Epileptogenicity of Focal Malformations Due to Abnormal Cortical Development: Direct Electrocorticographic–Histopathologic Correlations

Abstract

Summary:Purpose: Malformations due to abnormal cortical development (MCDs) are common pathologic substrates of medically intractable epilepsy. The in situ epileptogenicity of these lesions as well as its relation to histopathologic changes remains unknown. The purpose of this study was to correlate the cellular patterns of MCDs with the expression of focal cortical epileptogenicity as assessed by direct extraoperative electrocorticographic (ECoG) recordings by using subdural grids.Methods: Fifteen patients with drug-resistant focal epilepsy due to pathologically confirmed MCD who underwent subdural electrode placement for extraoperative seizure localization and cortical mapping between 1997 and 2000 were included in the study. Areas of interictal spiking and ictal-onset patterns were identified and separated during surgery for further pathologic characterization (cellular and architectural). Three pathologic groups were identified: type I; architectural disorganization with/without giant neurons, type IIA; architectural disorganization with dysmorphic neurons, and type IIB; architectural disorganization, dysmorphic neurons, and balloon cells (BCs).The focal histopathologic subtypes of MCDs in cortical tissue resected were then retrospectively correlated with in situ extraoperative ECoG patterns.Results: Cortical areas with histopathologic subtype IIA showed significantly higher numbers of slow repetitive spike pattern in comparison with histopathologic type I (p ‫ס‬ 0.007) and normal pathology (p ‫ס‬ 0.002). The ictal onset came mainly from cortical areas with histopathologic type IIA (nine of 15 patients). None of the seizures originated from neocortical areas that showed BC-containing MCD (type IIB).Conclusions: This study shows that areas containing BCs are less epileptogenic than are closely located dysplastic regions. These results suggest a possible protective effect of BCs or a severe disruption in the neuronal networks in BCs containing dysplastic lesions. Further studies are needed to elucidate the nature and the potential role(s) of balloon cells in MCD-induced epileptogenicity.

Metabolic characteristics of cortical malformations causing epilepsy

“…Perilesional spectroscopic abnormalities have been previously reported [4,31], and two PET studies also showed perilesional changes [16,12]. Previous MRS studies found perilesional alterations to be less severe than those in the CM, a finding that would be consistent with partial voluming.…”

“…A 3D MRSI sequence, which covers the whole brain, might be a better technique to study these patients. 4. In addition to metabolite ratios we also calculated metabolite intensities but did not correct for variation of peak intensities due to coil inhomogeneities and susceptibility artifacts.…”

“…However, considering the fact that MRI visible CMs usually contain abnormal neuronal elements and are characterized by severe disturbances of the histological architecture, metabolic abnormalities are probably not restricted to NAA but affect also creatine/ phosphocreatine (Cr) and choline compounds (Cho). Furthermore, CMs can be histopathologically heterogeneous even within an individual lesion [4], and metabolic abnormalities can be expected to reflect this heterogeneity. Therefore, this study used MR spectroscopic imaging (MRSI) and tissue segmentation to test the following two hypotheses: 1.…”

Epilepsy Surgery in Patients With Tuberous Sclerosis

“…Вероятнее всего, это наблюдение объясняется тем, что транскор-тикальные очаги при ТС, несмотря на их визуализа-ционную схожесть, несколько отличаются от транс-кортикальных очагов при ФКД по клеточному составу: при ТС баллоновидные клетки превосходят количест-венно дисморфные нейроны, тогда как при ФКД типа IIb с транскортикальным признаком -наоборот [11]. Несколькими авторами было продемонстрировано, что эпилептические приступы в большей степени коррелируют с наличием дисморфных нейронов и менее -с наличием баллоновидных клеток [2,7,9,10]. Тем не менее представляется, что два других ти-па туберов (кальцинированные и кистоподобные) чаще сопряжены с генерацией эпилептических при-ступов [14].…”

The Principles of Surgical Treatment in Pediatric Epilepsy: Intractability to Medication, Determination of Potential Surgical Candidates and Advanced Techniques That Were Used for in Pediatric Epilepsy

“…Çalışmalar, epileptik aktivitenin tümörün içinden değil, onu çevreleyen yarı normal yarı anormal displastik dokudan kaynaklandığını göstermiştir. [13] Bu noktada, cerrahi olarak rezeksiyonun tüm epileptojenik zonu kapsaması için intraoperatif kayıtlamalar da değerlendirmeye eklenebilir.…”