Identification of the Epileptogenic Tuber in Patients with Tuberous Sclerosis: A Comparison of High‐resolution EEG and MEG

Abstract

Summary:Purpose: We compared epileptiform activity recorded with EEG and magnetoencephalography (MEG) in 19 patients with tuberous sclerosis complex (TSC) and epilepsy.Methods: High-resolution (HR) EEG, HR-MEG, and 1.5-T MRI scans were performed. Epileptiform spikes were identified in EEG and MEG recordings offline by three observers. Spikes for which the interobserver agreement (spike consensus) was >0.40 were used for source localization with CURRYV 3.0 software. MUSIC analysis was performed. The distance between the source determined from EEG and MEG recordings and the border of the closest tuber was calculated and compared.Results: Consensus spikes (kappa >0.4) were identified in 12 patients in the EEG recording and in 14 patients in the MEG recording. MEG sources were closer to tubers in all but one patient. Three patients underwent epilepsy surgery, two of whom are seizure free after complete resection of the tuber.Conclusions: In patients with TSC, epileptogenic sources identified on MEG are closer to the presumed epileptogenic tuber than are similar sources identified on EEG. Moreover, spike consensus is greater with MEG. Clear identification of the epileptogenic zone may offer opportunities for surgery in patients with TSC with intractable epilepsy. Key Words: Tuberous sclerosis-Epilepsy-MEG-EEG.Tuberous sclerosis complex (TSC) is a neurocutaneous syndrome, involving multiple organs. The characteristic hamartomas are most commonly found in the skin, retina, heart, kidney, and brain. TSC is an autosomal dominant disorder with linkage to chromosome 9q34 (TSC1) (1) and chromosome 16p13 (TSC2) (2). Hamartin and tuberin, the protein products of TSC1 and TSC2, respectively, are tumor-suppressor genes.In the CNS, the disordered proliferation, migration, and differentiation of neurons as a result of TSC give rise to noduli, subependymal giant-cell astrocytomas, and cortical tubers (3). Cortical tubers are associated with neurologic symptoms, such as epilepsy, mental retardation, and focal neurologic deficit. Although the phenotypic expression of TSC is extremely variable, seizures are common, occurring in 80-90% of cases, and are often the presenting symptom. Furthermore, they are often intractable (50%). Surgery should be considered in patients with TSC and drug-resistant epilepsy, but it may be difficult to identify the epileptogenic tuber if several tubers are distributed Accepted July 22, 2005. Address correspondence and reprint requests to Dr. F.E. Jansen at Department of Neurology, C03236, University Medical Center, PO Box 85500, 3508 GA Utrecht, The Netherlands. E-mail: f.e.jansen@neuro.azu.nl throughout the cerebral cortex. To date, the outcome of surgery has been variable in children with TSC (4-10).Although structural and functional imaging techniques [MRI, functional MRI (f MRI), single-photon emission computed tomography (SPECT), positron emission tomography (PET)] are being increasingly used in patient workup, epileptiform activity can be recorded only with neurophysiologic techniques. With standar...

Epilepsy surgery in tuberous sclerosis: a review

“…Additionally, the epileptogenic foci were closer to the presumed epileptogenic tubers with MEG when these results were superimposed on MRIs. 16 In a study of noninvasive testing using magnetic source imaging and FDG-PET, resection that included the magnetic source imaging dipole clusters was associated with seizure-free outcomes. In 75% of patients, MEG confirmed the localization from scalp EEG.…”

Epilepsy surgery and tuberous sclerosis complex: special considerations

“…25,72 Based on the experience of several investigators over the last 20 years, the efficacy of surgery is well established for controlling seizures in patients with TSC with concordant and localized neuroimaging and electrophysiological Epilepsy surgery for medically refractory seizures among patients with tuberous sclerosis complex (TSC) is a wellaccepted treatment option. Many epilepsy centers around the world have published their experience over the past several years, supporting the idea that the best seizure control is obtained when a single tuber and associated epileptogenic zone is documented and targeted surgically.…”

Epilepsy Surgery in Patients With Tuberous Sclerosis

“…Об-щепринятый протокол по времени и способу приме-нения вспомогательных тестов (в дополнение к дли-тельному видео-ЭЭГ-мониторингу и МРТ) в определении эпилептогенной области при ТС отсут-ствует. В течение многих лет один педиатрический центр (Детройт) ввиду относительно низкой инфор-мативности ПЭТ с фтордезоксиглюкозой -ПЭТ при определении этиологии заболеваний, характери-зуемых множественными очагами [55], в значительной степени опирался на AMT / ПЭТ [3,12,39,41], другие эксперты верят в ценность ОФЭКТ [1,43] или магни-тоэнцефалографии [31]. Есть причина полагать, что комбинация этих исследований может обладать более высокой положительной прогностической цен-ностью, чем отдельные тесты, при определении исхо-да эпилептических приступов после операции, как в случае, когда магнитография комбинируется с ПЭТ / МРТ [68].…”