Clinical detection of acute vestibulocerebellar disorders.

The acute onset of vertigo, nystagmus and postural instability, without brain-stem signs, is commonly attributed to a disorder of the labyrinth, the vestibular, sensory end organ. Identical symptoms can occur, however, with discrete infarctions or hemorrhages involving the central vestibulocerebellum. Whereas acute labyrinthine disorders are usually benign and self-limited, vascular injuries of the cerebellum may produce swelling, compression of the brain stem and acute hydrocephalus one to four days after the onset of symptoms. Therefore it is important to accurately distinguish between labyrinthine and vestibulocerebellar disorders with the neurologic examination. Acute labyrinthine disease causes unidirectional nystagmus with past-pointing and falling in the opposite direction of the nystagmus, environmental vertigo in the same direction and suppression of the nystagmus with visual fixation. Disorders of the vestibulocerebellum do not produce this consistent pattern of findings.