It’s easy to find a map of your town, your neighborhood, or your drive to work. But what happens if you need your brain mapped?
Neurosurgeons like Dr. McKhann often use brain maps during tumor or epilepsy surgery. Such maps are crucial when a surgeon’s instruments will be near “eloquent” regions of the brain. Eloquent regions control vital functions like language, movement, sensation or vision. Surgeons want to do as thorough a job as possible, but they don’t want to interfere with these eloquent regions.
In diagrams like the one above, eloquent regions look simple enough to locate. After all, they’re color-coded already. But in real life, brains aren’t color-coded, and everyone’s is slightly different.
So Dr. McKhann makes detailed maps of his patients’ brains—especially the eloquent regions close to the surgery site. Before the day of surgery, Dr. McKhann maps brain activity as his patients move, speak, look at pictures, or listen. (A patient’s task depends on what area needs mapping—e.g., a language area or a vision area.)
There are several non-invasive techniques for brain mapping before surgery:
Even though they’re all ways of measuring brain activity, each one has different strengths. For example, MEG has the potential to be more precise than EEG at pinpointing where something happens in the brain. And it can be more precise than fMRI at pinpointing when. But fMRI and EEG can “see” some areas of the brain better than MEG can. So the techniques are complementary and are often used together.
With the information he gathers from fMRI, EEG, and/or MEG, Dr. McKhann creates a digital map of the brain that he uses to plan his surgery.
But the mapping usually doesn’t end there. During “awake” surgery, he can refine that map even further.
In an “awake” surgery, the patient is conscious for certain parts of the surgery. The patient feels no pain, but is awake and can answer questions or follow instructions.
For awake surgery, Dr. McKhann uses a technique called electrocorticography (ECoG). This means he directly stimulates the brain with a small electrical current, one centimeter at a time. As he stimulates each area, the operating team asks the patient to perform certain tasks, like moving fingers or answering questions. When the patient starts to have trouble with his or her tasks, Dr. McKhann knows he has found the precise edge of the no-go area. He marks that on his digital brain map.
Few neurosurgeons used to specialize in these techniques. Today, they are becoming more widespread. Neurosurgeons see the incredible usefulness to patients. However, experience in these techniques is critical, particularly in the awake testing of patients in the operating room.
So it isn’t just patients who seek Dr. McKhann’s brain mapping expertise. He also helps educate his peers about these useful methods. For the last several years, he has co-directed an annual course for neurosurgeons called “Brain Mapping and Awake Mapping Techniques.” This spring, he co-directed the course in Washington, D.C. at the 83rd annual meeting of the American Association of Neurological Surgeons.
One goal of the course was for participants to become familiar with brain mapping techniques used before and during surgery—techniques like fMRI, EEG, MEG, and ECG, discussed above. Dr. McKhann and the course faculty educated participants about using these techniques, avoiding complications with them, and applying them to their daily practice.
At the same gathering in Washington, D.C., Dr. McKhann also served as faculty for a course on general advances in brain tumor treatment. It covered the last 12 months of medical and surgical advances, as well as the expanding roles for radiosurgery, molecular profiling, and functional brain mapping.
More recently, Dr. McKhann directed the course management of Brain Tumors in Eloquent Regions at the Congress of Neurological Surgeons in New Orleans in October.
Dr. McKhann is Florence Irving Associate Professor of Neurological Surgery and Director of Awake Brain Mapping for Tumors and Epilepsy.
Learn more about Dr. Sameer Sheth, another one of our neurosurgeons who specializes in brain mapping
Image credit: [Henry Gray (1825-1861)] / Anatomy of the Human Body
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