Convergence nystagmus

Abstract

Five patients with convergence nystagmus were examined. Four of them suffered from pinealoma, and one probably from atypical Fisher syndrome. Fast phases of the convergence nystagmus were fast adducting movement in four patients. In the other patient, the fast phase of the nystagmus was an adducting movement the velocity of which was expressed by a decaying exponential curve. The velocity of these phases was a little slower than that of the adducting saccade in four patients and the same in one patient. Almost all fast phases were accompanied by upward movements. Slow phases of the nystagmus consisted of abducting movement which showed a velocity with a decaying exponential curve, the time constant of which was 0.1 or 0.2 second. These eye movements were identical to the associated involuntary adducting movement during vertical saccades found in normal subjects. It is suggested that the disordered nervous system which should regulate the excitability of various neurons for eye movement is responsible for convergence nystagmus.

Key Words:

• convergence nystagmus
• adducting saccade
• adducting movement associated with vertical sac-cade