Multi-focal occurrence of cortical dysplasia in epilepsy patients

This study describes the existence and the clinical and electrophysiological features of multi-focal cortical dysplasia in epilepsy patients. Five patients with intractable focal epilepsy are reported. All patients underwent invasive presurgical video-electroencephalography monitoring. Localization of dysplastic areas was based on high-resolution magnetic resonance scanning, surface and intracranial electroencephalography. Four patients underwent epilepsy surgery. Histological findings in focal cortical dysplasia (FCD) were classified according to Palmini. In addition, genetic examinations were performed in order to assess possible mutations in the genes for tuberous sclerosis complex. In four patients, FCDs were located in the same hemisphere. One case presented with bilateral FCDs. In three patients seizures arose from two separate dysplastic areas and in one patient, one lesion showed only interictal activity. In one further patient, seizures started exclusively from the hippocampus. In two of three patients with removal of the FCDs, the histological subtype was identical (Palmini type 2) and in one patient, histology differed between the lesions. All operated patients became seizure-free. In patients with FCD type 2, germ-line mutations in the tuberous sclerosis complex genes were not detectable. Dysplastic brain regions may not be restricted to a single brain region. Areas of FCD can have different degrees of epileptogenicity, ranging from electrographic silence to interictal epileptic discharges and initial involvement in seizure generation. Based on genetic analysis and clinical features, multi-FCD in this patient series was not likely to be related to tuberous sclerosis.