Paroxysmal alternating nystagmus.

Paroxysmal reversal of spontaneous nystagmus has rarely been described. Herein, we report recurrent bouts of vertigo and oscillopsia in association with reversed spontaneous nystagmus in a patient with prior surgical resection of the cerebellar vermis due to medulloblastoma and subsequent labyrinthine damage. The symptoms almost completely resolved with carbamazepine. The episodes may be ascribed to paroxysmal reversal of the vestibular asymmetry due to intermittent decompensation by the deficient cerebellum.