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Peeling back the skull without a knife Understanding what transpires inside another person's head may be difficult for anyone, but for a surgeon about to operate on the brain, that knowledge can be a matter of life and death. New applications of functional MRI may make it a far less dangerous process. Neurosurgeon Dennis Spencer prepares to lay down a grid of electrodes on the exposed surface of the brain during a procedure that will map functional locations to be avoided during epilepsy surgery. Photo: Robert Lisak   For the past decade, patients undergoing brain surgery have benefited from a procedure pioneered at Yale. Before removing tumors, vascular malformations or other lesions that might cause seizure disorders, surgeons must carefully map the surface of the brain to pinpoint areas vital to language, and the organization of motor function, sensation and vision. Prior to surgery, the surgeon removes a portion of the patient's skull and lays a grid of electrodes over the cortex, the outer layer of gray matter at the brain's surface. The fully conscious patient then completes a series of tasks, during which critical regions of the cortex are identified and mapped as areas to avoid during surgery. The entire process lasts about a week and takes place in the Yale Epilepsy Unit. The map shown at left is produced from data gathered during a week of observation and EEG recording. The color outlines indicate areas of the cortex that control motor function (red), language and speech (yellow) and sensory ability (blue). The area outlined in black shows surgeons where they can most safely operate to remove the epileptic focus without causing a permanent neurological deficit. Spencer and colleagues are now using functional MRI studies like the one at right to map the brain non- invasively. Photo left: Kevin McCarthy. Photo right: Dennis Spencer   The chairman of the Department of Neurosurgery, Dennis D. Spencer, M.D., is exploring the use of the fMRI to achieve results superior to those from the electrode grid. A one-hour fMRI exam may eventually replace the week-long monitoring process that is now the state of the art, says medical physicist R. Todd Constable, Ph.D., an assistant professor who is working on the imaging technology with Dr. Spencer. To test this capability, the research team is correlating fMRI data with the already-proven electrode techniques. Says Dr. Spencer: "Surgeons will eventually be able to understand where language is controlled without having to invade the brain and physically map it."   < back | top of page | next >   Originally published in Yale Medicine, Winter/Spring 1998. Copyright © 1998 Yale University School of Medicine. All rights reserved.