The role of cerebral cyst formation in the intractability of epilepsy

Abstract

Objectives: The aims of the present study were: (1) to examine single focal, intractable epilepsy associated with gliotic changes and (2) to discuss the mechanisms underlying seizure intractability.Patients and methods: Records of 34 patients with surgically treated intractable epilepsy were analysed retrospectively. Thirteen out of 34 patients had single epileptic focus histologically identified as a gliotic change. Seizure types, neuroradiological findings including the location and size of the foci, the hemosiderin deposition and calcification, intra-operative findings, and pathological findings of 13 patients were analysed in this study. Whether cyst formation was presented was also recorded. Tailored resections of epileptogenic lesions were performed using electrocorticography and ultrasonography.Results: Cyst formations were observed in 10 out of 13 patients. In eight of the patients with cyst formation, seizures initially were well controlled, but the subsequent seizures increased in both severity and frequency in a stepwise manner. All patients with cyst formation became seizure free after the removal of the cyst wall and surrounding gliotic tissue.Conclusions: Analyses of the clinical courses, pathological and hydrodynamic findings suggest that the gliotic changes secondarily induced by cystic changes in brain parenchyma appear to play an important role in seizure intractability. We adapted the 'Starling resistor model' of hydrodynamics as a hypothetical model for the intracranial cyst and fluid passage to explain the mechanisms of the formation of epileptogenic gliotic changes.