Abstract
A 20-year-old male had alternating nystagmus and no other abnormal neurological findings. The nystagmus was generally left-beating, and almost jerking. The mean velocity of the slow phase was 65°/second, with the mean frequency was 4.2 Hz. The optokinetic pattern was the inverted type. Caloric responses were brisk. The nystagmus sometimes turned spontaneously into the alternating type. Although the amplitude and frequency of alternating nystagmus was not “crescendo and decrescendo”, the alternating cycle was nearly stable and the average duration of nystagmus in either direction was typical (about 110second). Moreover alternating nystagmus was induced by smooth pursuit eye movement. We considered that alternating nystagmus in this patient was induced by a modification of the vestibulo-ocular reflex caused by smooth pursuit eye movement.
