Differential diagnosis of epileptogenic substrates of unknown etiology using a modification of the routine MRI protocol

Abstract

To evaluate the diagnostic capabilities of modifying the standard MRI protocol as part of an interdisciplinary presurgical examination of patients with epileptogenic substrates of unknown etiology. The results of dynamic MRI of 8 patients with a referral diagnosis of focal cortical dysplasia (FCD) were analyzed. In 7 patients, epilepsy was the reason for a standard MRI of the brain; in another patient with myasthenia, MRI was performed as part of a comprehensive examination. All patients, in addition to standard MRI, underwent a modification of the real-time scanning protocol to include contrast, tractography (DTI), and perfusion techniques (ASL/DSC). In 1 case, with questionable results, the results of a modification of the standard MRI protocol, high-resolution MRI (HR MRI) and hybrid positron emission CT with 11C-methionine (PET/CT with 11C-MET) were combined. Seven patients underwent epileptic surgery and 1 patient was operated on for a tumor. In 4 out of 8 patients, based on the results of a modification of the standard MRI protocol, radiological signs of a neoplastic process were identified, which suggested a low-grade tumor. One of them needed PET/CT to confirm the assumption. The results of pathomorphological examination correlated with the direct diagnosis for surgical treatment. One of the 4 patients was suspected to have dysembryoplastic neuroepithelial tumor (DNET) based on the results of the protocol modification, which was also confirmed by pathological examination. In another 4 patients in whom it was possible to narrow the differential between FCD type II and DNET based on the results of the modification, FCD IIb was pathomorphologically verified. The proposed modification of the standard MRI protocol can significantly facilitate the differential diagnosis between the neoplastic and dysplastic origin of an epileptogenic substrate of unknown etiology, which in turn affects the patient's management tactics.