Abstracts

Rationale: Patients with periventricular nodular heterotopia (PVNH) have epilepsy, and there is likely to have a complex interaction between epileptogenic nodular tissue and overlying cortex. However, it is unclear whether the epileptic focus is the nodule, overlying cortex, or both. Combined scalp EEG and functional MRI (EEG-fMRI) may provide an interesting non-invasive alternative tool to understand those mechanisms in PVNH. The aim of this study was to reveal the cerebral structures active during interictal epileptiform discharges (IEDs) in PVNH using EEG-fMRI. Methods: We investigated 8 epileptic patients with PVNH (6 females, mean age, 29.3 ± 5.2 years; bilateral PVNH in 7 and unilateral in 1) using simultaneous recording of EEG-fMRI inside a 3 T MRI scan. EEG was continuously acquired from inside the scanner. IEDs were visually identified in the filtered EEG. Imaging data were analyzed using SPM8 with canonical hemodynamic response function to detect fMRI BOLD activation and correlated BOLD changes with location of PVNH in each patient. Results: Among 8 patients, two patients were not analyzed because of the absence or rare number of IEDs during recording. In remaining 6 patients, 5 of 6 patients showed BOLD activation. In five patients with BOLD activations, 3 patients only showed BOLD activations around PVNH, 1 showed only overlying cortex without PVNH and 1 showed both PVNH and overlying cortex area. Conclusions: This study revealed that heterotopia and/or overlying cortical areas were simultaneously or predominantly involved in BOLD changes during IED depending on the patients.