To prepare for surgeries that target brain tumors or epilepsy, or for placement of devices such as a deep brain stimulation (DBS) implant, “awake” craniotomy is performed to determine which areas in the patient's brain are responsible for certain functions. In this procedure, surgeons electrically stimulate regions of the brain while the patient is awake, to create a map of areas that should be avoided during surgery, such as areas that govern speech and movement. This is a painless, but major, open brain surgery which can lead to excellent outcomes by preserving critical brain functions.
Most right-handed people are “left-brained,” meaning that speech and the understanding of words resides in the left hemisphere of the brain. The right hemisphere is most often associated with the ability to visualize in three dimensions, musical sense, and emotional response. While it is important to spare as much normal function as possible in any brain procedure, language is considered a very critical function, and thus much attention is paid to this ability when planning brain surgery. Movement is the other critical function, also controlled by very specific areas in both hemispheres- the left hemisphere controls the right side of the body, and vice versa.
Because the brain itself does not sense pain directly, an awake craniotomy can be performed while the patient is under local anesthesia. Awake craniotomy is major brain surgery that requires temporary removal of a portion of the skull to allow the surgeon access to the outer portion of the brain, or cerebral cortex. Because he or she is conscious during the procedure, the patient can report sensations in response to stimulation of specific brain areas. Sensations can be as specific as seeing an image (in response to stimulation of the visual cortex), to a feeling of déjà vu, to the movement of an arm or leg. These verbal reports and physical clues allow the surgeon to carefully plot a three-dimensional map of the brain and to pinpoint areas of disease or injury. Subsequent surgery can then minimize any damage to the brain that might compromise normal function.