepharophimosis)
Neurogenic (CN3, horner, marcus gunn)
Mechanical
Aponeurotic (LPS disinsertion)
Pseudooptosis
Myasthenia gravis:
Autoimmune disorder > auto antibodies against Ach receptors of striated muscle > weakness
Causes limb weakness, lack of expression, ptosis +_ diplopia worsening over the day.
Tested via 1minute upgaze, or ice pack for 2m (improves neurotransmission)
Chronic progressive external ophthalmoplegia:
Most common mitochondrial myopathy > ATP dysfunction > EOM fatigue
Progressive disease, noted in teenages
Bilateral ptosis > then leteral gaze > down gaze
Rarely causes diplopia as loss is symmetrical
Marcus Gunn Jaw winking syndrome:
Synkinetic neurogenic ptosis from CN5(V3 mandibular) anastamosis with CN3 > wink reflex on jaw contraction
Aponeurotic ptosis:
Lid disinence/redundancy > high lid crease which remains on down gaze
Measuring ptosis:
Margin reflex distance: 4mm from corneal reflex and upper lid
Palpebral fissure: difference between eyes: 2/3/4mm mild/moderate/severe
Levator function: pressure brow, measure upper lid change from downgaze and upgaze (15mm normal)
Upper lid crease: distance between lid margin and crease in downgaze (8mm normal).
physiological anisocoria:
1/3 prevelance
longstanding, <1mm discrepancy, stable in light/dark
common pharmacologic agents in pupil dilation
Scopolamine patches
nasal vasoconstrictors
antiperspirants
opioids
insecticides
clinical assessment of horners
Dilation lag of mitotic pupil in dark (5-15s) > greater anisocoria at 5s, lesser by 15.
W/ no abnormality in near response
