Purpose: Cortical specimens from six patients operated on for drug-resistant epilepsy diagnosed as Taylor's type focal cortical dysplasia were submitted to neuropathological and immunohistochemical studies.
Methods: All patients were submitted to presurgical investigations including clinical and neuropsychological evaluations, EEG/video telemetry of ictal and interictal events, magnetic resonance imaging, and ictal and interictal single-photon emission computed tomography (SPECT). Recordings from electrocorticography (ECoG) were obtained in four cases and from subdural electrode implantation in two. Postsurgical follow-up was assessed according to Engel's score. Immunohistochemistry (IHC) was processed for parvalbumin (PV), calbindin D28-K (CB), nonphosphorylated neurofilaments (SMI-311), glial fibrillary acidic protein (GFAP) in all cases.
Results: We found continuous/quasi-continuous spikes and sharp-wave patterns in three cases and frequent repetitive bursting of polyspikes and ECoG seizures in two cases. Every patient showed cortical dyslamination, abnormal and giant neurons, and balloon cells. GFAP immunoreactivity was found in astrocytes and some balloon cells that were less intensely stained. Nonphosphorylated neurofilaments SMI-311 immunoreactivity was found in normal and giant neurons and in some balloon cells, making visible thin neuropils. PV immunoreactivity was present in normal interneurons and in fibers in layers IV-V. PV-negative balloon cells were surrounded by abundant PV-positive fibers. CB immunoreactivity was found mostly in interneurons in layers II-III.
Conclusions: Our research is inconclusive. More cases should be investigated, and we must draw more accurate anatomic correlations between the ECoG recordings and surgical specimens studied with IHC.