Focal cortical dysplasia-associated tumors: resecting beyond the lesion.

Commentary Low-grade supratentorial tumors constitute 10 to 40% of the pathological diagnoses in patients following resective surgery for refractory focal-onset epilepsy (1, 2). The most common tumor subtypes in this group include inherently indolent and intrinsically epileptogenic gangliogliomas (GG) (3) and dys-embryoplastic neuroepithelial tumors (DNT). Temporal lobe tumors in this group exhibit certain distinct features. About 90% of such tumors were found within or adjacent to the gray–white junction or hippocampal formation with frequent involvement of associated mesial temporal structures (4, 5). Several studies have identified young age, male predominance , long history of refractory epilepsy, healthy neurological examination, an indolent biological nature with long-term survival, and favorable surgical outcome as common characteristics in this group (6, 4, 5). Supratentorial GG and DNT tumors demonstrate a strong association with focal cortical dysplasias (FCD). It is notable that FCD are a common cause of intractable epilepsy in both children and adults. It is well-known that FCD are associated with epileptogenic brain tissue, although surgical resection achieves seizure control to a variable extent (7, 8). The optimal surgical strategy for these patients continues to be debated. Some centers typically recommend, when possible, isolated tumor resec-tion while others include resection of surrounding epileptogen-ic structures guided by electrocorticography (ECoG). Such ECoG studies have challenged the idea that epilepsy in a subgroup of FCD is associated with a solitary epileptogenic lesion. That is, epileptogenic areas remote from the primary dysplastic lesion are often associated with less favorable clinical outcomes. All forms of FCD lead to disorganization of the normal structure of the cerebral cortex. Characteristic findings include often subtle aberrant radial or tangential lamination of the neocortex (FCD Type I) and/or cytological abnormalities (FCD Type II). FCD in combination with GG and DNT tumors appear to occur isolated in temporal and/or extratemporal regions. In particular, FCD Type I is associated with subtle neuroimaging, histopathology, and less favorable post resective seizure outcomes. The indolent progression and associated epileptogenicity of glioneural tumors have raised the hypothesis of a developmental rather than neoplastic origin of these lesions (9). A recent International League Against Epilepsy (ILAE) task force has re-evaluated available data and proposed a neu-ropathological classification system of FCD (10). The major modification to the previous classification includes the intro-The goal of the present study was to evaluate the clinical characteristics and postoperative seizure outcome of epi-leptogenic tumors associated with focal cortical dysplasias (FCDs) compared to both solitary …