Abstracts

Functional magnetic resonance imaging (fMRI) provides a noninvasive method to indirectly study neuronal activity in the brain. fMRI can detect the cerebral hemodynamic changes that occur during focal epileptic seizures. Thus, fMRI could be a useful tool to study the cortical and subcortical structures involved in seizure generation and propagation., Three patients who had seizures during scanning were studied. Patient 1 seizures started with a left hemibody somatosensory aura followed by clonic twitching of the left arm. Ictal-EEG showed rhythmic spikes over the right parieto-occipital region. SISCOM showed an area of hyperperfusion over the right perirolandic region. Invasive evaluation located the ictal onset zone over the right parietal region. A tailored resection was performed rendering the patient seizure free.
Patient 2 had a history of frequent epileptic auras related to paraneoplastic limbic encephalitis. His seizures were characterized by sensation of fear, abdominal discomfort, olfactory hallucinations, piloerection, urinary urgency and tachycardia. Ictal-EEG showed a right anterior temporal seizure onset. MR showed a right mesial temporal sclerosis. After an anterior temporal lobectomy the patient was experiencing rare auras.
Patient 3 was a 37 year-old woman with right mesial temporal lobe epilepsy who had frequent psychic auras (déj[agrave] vu) after a right selective amygdalohipocampectomy.
Functional imaging was performed using a 1.5 T GE Signa LX. In all three patients, continuous whole brain EPI-BOLD volumes were acquired until a seizure was observed. Images were preprocessed and analyzed using the SPM99 package. Sequential block design analysis was carried out. For each voxel, we identified BOLD signal changes by calculating the percent signal change from the voxel baseline for each timepoint., Patient 1. The first signal change was located over the right parietal region with an excellent anatomical correlation with the ictal hyperperfused region showed by SISCOM as the ictal onset zone located by subdural electrodes. Afterwards, signal changes were seen in the perirolandic area, the ipisilateral thalamus, the cingulated gyrus, the mesial temporal region and the frontal region bilaterally.
Patient 2. The first BOLD-signal change was seen 50 seconds before the clinical seizure onset. It was located over both mesial temporal regions although more marked over the right temporal lobe.
Patient 3. Three typical seizures were registered. These started with a decreased in BOLD-signal over the right mesial temporal region followed by a marked increased in signal change over both mesial temporal regions more marked over the right mesial., Ictal-fMRI might enable us to get an insight into the complex process and dynamic interactions involved in seizure generation and propagation. In selected patients, fMRI could be an unvaluable non-invasive tool to determine the ictal onset zone.,