Landau-Kleffner syndrome: a pharmacologic study of five cases. Five children with Landau-Kleffner syndrome (epilepsy, acquired aphasia, and continuous spike-wave discharges during sleep), were treated with antiepileptic drugs (AEDs), sleep-modifying drugs, and corticosteroids. The pharmacologic profiles differed from those observed in focal epilepsies, resembling instead those of certain generalized epilepsies, such as West or Lennox-Gastaut syndromes. Phenobarbital (PB), carbamazepine (CBZ), and phenytoin (PHT) were ineffective or worsened the EEG and neuropsychological symptoms, whereas valproate (VPA), ethosuximide (ESM), and benzodiazepines were partially or transiently efficacious. Dextroamphetamine produced a dramatic but transient improvement in waking and sleep EEG in one of two children; aphasia did not change. Corticosteroid treatment resulted in improved speech, suppression of seizures, and normalization of the EEG in three of three children. Our own experience and data from the literature suggest that corticosteroids should be given in high doses as soon as the diagnosis is firmly established and should be continued in maintenance dose for several months or years to avoid escape. Early diagnosis, before mutism or global deterioration develops, appears to be essential for effective therapy with minimal neuropsychological sequelae. 