Causes of Diplopia

Question 1

A patient presents with a left hyper, what is the compensating vergence in the left eye, and what prism direction measures the vergence?

Answer 1

infravergence

BU

Question 2

how to tell what is cause a vertical deviation

Answer 2

parks three step

1. which eye has the hyper
2. is the diplopia worse on right or left gaze?
3. is it worse on right or left head tilt

Question 3

CN4 palsy

Answer 3

CN4 innervates the SO to produce incyclotorsion, depression, and abduction. A patient with a CN4 palsy will thus have restricted eye movements on depression during adduction , as this direction of gaze is when the SO is the primary depressor muscle of the eye. Patients will present with a head tilt to the opposite shoulder, the face turned away from the involved side, and the chin down in order to minimize diplopia

Question 4

what nerve is most susceptible to trauma

Answer 4

CN4
exits the dorsal midbrain
the thinnest
longest course

Question 5

diffDx for vertical diplopia

Answer 5

• browns syndrome
• skew deviation (vertical and torsional component, due to supra nuclear disturbance)
• CN 3 palsy
• orbital disease
• GRaves
• ocular MG

Question 6

Browns Syndrome

Answer 6

SO tendon sheath syndrome
affects the SO muscle but it is NOT due to an issue with CN4. It is caused by an abnormality of the SO muscle, tendon, or the trochlea, which results in restriction of the SO. The eye will be slightly depressed in primary gaze with limited elevation when the eye is adducted. Patients may develop a chin up posture in order to minimize diplopia. This condition is almost always unilateral

Question 7

most common cause of CN4 palsy

Answer 7

trauma and congenital

Question 8

diff between congenital and acquired CN 4 palsy

Answer 8

congenital will have large vertical ranges (10-15PD) and often have a longstanding head tilt. they may decompensate in the 5th to 6th decade and present with sudden onset vertical diplopia

Question 9

treatment for vertical imbalance

Answer 9

prism

• RX the associated vertical phoria measured with fixation disparity testing
• balance the vertical vergence break values ((BD break)-(BU break))/2)=correcting prism (+ answer indicates BD, - answer indicates BU)

Question 10

most common oculomotor nerve palsy

Answer 10

CN 6

-head turn towards affected side.

Question 11

the most common cause of an isolated CN 6 palsy in a patient >40y with cardiovascular conditions

Answer 11

microvascular/ischemic infarct. The palsy should resolve within 3 months. If not, an MRI and MRA should be performed

Question 12

indications for immediate imaging with an MRI and MRA

Answer 12

CN palsy in a child
multiple CN palsies
CN palsy with other neurological symptoms (headache)
pupil involving CN3 palsy

Question 13

DiffDx for CN6 palsy

Answer 13

• type 1 Duanes
• medial wall orbital blow out fracture
• decompensated congenital EP
• ocular MG
• Graves

Question 14

lateral rectus

Answer 14

abduction

Question 15

medial rectus

Answer 15

adduction

Question 16

SR

Answer 16

elevation, intorsion, adduction

Question 17

IR

Answer 17

depression, extorsion, adduction

Question 18

SO

Answer 18

incyclotorsion, depression, abduction

Question 19

IO

Answer 19

excyclotorsion, elevation, abduction