Clinical phenotypes within non-surgical patients with mesial temporal lobe epilepsy caused by hippocampal sclerosis based on response to antiepileptic drugs

Abstract Purpose To evaluate evolution and elucidate clinical phenotypes related to prognosis of patients with mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS) treated exclusively with antiepileptic drugs (AED). Methods Forty-seven out of 68 MTLE-HS patients treated between January 2005 and June 2010 were retrospectively studied for demographic, clinical and outcome data. The population was divided into drug-responder and drug-resistant patients; the latter was divided, according to the duration of the seizure-free periods along their evolution, into patients with at least one seizure-free period longer than one year and those with shorter periods. Variables were compared between drug-responders vs drug-resistants and drug-resistants with long seizure-free periods vs drug-resistants without it. Results There were 7 (15%) drug-responders, 39 (83%) drug-resistants and 1 patient (2%) with an undetermined response. Eighteen (46%) drug-resistant individuals had seizure-free periods longer than one year, with mean duration of 46 months (3.8 years). Since no factor was statistically associated with long seizure-free period within drug-resistants, we can clinically distinguish two phenotypes: women with left HS and late onset of seizures, with poor prognosis, and men with right HS and earlier appearance of seizures, attaining a better outcome. Twenty out of 47 (42.5%) patients followed an intermittent pattern of epilepsy. Conclusions Non-surgical MTLE-HS drug-resistant patients can achieve long seizure-free periods with AED, but relapses are common. Female gender, left or bilateral lesion and later onset of seizures seem to be bad prognosis factors within MTLE-HS drug-resistant patients.