Herpesvirus infections: an important cause of pediatric hippocampal sclerosis

Objectives: As suggested from a high rate of preceding severe febrile convulsions, viral infections may be one cause of temporal lobe epilepsy (TLE). The impact of herpesvirus infections for TLE is uncertain.

Material and Methods: A detailed analysis of 23 pediatric patients (age 1–15 years) with epileptic seizures related to non-tumorous temporal lobe lesions, including hippocampal atrophy/dysplasia in 9 (group A) and hippocampal sclerosis in 14 cases (group B).

Results: Frequent febrile convulsions (n >3) preceding the diagnosis of TLE were noted in only three patients (13%) (group A=2, group B=1). No further etiological factors were detected in group A patients. Among group B patients, three had suffered serious perinatal events and two had shown an epileptic status during an encephalitic episode of unknown etiology. Surprisingly, in seven further group B patients distinct cerebral herpesvirus infections were found (HSV=3, EBV=2, CMV=2; intrathecal synthesis of specific anti-viral antibodies present). One additional girl developed severe hippocampal sclerosis when a primary EBV infection caused an epileptic status. Whereas additional inflammatory brain lesions were noted in patients with cerebral HSV infections, isolated hippocampal sclerosis was found in the five cases with CMV or EBV infections.

Conclusions: In addition to febrile convulsions that may cause neuronal damage by means of seizure-induced metabolic processes, distinct herpesvirus infections may be one further important cause of hippocampal sclerosis and TLE. The extent of brain damage may depend on the type of herpesvirus, ranging from isolated hippocampal sclerosis (CMV, EBV) to marked temporal lobe damage with additional brain lesions (HSV). Intensified research on the relationship between herpesvirus infections and temporal lobe damage may provide new treatment options for patients with TLE.