Clinical characteristics and post-surgical outcomes of focal cortical dysplasia subtypes

We retrospectively studied 105 patients with a focal cortical dysplasia (FCD) diagnosed on pathological examination, and investigated the long term postoperative seizure outcomes, different clinical characteristics of the three FCD subtypes, particularly type I and II, and surgical outcomes for each group. FCD is a common cause of drug-resistant epilepsy, which is divided into three different subtypes according to its involvement at different stages of brain development. Each of these groups may have different characteristics and may even have different surgical outcomes. After treatment, 55% of patients were completely seizure-free, with two significant predictive variables for poorer outcomes: focal MRI findings and electrode implantation. FCD type I had relatively poor surgical outcomes compared to FCD type II and type IIIa. Compared with FCD type I, type II, particularly IIb, had a higher frequency of seizure attacks, predominantly located in the extratemporal lobes, and was more readily detected and diagnosed via focal lesions on MRI and localized electroencephalogram abnormalities. FCD type II patients seem to show better surgical outcomes than FCD type I, but the difference was not significant. Larger cohort studies are needed for further evaluation of the seizure outcomes of different FCD subtypes.