Neuropathological findings in patients with mesiotemporal epilepsy: Frequent occurrence of dual pathology
Abstract
Background: The most frequent type of pharmacoresistant epilepsy indicated for surgical therapy is mesiotemporal epilepsy (MTLE). Typical structural basis of MTLE is mesiotemporal sclerosis (MTS); however, it becomes evident that diverse histopathology and etiopathogenesis make patients with MTS a heterogeneous group.
In some of them, dual pathology, i.e., focal lesion of temporal neocortex is found in combination with MTS. Methods: We have histologically analysed resected brain tissue of 15 patients (age 17-38 years) with the diagnosis of MTLE who were indicated for anteromesial temporal resection; their neuropathological findings were correlated with data from clinical history and the results of preoperative examinations.
Standard preoperative investigation protocol included electrophysiology (EEG, video EEG), imaging (MRI), functional (SPECT, PET, MRS) and neuropsychological exams. Both mesial archicortical structures and temporal pole neocortex were analysed with conventional histological techniques.
Results: In all cases, histology confirmed the clinical suspicion of MTS; in addition, dual pathology was detected in 9 out of 15 patients. These were predominantly congenital malformations of cortical development (in 7 cases).
Only in one case was the dual pathology uncovered with preoperative examinations. The initial insult that is probably connected to the development of MTS (complicated febrile seizures, craniocerebral trauma, meningoencephalitis) has been found in clinical history in 12 patients (80%).
In all three patients without predisposing clinical history, there was an congenital abnormality of neocortex. Discussion: We believe that in some patients lacking the initial insult, MTS arises specifically as a result of congenital cortical changes.
From the presented data it is evident that neuropathological examination not only significantly contributes to understanding of the etiopathogenesis of pharmacoresistant epilepsy but also it can influence the therapeutical approach in epileptosurgical patients.