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4-aminopyridine restores visual ocular motor function in upbeat nystagmus


The effect of the potassium channel blocker 4-aminopyridine (4-AP) on spontaneous upbeat nystagmus (UBN) was investigated with the search coil technique during fixation in different gaze positions and smooth pursuit in a patient before and after ingestion of 10 mg 4-AP. UBN was reduced from 8.6 deg/s to 2.0 deg/s by 4-AP causing subjective relief from distressing oscillopsia, and impaired upward smooth pursuit was restored (gains: before medication 0.38; after medication 0.86). In the dark, UBN was slightly stronger and not affected by 4-AP. We propose that 4-AP improved the function of cerebellar pathways that mediate gaze holding and smooth pursuit by intensifying the excitability of cerebellar Purkinje cells.

  • 4-AP, 4-aminopyridine
  • DBN, downbeat nystagmus
  • UBN, upbeat nystagmus
  • upbeat nystagmus
  • 4-aminopyridine
  • potassium channel blocker
  • smooth pursuit
  • case report

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