Epilepsy and Cortical Dysplasias.

Focal cortical dysplasias (FCD) and diffuse cortical dysplasias (DCD) are a heterogeneous group of disorders defined by abnormal cerebral cortical cytoarchitecture that are associated with epilepsy. Patients with either DCD or FCD may suffer from a variety of epilepsy subtypes and these are often refractory to most anti-epileptic drugs (AEDs) despite polytherapy. The etiologies of cortical dysplasias (CD) are diverse, and include inherited genetic syndromes such as Miller-Dieker or X-linked lissencephaly, subcortical band heterotopia, and the tuberous sclerosis complex, as well as nongenetic exogenous insults such as hypoxic-ischemic injury, viral or other type of central nervous system infection, or traumatic injury. A large number of FCD cases are idiopathic and very small regions of FCD (microdysgenesis) are now being identified in resected epilepsy specimens. Recent data suggests that nearly 30% of epilepsy specimens evaluated histologically will contain regions of overt or microscopic CD. The mainstay of appropriate therapy for CD remains the standard AEDs or epilepsy surgery. In too few disorders, specific AEDs provide therapeutic advantage in the setting of individual forms of CD. The ketogenic diet may provide seizure control in a subpopulation of patients. In both DCD and FCD, surgical resection can be curative in the appropriately selected patients. Surgical approaches include focal neocortical resections, temporal lobectomy, or larger hemispheric resection procedures.