| Epilepsy is a neurological disorder that affects 0.5 to 1% of Canadians. Treatment implies long-term drug therapy, to which approximately 30% of patients do not respond. For these patients surgery may be considered. The goal of surgery is the resection of brain tissue that contributes to generate seizures, without causing functional loss. During pre-surgical evaluation, multimodal non-invasive imaging is performed to localize brain areas involved during the generation of seizures, i.e., the epileptic focus, but also other areas generating epileptic discharges with no clinical manifestations, the Interictal Epileptiform Discharges (IEDs). IEDs are transient abnormal waveforms characteristic of the epilepsy of each patient one can measure using scalp Electroencephalogram (EEG). Functional Near infrared spectroscopy (NIRS) acquired simultaneously with EEG is a new promising technique to study hemodynamic responses at the time of epileptic activity. NIRS can monitor local fluctuations of deoxy and oxy haemoglobin concentrations within 1cm of cortex depth and with excellent temporal resolution. NIRS is therefore the ideal complement to simultaneous EEG/ functional magnetic resonance (fMRI) imaging technique. In order to characterize brain areas involved in the generation of seizures and IEDs, this project aims at setting a complete environment for data acquisition and analysis of simultaneous EEG/NIRS data. Our objective is to demonstrate the clinical relevance of this technique during the presurgical evaluation of epileptic patients. The first step of this project will consist in the development of a cap enabling a quick and safe positioning of NIRS optodes and EEG electrode. The second step will consist to validate two detection methods of the hemodynamic response. These methods are based on the general linear model but differ from the ones used in fMRI analysis, as they need to take into account the specificities of large physiological fluctuations observed in NIRS data. They will be evaluated in an environment mimicking the occurrence of epileptic activity. Some analysis on real data has also been done. |
