Mild non-lesional temporal lobe epilepsy. A common, unrecognized disorder with onset in adulthood.

OBJECTIVE To compare mild vs. severe non-lesional temporal lobe epilepsy (TLE). METHODS Data from 104 consecutive patients with non-lesional TLE were reviewed. Seventy-three of the 104 fulfilled the criteria for inclusion in this study of a follow-up period longer than three years at our Institute. Patients were considered to have a mild TLE if they were seizure free for at least three years after appropriate antiepileptic medication, or had rare (< or = 2/year) complex partial or secondarily generalized seizures for at least three years with or without appropriate antiepileptic therapy. Clinical, EEG and MRI data of mild vs. severe non-lesional TLE patients were compared on the basis of a cross-sectional study design. RESULTS Of the 73 patients with non-lesional TLE included in the study, 43 (59%) had mild TLE, and 30 (41%) had severe TLE. Duration of epilepsy was significantly shorter (mean 15.2 +/- 10.5 years vs. 26.4 +/- 13.2 years) and age at onset was significantly higher (mean 34.3 +/- 15.3 years vs. 7.8 +/- 6.8 years) in mild than in severe TLE group. Patients with mild TLE had also a significantly higher prevalence of positive family history of epilepsy (37.2% vs. 10%), and a significantly lower occurrence rate of febrile convulsions (FC) (4.7% vs. 33.3%), mesial temporal sclerosis (MTS) (6.9% vs. 36.7%), and intelligence deficiency (0% vs. 20%). In mild TLE there was also a significantly high rate (58.1 vs. 0%) of delayed diagnosis (from 1 to 28 years), because of misdiagnosis (39.5%) or no medical counseling (18.6%). CONCLUSIONS Mild non-lesional TLE is a common, unrecognized disorder mainly characterized by both onset in adulthood and high prevalence of familial history of epilepsy. The present findings suggest that mild non-lesional TLE may represent a clinical entity different from severe non-lesional TLE.