B7.033 Prework 1: Autonomic Control of Pupils

Question 1

direct response

Answer 1

response of pupil with the light shining into it

Question 2

consensual response

Answer 2

response of opposing pupil with stimulus

Question 3

discuss the pathways through the brain that allows for pupillary consensual response

Answer 3

1. optic nerve (CN II) receives light information
2. nasal retinal fibers cross in the chiasm
3. synapse of some CN II fibers in the tectum region
4. interneuron between tectum region and Edinger Westphal nucleus
5. CN III exits from Edinger- Westphal nucleus
6. CN III synapses in ciliary ganglion
7. ciliary ganglion cells work on the pupillary constrictor muscle

Question 4

pupil constrictor system

Answer 4

cholinergic neurons
muscarinic receptor
parasympathetic

Question 5

internal ophthalmoplegia

Answer 5

internal = pupil issue
anisocoria (unequal pupil size)
mydriasis
focal abnormality along CN III
no direct or consensual constriction in affected eye

Question 6

causes of internal ophthalmoplegia

Answer 6

brainstem herniation
midbrain lesion
aneurysm (PCA)
ciliary ganglion degeneration (tonic pupil)
thermal injury to short ciliary nerves
pharmacologic blockade

Question 7

symptoms of herniation

Answer 7

lateral mass pressing on brain

usually not subtle, intense symptoms like nausea, vomiting, pain

Question 8

additional symptoms of a possible midbrain lesion

Answer 8

contralateral numbness/ weakness

Question 9

how to localize a parasympathetic lesion with pharmacology

Answer 9

instill 2.5% methacholine

• post ganglionic lesion will show a pupil constriction
• pre-ganglionic lesion will not react

Question 10

why does the 2.5% methacholine test work

Answer 10

muscarinic agonist
post ganglionic lesions undergo denervation hypersensitivity over time and will be very sensitive to ACh
has to be chronic - smooth muscle makes more receptors that spread over muscle

Question 11

how to detect anisocoria due to pharmacologic blockade

Answer 11

1% pilocarpine
cannot overcome blockade
patients have no other symptoms

Question 12

stimuli for pupillary dilation

Answer 12

fear
anger
pain
arousal

Question 13

describe the orientation of the sympathetic system controlling the eye

Answer 13

starts in hypothalamus
descends to T1-T2 level of spinal cord and synapses
enters sympathetic chain and travels up to superior cervical ganglion
synapses and exits ganglion
fibers to the eye travel alongside the internal carotid

Question 14

sudomotor fibers to the face

Answer 14

follow the external carotid

Question 15

characteristics of pupil dilator muscle

Answer 15

noradrenergic neurons
a1 receptors
sympathetic innervation

Question 16

Horner’s syndrome

Answer 16

anisocoria: miosis in 1 eye
ptosis
anhidrosis

Question 17

causes of Horner’s syndrome

Answer 17

brainstem strokes (lateral medulla)
MS
syringomyelia
Pancoast tumor (apical lung)
thyroid carcinoma
carotid artery aneurysm

Question 18

localizing pre- vs post- ganglionic sympathetic lesions

Answer 18

postganglionic: will NOT react to cocaine, will react to adrenaline 1:1000
preganglionic: will react to cocaine, will NOT react to adrenaline 1:1000

Question 19

how does the 4% cocaine test work

Answer 19

cocaine increases action of NE by inhibiting amine oxidase
in post ganglionic lesions, AO is depleted so cocaine has no effect
in normal pupil and pre ganglionic lesion, pupil will dilate

Question 20

how does the adrenaline 1:1000 test work

Answer 20

post ganglionic will markedly dilate because adrenaline is not destroyed by amine oxidase
pre ganglionic will not react because amine oxidase is still present and will break down adrenaline