Hippocampal sclerosis and encephalomalacia as prognostic factors of tuberculous meningitis-related and herpes simplex encephalitis-related epilepsy

BACKGROUND Tuberculous meningitis (TBM) and herpes simplex encephalitis (HSE) are common neurological diseases involving the brain parenchyma, and both can result in chronic epilepsy. Here, we identified possible variables affecting the prognosis of central nervous system (CNS) infection-related epilepsy. METHODS The clinical seizure characteristics and demographic data of 20 TBM- and 55 HSE-related epilepsy patients were compared. Statistically significant prognostic variables were identified using multiple regression analysis. RESULTS Sex, age at infection, age at epilepsy onset, presence of seizures at the time of infection, latency period, and seizure characteristics between two groups were similar except for the pattern of brain lesions observed on the MRI and their overall prognosis. Patients with hippocampal sclerosis (HS) only comprised 30% and 52.7% of the TBM and HSE groups, respectively. Encephalomalacia had a positive effect in the HSE group while HS had a negative effect in this group, but no significant effects were found in the TBM group. Through a multiple regression analysis with a correction for group effects, HS was associated with a poor prognosis. However, encephalomalacia was concomitantly associated with a good prognosis. In addition, a short latency period, with a one-year interval, and being male were both associated with a good prognosis, while the age at the onset of epilepsy was associated with a poor prognosis. CONCLUSIONS This study suggests that HS and encephalomalacia could have mutual but contradictory effects on the prognosis of CNS infection-related epilepsy.