Late-onset epilepsy associated with regional brain cortical dysplasia

Cortical dysplasia (CD) designates a diverse group of malformations resulting from one or more abnormalities in the development of the cerebral cortex. The clinical manifestations of CD are varied, probably depending on the type, location and extent of CD. Epilepsy is a potential late manifestation of any cortical malformation. To our knowledge, however, no study has focused specifically on late onset of epilepsy in patients with localized CD.

We studied patients with localized CD confirmed by MRI. Patients were divided into 2 groups according to age at onset of epilepsy. Group 1 included patients in whom the first seizure occurred up to the age of 12 (early-onset group) and group 2 included patients in whom the first seizure occurred after the age of 12 (late-onset group). The two groups were compared with regard to the type of CD, clinical findings and EEG findings.

Thirty-three patients with various forms of CD were studied. Onset of epilepsy occurred in adolescence or adulthood in 9 cases (37%). In 6 of these (17% overall), the first seizure occurred in adulthood. CD were posterior bilateral pachygyria (1), unilateral polymicrogyria (3), focal dysplasia with subcortical gray matter heterotopia (1), perisylvian bilateral polymicrogyria (1), bioccipital polymicrogyria (1) and bilateral nodular periventricular gray matter heterotopia (2). The incidence of neurological signs was lower in the late-onset group. Mental retardation was moderate or absent, thus allowing a fairly normal lifestyle. All patients presented partial seizures with a lower incidence of drug resistance (p < 0.01). EEG demonstrated preservation of background activity and absence of diffuse or multifocal abnormalities.

Onset of epilepsy with various forms of CD may be delayed until adolescence or adulthood. Prognosis of epilepsy is usually more favorable in these cases.