Localization of eloquent area utilize to functional MRI in patients with brain tumor

It has become increasingly popular to use functional magnetic resonance imaging (fMRI) as a tool for preoperative functional brain mapping. We, however, have sometimes experienced the eloquent area (localized by fMRI), which did not match-up with the results from the intraoperative electrical cortical mapping. In this study, to clarify a reliability of fMRI, such cases were reported in detail and mechanisms would cause that phenomenon were discussed. Seventeen patients with brain tumor located in the region of motor and/or language cortex were investigated, and high dissociation between fMRI and electrical cortical mapping was noted in four cases. Of the four cases, two cases were reported their clinical course and studied the deoxyhemoglobin (Deoxy-Hb) consumption using near infrared spectroscopy (NIRS) during task performance. As a result, decreasing of Deoxy-Hb during the task was not shown. Blood oxygen level-dependent (BOLD) signals, which were observed in normal brain, would not be expected in the case where a brain tumor is close to the eloquent area. It suggests that fMRI cannot always localize the eloquent area in pathological brain. Therefore, care must be taken to adopt the information from fMRI, when operative strategy is going to be made.