Long-term Outcome of Epilepsy and Cortical Malformations Due to Abnormal Migration and Postmigrational Development: A Cohort Study

Objective: To evaluate the long-term outcomes of patients with epilepsy and malformations of cortical development (MCD).

Methods: We conducted a historical cohort study of patients with epilepsy and MCD due to impaired neuronal migration and postmigration organization with a follow-up period of ≥5 years. For each patient, MCD was classified after accurate neuroimaging reappraisal by an expert neuroradiologist. The primary outcome was remission, defined as a period of seizure freedom ≥5 years at any time from epilepsy onset. We used Kaplan-Meier estimates for survival analysis and univariate and multivariate Cox regression analyses to evaluate baseline variables as possible factors associated with remission.

Results: The cohort included 71 patients (M/F 31/40) with a 17-year median follow-up (1,506 person-years). About half (49.3%) had heterotopia, 35.2% polymicrogyria, 7% lissencephaly, and 8.5% the combination of 2 MCD. The mean age at seizure onset was 12.4 ± 7.2 years. Intellectual disability and neurologic deficits were observed in 30.4% and 40.9%, respectively. More than 60% of patients had refractory epilepsy. In 3 patients who underwent epilepsy surgery, MCD diagnosis was confirmed by histology. At the last visit, 44% of patients had been seizure-free during the previous year, but none of them had stopped antiseizure medication. Thirty patients achieved remission (42.2%) at some point in their disease history, whereas 41 individuals (57.8%) had never been in remission for ≥5 years. The cumulative remission rate was 38% by 20 years from inclusion. In the Cox model, unilateral distribution of MCD (hazard ratio [HR] 2.68, 95% CI 1.04-6.92) and a low seizure frequency at onset (HR 5.01, 95% CI 1.12-22.5) were significantly associated with remission.

Discussion: Patients with epilepsy and MCD showed a remission rate of 38% by 20 years from onset. Unilateral distribution of the MCD is associated with a 3-fold probability of achieving remission. About 40% of patients showed a drug-sensitive condition with risk of relapse during their epilepsy course.

Classification of evidence: This study provides Class II evidence that in patients with epilepsy and MCD, unilateral MCD and low seizure frequency at onset are associated with achieving epilepsy remission.