Seizure outcome after surgery for epilepsy due to malformation of corticaldevelopment

Purpose: To explore seizure outcome after surgery for focal epilepsy due to malformation of cortical development (MCD), with focus on the role of MRI. Methods: Thirty-five patients who had surgery for intractable focal epilep sy due to MCD identified by preoperative MRI and confirmed by histopatholog ic analysis of resected tissue were studied. Patients were aged 3 months to 47 years (median, 14 years) at the time of surgery. Duration of follow-up was 1 to 7.9 (mean, 3.4) years. Results: At latest follow-up, 17 patients ( 49%) had Engel Class I outcome with no seizures or auras only; eight patien ts (23%) had Class II outcome, with rare disabling seizures; seven patients (20%) had worthwhile improvement; and three patients (9%) had no improveme nt. Seizure-free outcome tended to be more frequent among patients who had complete resection of unilateral MCD (excluding hemimegaleneephaly) based o n postoperative MRI (7/12; 58%), compared with patients with unilateral MCD who had incomplete resection (3/11; 27%), but the difference was not signi ficant. The frequeney of seizure-free outcome did not differ significantly between children (8/14; 57%), adolescents (7/15; 41%) or adults (2/6; 33%); between patients who had daily (12/24; 50%), weekly (4/9; 44%), or monthly (1/2; 50%) seizures preoperatively; between patients who had temporal (2/6 ; 33%) or extratemporal or multilobar resections (14/28; 50%); or between p atients who were (9/16; 56%) or were not (8/19; 42%) studied with subdural electrodes. Results for all analyses were similar when analyzed at latest a vailable follow-up or at 1 year after surgery. Conclusions: Surgery can off er seizure-free outcome for approximately one half of carefully selected pa tients with intractable focal epilepsy due to MCD. Complete resection of th e MRI-apparent lesion may improve the likelihood for favorable outcome. MRI evidence of hemimegalencephaly or bilateral MCD suggests a low Likelihood for postoperative freedom from seizures.