Eye movements and underlying neural pathology

Question 1

lateral rectus LR 6 abducens

Answer 1

looks out or laterally.

Below is it’s palsy.

Question 2

How to manage a patient who has a pupil sparing third nerve palsy?

Answer 2

Observation or supportive care for pts who have vasculopathic risk factors (should improve in 6-12 weeks) but can get imaging to rule out mass or aneurysm.

Pupil sparing third nerve palsy is from microvascular ischemia (diabetic ophthalmoplegia)

Question 3

Aneurysmal compression of oculomotor nerve

Answer 3

injury to CN3 can happen anywhere along length from brainstem to orbit. Parasympathetic fibers control pupillary constriction (control sphincter papillae muscle) and they run outside of the 3rd nerve fascicle. Less susceptible to ischemia but are affected by extrinsic mass.

non pupil sparing third nerve palsies are caused by MASS EFFECT (tumor intracranial aneurysm) and so can have dilated pupils.

Question 5

diabetic ophthalmoplegia

Answer 5

injury to CN3 can happen anywhere along length from brainstem to orbit. Parasympathetic fibers control pupillary constriction (control sphincter papillae muscle) and they run outside of the 3rd nerve fascicle. Less susceptible to ischemia but are affected by extrinsic mass.

So pupil sparing 3rd nerve palsies are caused by microvascular ischemia.

See this effect with diabetes, HTN, and HLD and advanced age.

Question 7

what test to order after see a non pupil sparing third nerve palsy on physical exam?

Answer 7

need to get a MRA or CT angiography for the pt

Until proven otherwise a non pupil sparing or a dilated single pupil (non reactive to light) is from an aneurysm or mass.

Question 8

CN4 does what

Answer 8

looks down and out

superior oblique (SO) 4 trochlear nerve

Question 9

Oculomotor CN3 does what?

Answer 9

it does all other movements

also raises the eyelid.

Question 10

lacteral rectus abducents palsy?

Answer 10

likely from DM2 ophthalmoplegia so treat diabetes

Question 11

bilateral lateral rectus or abducents nerve palsy need to consider

Answer 11

increased cranial pressure

do a CT scan to rule out ICH

if negative do an a MRV to look for vein thrombosis

Question 12

pt presents with R ptosis and L is dilated and R pupil is non constricted this is:

Answer 12

oculomotor nerve palsy of R eye

see ptosis = affected eye. So know that L eye is normal.

This is due to diabetic opthalmoplegia with central infarction of the nerve.

Question 13

pt presents wtih ptosis of left eye and constricted left eye and dilated right eye. smoker. Also see drooping of left eye and some drooping of mouth.

Answer 13

This pt has compression of LEFT sympathetic chain.

Sympathetic chain controls eyelid and dilation of pupil. Pt has pancoast tumor that is compressing on the sympathetic chain on LEFT side.

Need to get CT angio to rule out carotid dissection (will have hx of trauma, MVA) or pancoast tumor.

Question 14

pt has ptosis of left eye and dilated right pupil. also has out and down position of left eye.

Answer 14

this is a berry aneurysm of posterior communicating artery of the left eye.

See ptosis and dilated pupil as there’s aneurysmal compression of the outside nerve fiber of the CN3 which controls constriction and so it’s left pupil is dilated. Also see CN3 palsy because of compression.

happens with 7mm aneurysm of posterior communicating artery.