Nystagmus

Question 1

What is nystagmus?

Answer 1

Involuntary oscillations of the eye initiated by slow eye movements

Question 2

What are the characteristics of nystagmus?

Answer 2

constant vs intermittent
pendular vs jerk
horizontal vs vertical
conjugate vs disconjugate

Question 3

What are different form of nystagmus?

Answer 3

• upbeat nystagmus
• jerk nystagmus, fast phase upwards
• jerk nystagmus, fast phase downward
• see-saw nystagmus
• one eye rises/while other falls
• pendular nystagmus

Question 4

What is a null point?

Answer 4

position at which amplitude and frequency of nystagmus is least visible

Question 5

What is the neutral point?

Answer 5

position at which symmetrical jerk nystagmus changes direction

Question 6

What is the vision like with nystagmus?

Answer 6

nystagmus moves items of interest off the fovea causing a reduction in vision

Question 7

What are associated symptoms of Nystagmus?

Answer 7

• oscillopsia
• sense of the world moving/spinning
• vertigo
• dizziness
• ataxia (balance/speech)
• lack of motor co-ordination

Question 8

What are the names of normal nystagmus?

Answer 8

• Optokinetic nystagmus
• Vestibulo-ocular reflex
• End point nystagmus

Question 9

What is OKN nystagmus ?

Answer 9

• This is normal physiological form
• a physiologic phenomenon produced by asking the patient to visually track a succession of moving stimuli.

Question 10

What is the cause of OKN nystagmus?

Answer 10

jerk nystagmus caused by patterned targets moving rhythmically across the visual field

Question 11

What is the mechanism for VOR?

Answer 11

• Producing eye movements that counter head movements
• ensures best vision during head motion by moving the eyes contrary to the head to stabilize the line of sight in space.

Question 12

What happens with VOR?

Answer 12

e.g. left rotation of the head triggers activity in the left horizontal canal and excites neurons in the left vestibular nucleus, resulting in reflexive eye movements to the right

Question 13

What is end-point nystagmus?

Answer 13

very small amplitude jerk nystagmus in extreme gaze positions

Question 14

What is vestibular nystagmus?

Answer 14

Can be due to an imbalance somewhere in the vestibular pathway
- can be peripherally in the canals or centrally in their brain pathway

Question 15

How can you check for peripheral vestibular nystagmus?

Answer 15

By removing fixation - fresnel glasses or cover fixating eye during ophthalmoscopy

Question 16

What are the causes of acquired pendular nystagmus?

Answer 16

• visual loss
• disorders of myelin/optic nerve
• whipple’s disease
• acute brainstem stroke

Question 17

When does infantile nystagmus start ?

Answer 17

usually begins in the 1st month of life
- waveforms can change in early infancy, usually stable by 4 yo

Question 18

What are the common findings of infantile nystagmus?

Answer 18

• conjugate
• usually horizontal
• +ve FH both autosomal dominant and sex-linked recessive
• decreases with convergence or relaxation
• has null/neutral point in different directions of gaze

Question 19

What is the workup for nystagmus?

Answer 19

VA
colour vision
pupils - look for iris illumination
VF
Fixation stability, central and in diff gazes
compare movement in both eyes (stare at bridge)
occlude each eye to check for latent