[A case of Fisher's syndrome with upbeat nystagmus].

We reported a case of Fisher's syndrome with upbeat nystagmus. The syndrome manifested itself with the appearance of diplopia and ataxic gait preceded by cold-like symptoms. Although slight blephaloptosis, marked bilateral upward gaze palsy, and restricted abduction of the right eye were observed, light reflexes and Bell's phenomenon were normal. A slight decrease in the muscular power of the distal extremities, bilateral fingertip dysesthesia, and diminished sensation of vibration were observed. All muscle stretch reflexes were absent, and no pathologic reflexes were noted. Truncal ataxia and incoordination were observed. The cerebrospinal fluid showed albumino-cytologic dissociation. Upbeat nystagmus in five directions of gaze was recorded on the EOG, the smooth pursuit eye movement showed a staircase pattern, and dysmetria was present in the saccadic eye movement. The caloric test elicited a satisfactory response, but the visual suppression test produced poor suppression. Taken altogether, the test results suggest that the responsible lesions in this case were not only peripheral but also central, extending from the midbrain to the tegmentum pontis and the vestibulocerebellum.