A distinct variant of focal cortical dysplasia type I characterised by magnetic resonance imaging and neuropathological examination in children with severe epilepsies.

Focal Cortical Dysplasias (FCDs) present with a large clinicopathological spectrum. FCDs are believed to relate directly to an epileptogenic condition, although seizure control by surgical resection is variable. This applies in particular to young children with multilobar FCDs, suffering from severe epilepsies and psychomotor retardation. Herein, we performed a comparative analysis of presurgically available data and microscopic inspection of resected cortical specimens to further characterise the pathomorphological spectrum of FCD. Multilobar resection procedures were performed in a consecutive series of 18 young children (mean 7.6 years) with severe pharmaco-resistant epilepsies following extensive presurgical surface-/invasive video-EEG monitoring intraoperative electro-corticography (iECoG), as well as high resolution MRI. In all cases, systematic neuropathological examination of surgical specimens was performed with respect to architectural abnormalities and cell density measurements. These histomorphological data were compared with volumetric MRI analysis. Histopathological examination revealed increased neuronal densities correlating with decreased cortical thickness and abundance of neuronal microcolumns in all cases. Intriguingly, the affected cerebral hemisphere was significantly smaller, relative to the non-epileptogenic contralateral side, in 16 children of our patient series. In conclusion, hypoplastic neocortex and columnar architectural disorganisation point to compromised cortical development, and appear as distinct FCD I subtype in children suffering from severe epilepsies and psychomotor retardation.

Different presurgical characteristics and seizure outcomes in children with focal cortical dysplasia type I or II.

PURPOSE: Cortical dysplasia (FCD) is a frequent cause of epilepsy in childhood. Two major pathological variants are distinguished, FCD type I and II. The aim of the study was to characterize differences between FCD type I and II with respect to imaging and EEG findings, clinical and neuropsychological presentations, and surgical outcome. METHODS: Forty children with refractory epilepsy and histopathologically confirmed FCD were retrospectively analyzed. FCD type I was identified in 24 and FCD type II in 16 patients. RESULTS: Characteristic MRI abnormalities in FCD type I included subtle white matter signal changes and regional reduction of the white matter volume. Typical MRI findings in FCD type II were increased cortical thickness, transmantle sign, gray-white matter junction blurring, fluid-attenuated inversion recovery (FLAIR) and proton density (PD) gray matter signal changes as well as T1w, and PD white matter signal changes. Continuous EEG slowing was significantly more common in patients with FCD type I. Children with FCD type I presented with lower levels of intelligence and were suffering more often from maladaptive behavior and behavioral disorders. Surgical outcome was significantly worse in the FCD type I group (seizure freedom was achieved in 21% FCD type I patients and in 75% FCD type II subjects, p < 0.001). CONCLUSIONS: Clinically important differences were found in children with distinct histopathological subtypes of FCD. Due to prominent neuropsychological deficits and worse seizure outcome, treatment strategies in FCD type I are more challenging than previously reported and these children should be recognized and specifically addressed within the incoherent group of patients with malformative brain disorders.