Unusual associations of downbeat nystagmus

Abstract

Two patients presented with downbeat nystagmus and lesions remote from the cranio-cervical junction: one with decompensated aqueductal stenosis; the second with midbrain infarction. Unopposed upward drift of the eyes due to to vestibular or pursuit imbalance seem unlikely in the pathogenesis in these cases. An abnormality in the vertical gaze holding center is compatible with eye movement recordings in one case.

Key Words:

• downbeat nystagmus
• aqueduct stenosis
• midbrain infarction
• pathogenesis