自発性垂直性眼振に関する臨床的考察

抄録

A careful analysis was made of the results of electronystagmography in 3 patients with spontaneous vertical nystagmus, and the causes of their nystagmus are discussed.
Case 1 : a 24-year-old man showed primary position upbeat nystagmus with large amplitude (4°-6°) and 2 Hz frequency, which decreased on upward gaze and increased on downward gaze. This nystagmus changed to downbeat nystagmus when convergent gaze was maintained. Marked bilateral diminution of vestibular response was noted during rotation tests and caloric tests.
Case 2 : an 80-year-old man had primary position downbeat nystagmus at a frequency of 1.5Hz and an amplitude of 2°-4°, which was not influenced by changes of eye position. Vertical optokinetic nystagmus tests were abnormal, but other neuro-otological findings were almost normal.
Case 3 : a 47-year-old woman showed primary position downbeat nystagmus with small amplitude (1°-2°) and 3 Hz frequency, which increased in intensity in the supine right-side-down position and changed to an upward vector in the head-hanging-position. VOR gain was greater than normal. There was almost total absence of visual suppression of caloric nystagmus.
The nystagmus observed in Case 1 seemed to reflect bilateral dysfunction of the caudal brainstem, including both vestibular nuclei, resulting from Wernicke's encephalopathy. The nystagmus in Case 3 originated from caudal brainstem compression by a large menigioma. In Case 2, no diagnosis was established.