EEG-fMRI in modalità continua su pazienti affetti da epilessia parziale e focolaio irritativo a onde lente all'EGG

Introduction. Epilepsy of surgical interest needs to be studied with techniques distinguishing epileptogenic vs irritative areas, because only the first has a surgical interest. One of these new techniques is EEGfMRI, so now applied to patients with a spiked irritative focus. Only few studies (Laufs 2006, Avesani 2008, Manganotti 2008) considered a slow wave irritative focus. Purpose: To verify whether in patients with partial epilepsy and routine electroencephalogram (EEG) showing focal interictal slow-wave discharges without spikes combined EEG-functional magnetic resonance imaging (fMRI) would localize the corresponding epileptogenic focus, thus providing reliable information on the epileptic source. Methods: 16 patients with partial epileptic seizures whose routine scalp EEG recordings on presentation showed frequent focal interictal slow-wave activity (almost 2 IEDs/min) underwent EEG-fMRI. EEG data were continuously recorded for 24 min (four concatenated sessions) from 32 scalp electrodes, while fMRI scans were simultaneously acquired with a 1.5-Tesla magnetic resonance imaging (MRI) scanner. After recording sessions and MRI artefact removal, EEG data were analyzed offline. We compared blood oxygen level-dependent (BOLD) signal changes on fMRI with EEG recordings obtained at rest and during activation (with and without focal interictal slow-wave discharges). Results: In 15/16 patients, when the EEG tracing showed the onset of focal slow-wave discharges on a few lateralized electrodes, BOLD-fMRI activation in the corresponding brain area significantly increased. We detected significant concordance between focal EEG interictal slow-wave discharges and focal BOLD activation on fMRI. In patients with lesional epilepsy, the epileptogenic area corresponded to the sites of increased focal BOLD signal. Conclusions: Even in patients with partial epilepsy whose standard EEGs show focal interictal slow-wave discharges without spikes, EEG-fMRI can visualize related focal BOLD activation thus providing useful information for pre-surgical planning.