The organization of each person’s brain function (e.g. movement, sensation, language) is unique. Because of this uniqueness, brain surgery may require “mapping” of these important functions to make surgery safer.

Functional brain mapping is often used for any condition that requires entry into the brain or removal of part of the brain (resection). The removal of brain tumors and areas of the brain causing seizures (cortical resections) are delicate operations that often require such mapping.

Neurosurgeons at UW Medicine use functional brain mapping to help them identify these critical regions:

• motor areas, which control movement;
• somatosensory areas, which control sensation
• expressive and receptive language areas, which control both talking and understanding speech.

The neurosurgeon uses this information to help him find a balance between removing diseased tissue while minimizing damage to crucial brain functions.  (Figure 1) shows temporal lobe language sites.

Prior to surgery, an MRI scan is given. Data is collected which is then synchronized to a computer system. This system allows the surgeon to make very precise images of the tumor and surrounding area.  Intra-operative ultrasound is used in conjunction with the MRI and operating microscope to delineate the shape and location of the tumor.

After MRI scanning, the patient is transferred to the pre-operative area, where IVs are started. The patient talks with the operating-room nurse and anesthesiologist to monitor responses to tests. From there, the patient is taken into the operating room and placed under anesthesia.

At this point, functional mapping begins. Motor mapping and sensory mapping can be performed with the patient under general anesthesia. Language mapping requires the patient to be awakened from general anesthesia. (The patient cannot feel pain from the operation during this brief period of consciousness.).

Sensory mapping is performed by electrically stimulating a nerve in the arm or leg and then recording the brain's response. This is called “somatosensory evoked potentials” or SSEP's.

Motor mapping is performed by using electrical current to directly stimulate the brain in order to elicit movement. Although the patient may be under general anesthesia, movements can still be evoked. (see Figure 1)

Language mapping commences after all anesthetic is stopped and the patient is fully awake. Why isn't this painful? Because the skull and the brain have no sensation. Only the scalp has sensation. After the patient is asleep, the surgeon injects local anesthetic (just like at the dentist) into the scalp. Once the patient is fully awake, the surgeon electrically stimulates the patient's brain, while the patient names objects presented on slides. When the area that is essential for language is stimulated, the patient is unable to name the presented object.

Electrocortiography is used to record the electrical activity from the surface of the brain. Figure 2 illustrates how the procedure can be used to identify epileptic areas (left image) and to determine the amount of current needed for electrical stimulation mapping (right image). Once the surgeon knows where the "bad stuff" is located, (the tumor or the epileptic brain region) and where the "good stuff" (important functional brain) is located, the surgeon can formulate a strategy for removing the affected area, while maximizing the preservation of functional brain.

In this photograph of the brain during surgery (Figure 3), you can see the findings from our mapping of sensation, movement, and language.

Post-operative surgery

Following surgery, the patient is transferred to the recovery room and the surgeon speaks with family and friends in the surgery waiting room. The patient is moved to the intensive care unit (ICU). If all is going as expected, the patient is moved to the regular floor the next day. A typical hospital stay is 3 to 4 days.

The patient and family return to the surgeon's outpatient clinic 6 to 10 days after surgery. During this visit, staples are removed from the incision and pathology is discussed. It is important to know that pathology results (which can reveal the type of tumor) take 5 to 7 days.

Our goal is to provide safe, multi-disciplinary, compassionate care. The physicians serving on our specialized teams are also involved in research to ensure that patients benefit from state-of-the-art knowledge and procedures.

Functional brain mapping should be considered for any patient undergoing brain surgery. This is to determine the proximity of the surgery to areas of the brain that are critical for function. Mapping can benefit surgery for brain tumors of all types and surgery for medically refractory epilepsy.

Functional Brain Mapping, originally developed for use during epilepsy surgery by UW neurosurgeon George Ojemann and colleagues, was created as a way to map the vital areas of each patient's brain in order to protect vital functions during surgery.

The brain mapping technique allows surgeons to remove larger amounts of the tumor than previously believed possible and avoiding the damage sometimes encountered in major brain operations. It also provides a window for seeing how the brain actually functions.

Brain mapping has few risks. The main risk, especially for people with epilepsy, is that a seizure may be triggered. Electrical discharges are closely monitored to prevent this from happening.

Risk will depend on the patient, the nature of the procedure and the location of the tumor or epileptic tissue to be removed. They include bleeding, infection, complications from general anesthesia, heart problems, lung problems, stroke, coma, and injury to brain near the surgery. Risks will depend on the patient, the nature of the procedure and the location of the tumor.

Every step is taken to minimize the risks of surgery, and though rare, surgical and postoperative problems are treated very seriously. When problems do occur, a team approach is usually used to provide optimal care. The Rehabilitation Medicine service becomes involved when appropriate, providing speech therapy, physical therapy, occupational therapy and other services that help patients improve the quality of their lives.

Brain tumors grow. Without treatment, this growth can lead to worsened symptoms and can make a tumor unsafe for surgery. Epilepsy surgery can stop medically intractable seizures. Without surgery, the seizures continue to disrupt and limit the patient's life.

There is no urgency associated with brain mapping.  Surgery for brain tumors may be urgent or elective (planned when convenient), depending on the symptoms and tumor size.