Thursday, 4 November 2010

MRCP revision battle 42.5: Nystagmus

Nystagmus is involuntary, jerky eye movements.  

Nystagmus at the extremes of gaze is normal.

Horizontal nystagmus may be due to:
  • vestibular lesions - acutely the nystagmus is away from the affected side
  • cerebellar lesions - tends to be fast nystagmus and towards the affected side
  • MS - suspect if nystagmus is more in the eye which is abducting
  • benign positional vertigo - suspect if nystagmus varies with head position
  • peripheral lesion - suspect if also tinnitus/other signs

Down beat nystagmus is associated with:
  • Arnold Chiari malformations
  • Syringobulbia  (not sure what these are? revise battle 11.3!)

Upbeat nystagmus is associated with:
  • cerebellar vermis lesions
  • organophosphate poisoning

Sticking with eyes we're now going to consider miosis....