Further observations on the syndrome of chronic encephalitis and epilepsy.

This report is a sequel to our 1958, 1960 and 1968 reports on a series of patients operated upon for focal epilepsy whose surgical specimens unexpectedly showed histological lesions typical of active encephalitis. None of these patients, now 27 in number, exhibited the clinical picture ordinarily associated with encephalitis. With one exception, all showed a severe focal seizure tendency beginning in infancy or childhood, often associated with episodes of epilepsia partialis continua. In addition, all except 2 showed slowly progressive neurological deterioration, usually hemiparesis and mental retardation, which advanced over periods of months or years before the progression became arrested. No infectious agent has yet been identified by standard viral studies carried out in the most recent 14 patients or by investigation for slow viruses in 6 patients operated upon between 1966 and 1971. The clinical course of this condition is outlined and the role, the timing and the results of treatment by craniotomy and cortical excision are discussed.