Abstracts

Rationale: Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) superimposed on MRI (MSI) are being used in a growing number of centers as powerful tools for noninvasive cortical functional mapping as part of the pre-surgical evaluation of patients needing brain surgery. For young children, or children with neurological disorders affecting cognitive and behavioral functions, it may not be possible for them to understand the task or the necessity of being still. Our centers have developed a set of procedures that can be used to map functional areas of the brain in children who require sedation for their imaging studies, using passive activation of the cortical regions of interest in both MEG/MSI and fMRI. The procedures we have developed draw on research from healthy adult volunteers. Methods: We retrospectively reviewed our Epilepsy Monitoring Unit database for patients whom had fMRI and or MEG/MSI between September 2007 and May 2009. In children in whom both were done a direct comparison was carried out. In an ongoing analysis two measures are being evaluated: 1) Whether the peak bold signal on fMRI and the MEG/MSI dipole fall within the same gyral plane. 2) The distance of both measures from the central sulcus. Both active range of movement (aROM) in those able to cooperate and passive range of movement (pROM) in those unable to participate were done and is being utilized in the ongoing analysis. Though receptive and expressive language were assessed in cooperative patients, only sedated receptive language (sRL) was done in patients requiring sedation. Some cases required cortical mapping and a direct comparison was made betweeen these findings and the two modalities described above. Results: Ages ranged from 2 months to 18 years. 145 children received MEG’s (12 had repeat evaluations), language localization was accessed in 83 and motor testing in 26, most had SSEP’s and all had dipole localization. 45 children had fMRI’s, evaluating language, SSEP’s and motor. Active and passive motor and or language testing were carried out and a few children had both. No significant differences have been found between the anatomical distribution of active versus passive motor. 23 children had functional testing utilizing both modalities. These children are presently being compared using the two measures described above. An ongoing analysis have revealed a similar neuro-anatomical distribution in most children, however in 3 patients thus far, one technique was either unable to identify function or there was discordance seen. Conclusions: Though not yet concluded preliminary data suggests that both MEG and fMRI can be successfully used in both cooperative and sedated children of varying ages. Each modality has specific strengths and weaknesses and the choice of the technique used should be tailored to the underlying pathological process. By combining the two procedures, and utilizing passive activation of functional cortical regions we have been successful in identifying motor and or language in children being evaluated for epilepsy surgery.