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Cranial Nerves
 
 

Nystagmus

 
 
 
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Overview

The term nystagmus is used mainly to refer to jerk nystagmus, abnormal rhythmic eye movements that may occur due to peripheral nervous system, central nervous system or vestibular pathology.

Jerk Nystagmus

  • How to Perform

  • Ask the patient to look at your finger, held ~50cm in front of their eyes (in primary position). Repeat in the extremes of left and right lateral gaze, as well as in superior and inferior gaze.
  • Look For

  • Slow drifting movements of the eye interspersed with corrective fast saccadic movements. Note whether these movements are horizontal, vertical or torsional.
The direction of the nystagmus is described as the direction of the fast-beating movement.
  • Interpretation

  • Physiologic nystagmus - a few beats of horisontal nystagmus at the extremes of lateral gaze
  • Positional nystagmus - transient (<1min) of horisontal nystagmus following positional changeA sign of benign paroxysmal positional vertigo
  • Upbeat nystagmus - downward slow movements with upward fast movements in primary positionSuggestive of cerebellar or brainstem disease
  • Downbeat nystagmus - upward slow movements with downward fast movementsClassically occurs in the setting of pathology affecting the central pathway
  • Causes of Jerk Nystagmus

  • Physiologic
  • Congenital
  • Central (brainstem / cerebellum) - multiple sclerosis, stroke, trauma, tumour
  • Visual impairment - intra-ocular, optic nerve (II), total blindness
  • Vestibular disturbance - Meniere’s, benign paroxysmal positional vertigo, labyrinthitis
  • Drugs - alcohol, sedatives, phenytoin

Pendular Nystagmus

Pendular nystagmus is less common, and manifests as equal movement to both sides (i.e. no fast or slow phase).
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