Usefulness of arterial spin labeling and high density electroencephalography in the evaluation of complex partial seizures: a case study

Introduction: Epilepsy is one of the most serious neurological diseases. Perfusion sequences should be added in the epileptic protocol to improve the investigation of the focus and the correlated hemodynamic changes. Arterial Spin Labeling (ASL) was developed for the evaluation of cerebral blood flow (CBF) without contrast agents: the tracer is endogenous water in the blood, which is magnetically labeled [1]. Among scalp electroencephalography (EEG), the high density EEG (hdEEG) has showed a great accuracy for the source reconstruction [2]. Both tech- niques have been applied in this case study. Case: We report a case of a 35-year-old-man suffering from a drug-resistant focal epilepsy, with complex partial seizures in right temporal regions. He underwent right temporal lobectomy 5 years ago, but he still has seizures(1-2 per day). The recent Video-Stereo-EEG showed the continuous presence of epileptiform discharges, with spikes/multiple spikes over the right posterior temporal gyrus. The hdEEG recording was performed using 256 channels: during the regis- tration the patient had two prolonged seizures. Within 30 minutes (post-ictal period) he underwent to a 3T scan for the perfusion evaluation: a pulsed ASL sequence (Q2TIPS) with the PICORE labeling scheme was used [3]. Frontal, temporal, parietal and occipital lobes were considered, showing hy- perperfusion in the right temporal one. Temporal lobe also showed a marked perfusion asymmetry between right/left hemispheres (asymmetry index = 27%). High CBF values were found in the perilesional area and this was strongly concordant with the source localization from hdEEG. The mean CBF values for gray and white matter were respectively 49 ± 30 and 22± 18 ml/100gr/min. Instead, in the epileptic area around the resection the mean value was 107± 10 ml/100gr/min. Discussion: The post-ictal hyperperfusion found in this severe epilepsy was in accordance with previous results of literature, but usually coming from PET/SPECT studies with radioactive tracers[4]. We observed a correlation between regional CBF and scalp electrical activity. The combination of ASL and hdEEG provides a more precise and non-invasive localization of the epi- leptic focus. References: [1] Williams DS et al., 1992, PNAS, 89: 212-216. [2] Michel CM et al., 2004, Clin Neurophysiol, 115: 2195-2222. [3] Luh WM et al., 1999, Magn Reson Med, 41: 1246-1254. [4] Rowe CC et al., 1991, Neurology, 41: 1096-1103.