Pre- and intraoperative functional brain mapping and monitoring for brain tumor surgery

Abstract

We reviewed the present status of pre- and intraoperative functional mapping and monitoring for brain tumor surgery. Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) have become gold standards to identify the central sulcus with electrical stimulation to the median nerve and language lateralization using word reading or verb generation tasks. For white matter mapping, diffusion tensor imaging (DTI) -based tractography is the only technique available, which visualizes the eloquent subcortical fibers including the corticospinal tract (CST) and the arcuate fascicles (AF). Cortical somatosensory evoked potentials, motor evoked potentials (MEP) with cortical and subcortical stimulation, and awake craniotomy are available for intraoperative functional monitoring. There were strong correlations between stimulus intensity for MEP with the fiber stimulation and the distance between CST and the stimulus points. The results indicate that a minimum stimulus intensity of 20, 15, 10 and 5 mA had stimulus points of approximately 20, 15, 10 and 5 mm far from CST, respectively Subcortical electrical stimulation to AF consistently induced paranomia during awake craniotomy. These facts indicate that tractography is a reliable technique for brain tumor resection. Finally, even though fluorescent imaging has the potential to navigate us to the tumor border, it is still necessary to develop quantitative analyses for this technique.