Studies have shown that certain brain functions are localized in specific areas of the cerebral cortex (brain surface). Nevertheless, because areas of the brain that control language and motor function may vary in exact location and are not visually distinct from other less critical areas, speech and movement are at risk of being compromised during some neurosurgical operations to remove brain tumors. Removal of such tumors could result in impaired speech or weakness of the opposite arm and leg. Neurosurgeons at RPCI use cortical mapping to define speech and motor areas of the brain in appropriately selected patients to reduce these risks, preserving the function of specific brain regions located close to the tumor.

Cortical mapping is especially useful during surgery on patients with certain types of gliomas and metastatic brain tumors. During cortical mapping, the patient remains awake and is without discomfort. The patient can communicate freely with the surgeon and is asked to name a series of images shown on a computer screen while the neurosurgeon stimulates the surface of the brain with a weak electrical current. Based on the patient’s verbal responses during this process, the neurosurgeon can determine which areas of the brain control important functions such as speech. This cortical “mapping” process makes it possible to isolate the tumor and to preserve critical brain functions with greater certainty. Cortical mapping provides appropriately selected patients with an additional measure of safety during brain tumor removal.