Congenital vertical pendular nystagmus in sisters.

Sisters with congenital vertical nystagmus are described in this report. In these 2 cases, the nystagmus on the electronystagmogram (ENG) showed a pure pendular pattern on forward gaze. Neurological examinations revealed no abnormality except for the nystagmus and visual disturbance. In the elder sister, the ENG showed that the intensity of the nystagmus decreased during eye closure and that there was no response to vertical optokinetic stimulation. We believe that the elder sister is the first case of congenital vertical pendular nystagmus confirmed by neuro-otological and neuro-ophthalmological examinations.