Patrick J. Kelly

Information from magnetoencepalography (MEG), the noninvasive recording and analysis of the minute magnetic fields emanating from the brain, is entirely different from that provided by computed tomography (CT) or magnetic resonance (MR) imaging. The latter two provide anatomical information while MEG provides functional information. Because its time resolution (1 ms) is far superior, MEG
permits the brain to be observed "in action" rather than as a still image, therefore providing a tremendous asset to neurosurgical procedures. We use the MEG system housed in Dr. Rodolfo Llinás'' laboratory at NYU School of Medicine; it is one of six such systems in North America and the only one on the East Coast. Its primary use has been to study a wide range of neuroscientific problems.

With MEG, it has been suggested that synchronization of 40-Hz cortical oscillations may be responsible for binding sensory inputs to create a coherent internal perception of the external world. MEG also maps the human somatosensory and motor cortices, providing crucial information to a neurosurgeon planning a procedure near such an area because resection can cause loss of sensation or even paralysis. We collaborated with the MEG system group to integrate this technology with the COMPASS stereotactic system. We can now
plan the procedure so that the operative risk to these eloquent areas of the brain is minimized because the information interactively and intraoperatively helps determine the proximity of the scalpel to these important areas.

MEG will, in the near future, aid us in ascertaining not only how the normal human brain functions but also how the abnormal brain malfunctions; Parkinson disease studies are in progress. Combined with this basic science research, MEG integrated with image-guided stereotactic neurosurgery will some day allow the neurosurgeon to know which areas of an individual''s brain are responsible for
certain aspects of higher-level human functions. This will permit more accurate surgical risk assessment, better neurosurgical planning, and more strategic intraoperative guidance.