Spontaneous nystagmus in normal subjects.

We investigated the incidence of spontaneous nystagmus in 30 normal volunteers using electronystagmography (ENG). In all subjects, ENG was performed with the eyes open in the primary position, with the eyes closed, and with the eyes open in total darkness. Spontaneous nystagmus was detected in 5 (16.7%) of 30 subjects. In 15 subjects who underwent 2 ENG examinations, 4 subjects (26.7%) exhibited spontaneous nystagmus. Caloric testing was performed in 26 of 30 subjects. Spontaneous nystagmus was detected in 3 subjects who had a right-left difference in caloric response of over 40%, and in 2 of 23 subjects who had a difference of less than 40%. Our results showed that spontaneous nystagmus was detected in more subjects when the ENG examinations were repeated. Thus, a single ENG examination cannot exclude the possibility of spontaneous nystagmus.