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Classification

• Lateral nystagmus
• Vertical Nystagmus

Definition

a.k.a. Square-wave jerks

• Clinical sign of Oscillopsia, Vertigo
• Jerky nystagmus → Has 2 phases
  • Fast (saccadic) phase = defines the direction (X) of ‘X-beating nystagmus’, get exaggerated when looking toward X side
  • Slow phase = opposite direction, the ‘recovery’
• Pendular nystagmus → 2 slow phases
  • Uncommon
  • The most common causes of acquired pendular nystagmus include demyelinating disorders such as MS - Multiple Sclerosis and the syndrome of ocular palatal tremor.

Anatomy

Central vs Peripheral

Central vs. Peripheral only Based on Nystagmas. Unknown reliability of the source

• *NOTE:
  • Both eyes are affected
  • Alexander's law indicates that nystagmus will be fast beating to towards the contralateral side and slow beating to the ipsilateral side of the lesioned nerve in peripheral cause
  • Nystagmus will always be worse when you look toward the beating
    • Peripheral: only left beating /only right beating
      • i.e. the fast (saccade) phase is:
        • exaggerated when I look left
        • normal/non-existing when I look right
        • = left AND right beating nystagmus
      • → Indicate a lesion on the right vestibular nerve
    • Central: can be left beating and right beating at the same time, can be up and down and torsion ****
      • i.e. the fast (saccade) phase is:
        • exaggerated when I look left
        • exaggerated when I look right
        • = left AND right beating nystagmus
      • → Indicate a lesion in the brain