Toxicology observation: nystagmus after marijuana use.

Traditional teaching has held that horizontal-gaze nystagmus is a sign of intoxication by sedatives such as alcohol but not marijuana. This is a case report of an adult male who presents with 3 days of visual disturbance and dizziness following marijuana use. The exam was notable for gaze-evoked nystagmus and ataxia. Lab testing was normal except that urine drug screening was positive for marijuana only. Imaging included computed tomography (CT) and magnetic resonance imaging (MRI) scans of the head. Prior studies showing a negative association of nystagmus with marijuana are reviewed. This case is presented as a possible exception to the generalisation that marijuana is not associated with nystagmus.