Pupillary Responses

Question 1

A PICA aneurysm most commonly presents with. . .

Answer 1

. . . ipsilateral cranial nerve III palsy

Question 2

Pupillary vs occulomotor fibers of CN III

Answer 2

Remember, everything in the eye is opposite!!!

So, pupillary fibers are on the outside of CN III and occulomotor functions are on the inside of CN III

Question 3

Isolated pupillary abnormalities of CN III suggests. . .

Answer 3

. . . a compressive etiology

Question 4

Isolated occulomotor abnormalities of CN III suggests. . .

Answer 4

. . . an ischemic etiology

Question 5

Adie pupil

Answer 5

Tonic pupil with poor reaction to light but appropriate accomodaton on near gaze

It is slow to dilate after constriction.

This is due to damage of the parasympathetic ganglion or short ciliary nerves followed by aberrant reinnervation.

Specifically, idiopathic cases of tonic pupil are referred to as Adie pupil.

Question 6

The pupillary ___ muscle is innervated by the parasympathetic nervous system.

The pupillary ___ muscle is innervated by the sympathetic nervous system.

Answer 6

The pupillary sphincter muscle is innervated by the parasympathetic nervous system.

The pupillary dilator muscle is innervated by the sympathetic nervous system.

Question 7

Cell bodies for the parasympathetic, preganglionic neurons innervating the muscles of the eye are located in the ___

Answer 7

Cell bodies for the parasympathetic, preganglionic neurons innervating the muscles of the eye are located in the Edinger-Westphal nucleus

They then travel out via CN III to the ciliary ganglion.

They innervate the sphincter muscle via the short ciliary nerves.

Question 8

Cell bodies for the sympathetic, preganglionic neurons innervating the muscles of the eye are located in the ___

Answer 8

Cell bodies for the sympathetic, preganglionic neurons innervating the muscles of the eye are located in the intermediolateral gray matter of the spinal cord C8-T2

They travel up the cervical chain to the superior cervical ganglion in the distal neck. Then, postganglionic neurons travel superficially on the carotid arteries to reach the ciliary ganglion, joining the parasympathetic fibers.

They innervate the dilator muscle via the long ciliary nerves.

Question 9

A patient presents with anisocoria.

Worsening anisocoria in darkness suggests that which pupil is the abnormal one?

Answer 9

The small pupil

As the contralateral, larger pupil appropriately adjusted to darkness.

Question 10

A patient presents with anisocoria.

Worsening anisocoria in light suggests that which pupil is the abnormal one?

Answer 10

The large one

As it was unable to constrict as well as its counterpart in response to light.

Question 11

Extraocular muscle innervation by each cranial nerve (table)

Answer 11

Question 12

Triad of Horner’s syndrome

Answer 12

Ptosis, miosis, anhidrosis

Question 13

Testing in the case of suspected, but uncertain, Horner’s syndrome

Answer 13

Historically, cocaine was used. Now, apraclonidine is used.

Apraclonidine is a weak alpha 1 agonist and a strong alpha 2 agonist. In a normal pupil, alpha-1 receptors dominate, and apraclonidine has only weak activity and will cause no change in pupillary changes.

In a Horner’s syndrome pupil, sympathetic denervation causes increased expression of alpha-2 receptors, and so apraclonidine wll produce dilation of the eye and reversal of anisocoria.

Question 14

Physiologic anisocoria

Answer 14

Baseline pupillary difference of 0.4 mm or more with normal pupillary responses bilaterally

Occurs to varying degrees in ~20% of the population

Difference is due to physiologically asymmetric sympathetic innervation and is exacerbated in the dark.

Question 15

Adie syndrome

Answer 15

Tonic pupil plus hyporeflexia

Question 16

Unilateral vs bilateral Adie’s pupils

Answer 16

A unilateral Adie pupil is usually benign.

Its unilaterality and its sluggish response to light distinguish it from Argyll Robertson pupils.

Question 17

Gold standard to assess for susepcted cerebral aneurysm

Answer 17

4-vessel catheter angiogram

However, most patients will receive less invasive imaging with a CT/CT angio or MRI/MRA first

Question 18

Any third nerve palsy with ___ should be considered a medical emergency

Answer 18

Any third nerve palsy with pupillary involvement should be considered a medical emergency

Question 19

Partial third nerve palsy without pupillary involvement in an older individual (> age 50) with vascular risk factors and no other symptoms

Answer 19

Likely a microvascular ischemic lesion in the deep fibers of the third nerve

This condition almost always resolves spontaneously within 3 months and may be observed for a period of time before proceeding with imaging.

Question 20

When anisocoria is identified, what additional features can help you determine which pupil is abnormal?

Answer 20

Examination in dark and light

Presence of ptosis

Occulomotor abnormalities

Question 21

Quick sympathetic vs parasympathetic anisocoria

Answer 21

Sympathetic etiology = prominent in dark = localized to smaller pupil

Parasympathetic etiology = prominent in light = localized to larger pupil

Question 22

Single most common cause of anisocoria in all comers

Answer 22

Physiologic anisocoria