交代性眼振の1症例

PERIODIC ALTERNATING NYSTAGMUS, A CASE REPORT

　I．はじめに

　開眼正中位で周期的に眼振方向が左右に変換する眼振は，交代性眼振（nystagmus alternans）と呼ばれている。この交代性眼振は眼振の解発や制御についての考察の上で興味深いものであるが，その眼振方向交代のメカニズムは不明である。

　われわれは先天性と思われる交代性眼振の1症例を経験したのでその概要を報告する。

　A woman, aged 20, with congenital periodic alternating nystagmus was studied with electronystagmography. With forward gaze the horizontal nystagmus changed its direction alternatingly within the period of 120-300 seconds. However, with the eyes fixed at certain direction or by changing the head position this nystagmus could not be elicited. When the eyes were closed the spontaneous nystagmus was markedly reduced. With stimulation of the vestibule the vestibular nystagmus was induced. This alternating nystagmus continued during the follow-up period of 1 year.