The brain is the body's most complicated organ. Every area has a specific function. In the past, doctors had a rough map of the brain, but they didn't have the detail needed to be confident about avoiding harm to critical areas during surgery, nor a way to precisely navigate the unique layout of a specific patient's brain. For years, these complexities challenged neurosurgeons, especially when operating on brain tumors that were close to regions of the brain that control speech, movement or other key functions.

Fortunately, groundbreaking research at UCSF has led to advanced techniques for creating a map of an individual brain, allowing doctors to remove as much of a tumor as possible while minimizing the impact on important areas. We also use brain mapping to pinpoint and remove brain tissue that's triggering severe seizures.

Making the map

Mapping is done during surgery, using three-dimensional imaging technology that enables the surgeon to precisely target the area being removed.

Patients are fully anesthetized at the start of the surgery and then returned to consciousness after their surgeon has accessed the brain. Since the brain has no nerve receptors, patients may experience sensations but won't feel pain. Patients interact with the surgical team as the surgeon applies a small electrical current to areas of the brain surrounding the tumor. The patient's response helps the surgeon determine the boundaries of areas to avoid. For instance, because direct electrical stimulation of language areas temporarily disrupts language-related abilities, the operating team can test whether the patient is speaking and responding properly. If stimulation of a certain area interferes with the patient's ability to count, then that area is mapped as critical. Once these areas have been identified, the patient is put back under general anesthesia (made completely asleep) and the surgery is completed.