Upbeat and downbeat nystagmus occurring successively in a patient with posterior medullary haemorrhage.

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Abstract
In a patient with posterior medullary haemorrhage, first upbeat and later downbeat nystagmus occurred in the primary position. The lesion was limited to the posterior and medial part of the medulla. Clinical and electro-oculographic examination first showed upbeat nystagmus in the primary position and upgaze, with downbeat nystagmus in downgaze. Two and a half months later, there was downbeat nystagmus in the primary position and downgaze and upbeat nystagmus in upgaze.