Abstracts

Rationale: Identification of the epileptic focus is the most important purpose of the presurgical evaluation in patients with intractable epilepsy. fNIRS is light based neuroimaging technology for continuous and non-invasive measurement of oxygenated (oxy-Hb), deoxygenated (deoxy-Hb) with high temporal resolution during long term video-EEG monitoring for epileptic patients. High tolerance of fNIRS against the head movement enables this method to be applied in recording during seizures. In the present study, we evaluated the feasibility of fNIRS in focus diagnosis in medically intractable epilepsy.Methods: fNIRS was recorded along with long term video-EEG monitoring for the cases who were applicants for epilepsy surgery. Fifteen partial seizures with/without generalize seizures in eleven cases were recorded. These cases finally underwent focus resection under the diagnosis of mTLE after other diagnostic procedures. 44 channel NIRS (ETG 4000; Hitachi Medical Corporation, Japan, wave length; 695 and 830nm) were used. We calculated the average value of oxy-Hb over 20 s from the fNIRS-defined epileptic onset. This value was determined for four channels and averaged between the channels in the same hemisphere. Then, averages for left and right hemispheres were compared. We determined that the side with the higher value was the focus side.Results: Increase of Oxy-Hb was observed after 10 to 30 seconds after the EEG onset.Deoxy-Hb increased simultaneously with Oxy-Hb in most of the cases. Focus side was determined by unilateral increase of 11/12 in OxHb and 9/12 in DeoxyHb on the correct focus side or location. Duration of fNIRS increase was shorter than the period with epileptic discharge observed on EEG.Conclusions: fNIRS is non-invasive useful tool for determining epileptogenic side of intractable MTLE patient.