The presence of herpes simplex virus (HSV) was determined by polymerase chain reaction in surgical specimens from 50 patients (13 to 58 years of age) with epilepsy obtained from multiple centers, including the National Neurological Research Specimen Bank, West Los Angeles Veterans Affairs Medical Center, Los Angeles, CA. Twenty (40%) of the 50 epilepsy surgical cases and only 2 (4%) of 48 control autopsy specimens from Alzheimer and Parkinson disease patients tested positive for HSV. Heterotopias were the most frequent epileptic tissue abnormalities (12 cases), and 67% tested positive for HIV. Of 8 with hippocampal sclerosis, 50% were HIV positive. 
COMMENT. Although this finding of herpes simplex virus in epileptogenic cerebral tissue does not prove a causative effect, the association is provocative and should stimulate research of possible viral etiology of refractory epilepsies in children, especially those with evidence of heterotopias, infantile spasms, complex febrile seizures, and perhaps, the Landau-Kleffner syndrome. A trial of acyclovir may be considered in some.