Abstracts

Rationale: The intracarotid amobarbital test (IAT) is the most widely used procedure for pre-surgical evaluation of language lateralization in epileptic patients. However, a lot of limitations are associated with this invasive technique, especially in children. Functional magnetic resonance imaging (fMRI) is increasingly employed as a non-invasive alternative. Again, this method is more difficult to use with young children, especially hyperactive ones, since they have to remain motionless during data acquisition. The aim of this study was to determine whether near infrared spectroscopy (NIRS) can be used as an alternative technique to investigate language lateralization in children and special populations. Unlike IAT, NIRS is non invasive. As fMRI, it measures hemodynamic phenomena, but it is more tolerant to movement artefacts. We also report here our results obtained in a young epileptic child by combining NIRS with EEG video-monitoring to evaluate the potential of this combined technique to improve the epileptogenic zone localization in presurgical assessment.Methods: NIRS data were acquired in five epileptic children, a 12-year-old boy with pervasive developmental disorder and a 3-year-old healthy child as well as three healthy and two epileptic adults while they performed a verbal fluency task and a control task. When applicable, the results were compared to the subjects’ fMRI and/or IAT findings. Furthermore, one of the epileptic children, a 10-year-old boy, underwent a prolonged EEG-NIRS recording using fourteen EEG electrodes and 128 NIRS channels in order to localize his epileptogenic zone. Results of this continuous recording were then compared to those obtained with typical presurgical assessments (including SPECT, PET, MRI, EEG, EcoG) as well as more recent techniques (simultaneous EEG-fMRI and combined EEG-MEG).Results: During the verbal fluency task, clear laterality of speech was obtained in all participants, including the two non-epileptic children, and NIRS results matched fMRI and IAT findings. Electrical results from EEG-NIRS recording performed in the epileptic child showed ictal rhythmic spikes over the right frontocentral region. Ictal NIRS mapping co-registered onto the MRI revealed a high increase of rCBV over the right frontal region. This was in good concordance with other functional techniques (PET, SPECT, EEG-fMRI, EEG-MEG). A milder bilateral rolandic activation was seen with both NIRS and EEG-fMRI.Conclusions: These results, if replicable in larger samples, are encouraging and suggest that NIRS has the potential to become a viable, non-invasive alternative to IAT and fMRI in the determination of speech lateralization in children and clinical populations that cannot be submitted to more invasive techniques. Moreover, continuous EEG-NIRS has the potential to contribute favourably to the localization of the epileptogenic zone. Combined with classical and other novel non-invasive techniques, EEG-NIRS may reduce the need for invasive monitoring in non-lesional patients.