Long-term outcome of mild mesial temporal lobe epilepsy: A prospective longitudinal cohort study.

Objective: To identify clinical and imaging features at presentation that might predict long-term outcome in patients with mild mesial temporal lobe epilepsy (mMTLE), which is defined by at least 24 seizure-free months with or without antiepileptic medication.

Methods: In the setting of a prospective, population-based, longitudinal cohort study, we followed up 101 patients, all with mMTLE at enrolment. By protocol, patients underwent clinical evaluation every 3-12 months. Independent t test, Mann-Whitney test, or χ(2) test was used for comparing 2 groups. The incidence rate of refractory MTLE (rMTLE) was expressed as number of cases every 100 person-years.

Results: After a mean follow-up of 12.2 ± 3.7 years, 16 patients dropped out and 85/101 (mean age 46.5 ± 13.3 years) were available for the present analysis. Of these, 64/85 (75%) patients remained seizure-free and 21/85 (25%) became refractory (rMTLE), the latter corresponding to 2.0 cases per 100 persons per year. Patients with rMTLE showed a longer duration of epilepsy (p < 0.001), earlier age at epilepsy onset (p = 0.006), more frequent febrile convulsions (p = 0.02), and hippocampal sclerosis (HS) at MRI (p = 0.004) as compared to those with mMTLE.

Conclusions: mMTLE is a syndrome representing the mildest form of the wide spectrum of MTLE. Earlier age at onset, history of febrile convulsions, longer duration of epilepsy, and the presence of HS on MRI predict a worse outcome.