Continuous EEG-fMRI study in patients with partial epilepsy and focal interictal slow-wave discharges on EEG

Purpose: To study, with continuous EEG-fMRI, eight patients affected by partial seizures using and presenting with focal interictal slow-waves activity on routine scalp EEG recordings. Methods: Twenty-four minutes (4 sessions) of continuous EEG were recorded from 18 scalp electrodes while fMRI images were simultaneously acquired using a 1.5 Tesla MRI scanner. After recording sessions and MRI artefact removing, EEG data were analyzed offline. We detected BOLD activation on fMRI deriving from comparision of two conditions: resting (that is EEG sequences without focal interictal slow-wave activity) vs activation states (EEG with focal interictal slow-wave activity). Results: In all patients, focal interictal slow-waves activity was invariably associated with a significant increase in the focal BOLD signal. We detected a significant concordance between focal interictal slow-waves activity on EEG and focal BOLD activation on fMRI. In lesional epilepsy there was a concordance between the epileptogenic area and the focal BOLD signal. Conclusions: EEG-fMRI may be useful even in determining focal BOLD activation linked to interictal slow-waves activity in patients affected by partial seizures, so even this EEG marker (and not only spikes) may be useful to trigger fMRI.