title: Downbeat nystagmus with phenytoin.
abstract: Downbeat nystagmus is generally the result of a structural lesion at the craniocervical junction. It has rarely been reported as a manifestation of metabolic disease or drug intoxication. We observed two patients with downbeat nystagmus secondary to phenytoin (Dilantin) intoxication. Both individuals had other features of phenytoin-induced central nervous system dysfunction with toxic blood levels of the drug (greater than 20 micrograms/ml). Complete resolution of the downbeat nystagmus followed the return of phenytoin levels to the therapeutic range.
mesh_terms: D000328:Adult; D001259:Ataxia / Q000139:chemically induced; D002493:Central Nervous System Diseases / Q000139:chemically induced*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009759:Nystagmus, Pathologic / Q000139:chemically induced*; D010672:Phenytoin / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D012640:Seizures / Q000188:drug therapy
chemical_list: D010672:Phenytoin