A study on the correlation between electroencephalography characteristic and histopathological change in epilepsy patients due to focal cortical dysplasia

Abstract

Objective To study the histopathological characteristics and the correlations between the cortical tissues from ictal discharge (ID) area and interictal epileptiform discharge (IED) area in epilepsy patients due to focal cortical dysplasia (FCD), in order to further discuss the mechanism of epileptogenicity. Methods Twenty-two subjects who underwent epilepsy surgeries consecutively in our institute since April 2005 to August 2006. All patients underwent intracranial electrode implantations and long-term video-EEG monitoring before the resective surgeries and the postoperative pathologies proved to be FCD. According the long-term EEG monitoring results, the cortex with intense IED and the cortex with ID onset were resected separatively in the operation for further histopathologic studies. Twenty cases were collected. Based on the Palimini' s pathologic subtype classification for FCD as well as quantificational scoring for immunocytochemistry for the calcium-binding protein parvalbumin (PV) which we designed by ourself, the specimens of IED and ID were studied and compared. Results The resected specimens from 20 cases were examed. ID specimens showed more severe abnormalities in the laminar cortical architecture, alterations in the morphology of neurons and in the appearance of abnormal balloon cells. With the PV quantificational scoring, we found significant difference between IED (6.4±2.1) and ID (4.4±1.8) from FCD Ⅱ specimens (P=0.042). No difference was found between ID subtypes (F=2.734, P=0.093 ). Conclusions ID cortical area showed more severe abnormalities in histopathologic changes than lED area. Our results suggested that the ID area of FCD had more severe damage in inhibitory synaptic circuits and neural networks, which meant it was more epileptogenic than IED. No difference was identified between each ID subtype in term of epileptogenicity, which meant all of them should be resected during the surgery. Key words: Malformations of cortical development; Electroencephalography; Epilepsy