Microscopic mild focal cortical dysplasia in temporal lobe dual pathology: An electrocorticography study

Abstract

Background: Associations between electrophysiological and histological findings might provide an insight into the epileptogenicity of mild focal cortical dysplasia (FCD) in patients with temporal lobe epilepsy (TLE) and a dual pathology. Subjects and methods: A total of 22 patients with pharmacoresistant TLE were included in the study, 16 of them with histologically confirmed hippocampal sclerosis (HS) associated with neocortical temporal mild Palmini Type-I FCD subtypes and 6 with HS. Intraoperative electrocorticography (ECoG) recordings were analysed for epileptiform discharge frequency and morphology. Associations between histological, and electrocorticography pattern findings in these patients were analysed. Electroclinical outcomes in these patients were also evaluated. Results: Neocortical areas with mild Palmini Type-I FCD showed a significantly higher spike frequency (SF) recorded in the inferior temporal gyrus than those neocortical areas in patients with HS. There was a tendency to higher spike frequency and lower amplitude in neocortical areas with histopathologic subtype IB FCD in relation with IA during intraoperative ECoG. Post-SF excision and amplitude were significantly lower during neocortical post-excision intraoperative ECoG than during neocortical preexcision recording. There was no difference found in the clinical outcome between patients with and without FCD. Conclusions: Intraoperative electrocorticographic interictal spike frequency recorded in the neocortical inferior temporal gyrus may help to characterize the histopathologic subtypes of mild Palmini Type-I FCD in patients with temporal lobe epilepsy (TLE) and a dual pathology. Our data support the epileptogenicity of neocortical mild FCD in TLE and assessments of ECoG patterns are relevant to determine the extent of the resection in these patients which can influence the electroclinical outcome.

How to record high‐frequency oscillations in epilepsy: A practical guideline

“…34,35 ECoG can be recorded with grid electrodes and subdural strips. It works well for dysplasias showing rhythmic spiking patterns.…”

“…It works well for dysplasias showing rhythmic spiking patterns. 34,35 ECoG can be recorded with grid electrodes and subdural strips. Subdural grids can be combined with depth electrodes directed at the lesion.…”

Surgery for focal cortical dysplasia in children using intraoperative mapping

“…Patients with FCD type IIb (Taylor-type) in the histology also have more frequently continuous or quasicontinuous rhythmic spiking or repetitive bursting pattern [8]. Fauser et al [19], using invasive EEG recording postulated that the histological subtype may influence the interictal electrographic patterns more than the localization of the lesion or the presence of dual pathology [42].…”

The role of voxel‐based morphometry in the detection of cortical dysplasia within the temporal pole in patients with intractable mesial temporal lobe epilepsy

“…FCD is a well-known frequent cause of medically refractory partial epilepsy in both children and adults (Kassubek et al, 2002;Tassi et al, 2002;Bautista et al, 2003;Colombo et al, 2003;Fauser & Schulze-Bonhage, 2006;Krsek et al, 2008;Colombo et al, 2009;Morales Chacón et al, 2009;Tassi et al, 2009). The epileptogenicity of FCD in TLE was confirmed with depth electrodes (Morales Chacón et al, 2009). This pathologic entity was first described in 1971 by Taylor et al (1971) as a disruption of cerebral cortical development.…”