VN - Eyes Move When They Shouldn’t I: Evaluation - Week 7

Question 1

If a patient presents with oscillopsia, what are 6 things you want to find out (not history questions)?

Answer 1

What do the eyes do in primary gaze
Effect of disrupting fixation
Effects of convergence
Effects of monocular occlusion
Results of oculomotility
Associated clinical findings

Question 2

What would you suspect if a patient presents with eyes that keep moving and is asymptomatic?

Answer 2

If the patients eyes are moving and has no visual symptoms, it is almost certainly a congenital form of nystagmus

Question 3

Are congenital forms of nystagmus sinister or benign? Does it require urgent treatment? What about acquired nystagmus?

Answer 3

Benign and self-limited

Acquired forms may indicate presence of a potentially fatal condition

Question 4

Define oscillopsia.

Answer 4

Perceived motion of surrounding, stationary world

Question 5

List 9 questions to help evaluate oscillopsia.

Answer 5

What does the patient notice?
Does the world seem to move up-down/side-side or rotate?
Does it affect one or both eyes?
When did it start?
Precipitating factors?
Does it happen at rest or with movement?
Does it occur only in a particular position?
Constant or intermittent?
-how long do episodes last?
Getting better, worse, or the same?

Question 6

In a patient with oscillopsia, when you ask what a patient notices with their vision, what is it important to do?

Answer 6

Ask this question again in each gaze during oculomotility

Question 7

What is superior oblique myokymia? Describe what causes it and why. What kind of oscillopsia does it cause? What artery can cause compression of the nerve and what is a result of this?

Answer 7

An inherently monocular oscillation
Superior oblique may start twitching
Likely due to vascular compression of the 4th nerve root
Causes monocular torsional oscillopsia
Nerve can be compressed by the medial superior cerbellar artery
-pulsatile compression may damage the myelin sheath, leading to mis-transmission of nerve impulses

Question 8

List 6 drugs that may be used to treat superior oblique myokymia. Are surgical options available?

Answer 8

Oxcarbamazine
-better tolerated vs carba
Carbamazepine
Propanolol
Timonal
-eyedrop
Neurontin
Memantine
Surgical decompression may be beneficial

Question 9

What can nystagmus due to multiple sclerosis be exacerbated by and what happens as a result?

Answer 9

If exacerbated by heat, increased nystagmus may lead to worse visual symptoms

Question 10

When will a purely gaze-evoked nystagmus evoke oscillopsia and what would precipitate the nystagmus?

Answer 10

A purely gaze-evoked nystagmus will only evoke oscillopsia when refixation away from primary position brings it on
-gaze position is a precipitating factor

Question 11

What forms of nystagmus has head position as a precipitating factor? What accompanying symptom would send them to a GP/ENT rather than an optometrist?

Answer 11

Some forms of vestibular nystagmus

-accompanying vertigo

Question 12

Describe how loss of the VOR can cause oscillopsia.

Answer 12

Absence of compensatory eye movements results in any head movements taking the eyes with it and causes disturbing motion of the visual environment

Question 13

Describe whether or not treatment for oscillopsia-inducing nystagmus needs to be 100% effective or not. Note the rough rule of thumb for this.

Answer 13

Perfect gaze stabilisation isnt necessary or possible
-fluctuation even in normals
Treatment doesnt need to be 100% effective
-getting slip of image across the retina below 5 degrees/s is enough

Question 14

What are saccadic oscillations always initiated by?

Answer 14

Saccades

Question 15

What are all forms of nystagmus initiated by? What returns gaze to the desired position?

Answer 15

Slow eye movement

-saccades return gaze to desired position (if saccades are present)

Question 16

List the two major nystagmus waveform categories. One of these has three sub-categories. Note them.

Answer 16

Jerk
-linear
-decreasing velocity
-increasing velocity
Pendular

Question 17

What do linear nystagmus waveforms arise from? Generally what region of the nervous system?

Answer 17

Arises from tonic imbalance

-generally vesibular, either central or peripheral

Question 18

What do decreasing velocity nystagmus waveforms arise from, what causes this, and how does it affect eye movement? Lesions in what three areas of the brain may cause this? What type of nystagmus is it also seen in?

Answer 18

Lack of a step in a pulse-step
-leaky integrator
Eyes drift back centrally
Seen with cerebellar, brainste, or cortical lesions
Also seen in latent/manifest latent nystagmus

Question 19

What do increasing velocity nystagmus waveforms arise from? What is the cause if horizontal? What about vertical (2)?

Answer 19

Unstable integrator
If horizontal, it is congenital
If vertical, either congenital or acquired

Question 20

Describe how gaze-evoked and rebound nystagmus occurs. Note which waveform is present (3).

Answer 20

Decreasing velocity slow phases arise from mismatch between correctly programmed pulse and inadequate step
The drift towards centre reflects dynamics of the oculomotor structures
Rebound nystagmus arises when sustained lateral gaze resets the brains idea of where straight is

Question 21

Briefly describe acquired periodic alternating nystagmus and what it arises from.

Answer 21

A nystagmus that reverses roughly every 90 seconds

Appears to arise from defects in cerebellar component of long-term vestibular adaptive mechanism

Question 22

What is downbeat nystagmus a classic sign of (3)?

Answer 22

Cerebellar disease
Drug intoxication
Midbrain damage

Question 23

What can oculopalatal trmor occur in (2)? What is it?

Answer 23

Seen in MS or other disorders affecting the medulla

Eyes and soft palate oscillate in unison

Question 24

Can some oscillations consist slely of saccades? Explain.

Answer 24

Nystagmus always requires some slow movement to initiate it
Some oscillations can consist solely of saccades
-can not be described as saccadic nystagmus
-called saccadic oscillations

Question 25

True or false

Square wave jerks are never seen in normals

Answer 25

False

Almost everyone has them occasionally

Question 26

In who are square wave jerks more likely (3)?

Answer 26

Elderly

Cerebellar or cerebral disease

Question 27

What is a square wave oscillation? What is it seen in (2)?

Answer 27

Sustained square wave jerk

-seen in PSP and parkinsons

Question 28

What are microsaccadic oscillations notable for? What may it be a sign of?

Answer 28

Overshooting intended target

-may be a sign of dorsal cerebellar disease

Question 29

What is psychogenic flutter and what frequency may it exceed?

Answer 29

Voluntary nystagmus
Also back to back saccades which look pendular
Requency may exceed 20Hz