The EEG was studied in five children with Landau-Kleffner syndrome at the Service de Neurologie I, Hopital Central, Strasbourg, France, and Department de Neurologie C.H.U. Sart Tilmman, Liege, Belgium. Day and nighttime EEG video monitoring was performed before and after each change of therapy. One hundred EEGs of 30 minute to two hour duration were recorded on awake patients. Sleep EEGs were obtained during five spontaneous daytime naps, 15 naps induced by amitriptyline, and 65 complete nights of sleep. Spike-wave duration was measured as a percentage of the total sleep period. The EEG in waking patients showed focal and generalized spike-wave discharges on a normal background rhythm. During sleep, discharges increased and bilateral spike-waves occurred more than 85% of the sleep period. The abnormal EEG and the impairment of higher cognitive function developed and regressed together. It was difficult to differentiate the Landau-Kleffner syndrome and “Epilepsy with continuous spike-waves during slow wave sleep”. Only the neuropsychological features differed. They are probably variations of a single syndrome. 
COMMENT. In the classical Landau-Kleffner syndrome aphasia is acquired and other higher cortical functions do not usually deteriorate. In the “continuous spike-wave activity during sleep syndrome” speech is disturbed in 50% of cases but intellectual deterioration occurs and psychiatric disorders develop. In three of the five patients studied by the authors, only treatment by corticosteroids had lasting effects in correcting the regression of higher functions and EEG abnormalities. Phenobarbital, carbamazepine, and phenytoin were either ineffective or exacerbated the EEG and neuropsychological abnormalities . These authors recommend that high doses of corticosteroids should be administered early at the first appearance of symptoms and preferably before total aphasia or intellectual regression occur and treatment should be maintained at lower doses for a period of months. An abnormal pattern of cerebral glucose utilization demonstrated in three children with Landau-Kleffner syndrome by PET study is reported by the same group of authors from Liege, Belgium and Strasbourg, France . The specificity of the metabolic abnormalities and their relationship to the aphasia and EEG remain to be determined.