Two cases of downbeat nystagmus and oscillopsia associated with carbamazepine.

Downbeat nystagmus is often associated with structural lesions at the craniocervical junction, but has occasionally been reported as a manifestation of metabolic imbalance or drug intoxication. We recorded the eye movements of two patients with reversible downbeat nystagmus related to carbamazepine therapy. The nystagmus of both patients resolved after reduction of the serum carbamazepine levels. Neuroradiologic investigations including magnetic resonance imaging scans in both patients showed no evidence of intracranial abnormality. In patients with downbeat nystagmus who are taking anticonvulsant medications, consideration should be given to reduction in dose before further investigation is undertaken.