Focal cortical dysplasia (FCD) is a type of malformation of cortical development that primarily affects areas of neocortex. It can be identified on conventional magnetic resonance imaging as focal cortical thickening, abnormal gyration, and blurring between gray and white matter, often associated with clusters of heterotopic neurons. Focal cortical dysplasia is one of the most common entities associated with refractory epilepsy, especially in childhood.
Taylor and colleagues1 wrote the first clear description of FCD in their report of pathological findings in lobectomy specimens from epilepsy surgery: "The most striking microscopic feature at low power was the localized disruption of the normal cortical lamination by an excess of large aberrant neurons scattered randomly through all but the first layer. . . . The aberrant nerve cells stood out partly because of their numbers and their inappropriate size, which at times approached that of a giant Betz cell, and partly because of their bizarre structure."1
Montenegro MA. Focal Cortical Dysplasia. Arch Neurol. 2003;60(4):634-636. doi:10.1001/archneur.60.4.634