Functional neurosurgical simulation with brain surface magnetic resonance images and magnetoencephalography.

We present a novel noninvasive technique for functional neurosurgical simulation combining three-dimensional magnetic resonance imaging of the brain surface with somatosensory evoked magnetic fields (SEFs) in a case of subcortical brain tumor. The preoperative analysis using this technique revealed that the central sulcus was located between the SEF source projected onto the brain surface and the tumor. At the time of surgery, the central sulcus was clearly identified by phase reversal of the cortical recordings of somatosensory evoked potentials. The actual cortical anatomy and the maximum somatosensory evoked potential location showed excellent agreement with the preoperative analysis of the brain surface magnetic resonance images and the SEF source. The subcortical tumor, which was barely identifiable without reliable functional cortical anatomy, was easily found in the motor area, just before the somatosensory evoked potential (and SEF) source. The potential clinical application of this technique is discussed.