Anterior striatum with dysmorphic neurons associated with the epileptogenesis of focal cortical dysplasia

The epileptogenesis of the striatum is unknown. We describe the case of a 12-year-old girl with intractable epilepsy who was treated by surgical interventions. Magnetic resonance imaging (MRI) showed ambiguous corticomedullary boundary in the left frontal lobe, and magnetoencephalography (MEG) revealed spike dipoles in the vicinity of the left ventral striatum. The epileptic seizures disappeared after partial resection of the frontal lobe, but recurred within 2 months and remained intractable. Neuropathological examination confirmed the presence of focal cortical dysplasia in the resected brain tissue. Ictal single photon emission computed tomography at this period displayed hyperperfusion of the left anterior striatum. At the second surgery, intraoperative electrocorticography exhibited spike discharges from the anterior striatum. After the removal of this structure and adjacent brain tissues, the patient remains seizure-free for 33 months, without any neurological deficits. Histopathological examination of the resected tissue revealed a large number of dysmorphic neurons distributed widely in the cerebral cortex, subcortical white matter, striatum, and insular cortex. These findings suggest that microscopic dysplasia of basal ganglia can accompany certain cases of focal cortical malformations, and may play a critical role in the epileptogenesis through their interaction with cortical structures.