The organization of each person’s brain function controlling movement, sensation and language is unique. As a result, brain surgery may require mapping 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, called resection. The removal of brain tumors and areas of the brain causing seizures, or cortical resections, are delicate operations that often require mapping.
UW Medicine neurological surgeons use functional brain mapping to help them identify motor areas that control movement, somatosensory areas that control sensation, and expressive and receptive language areas that control talking and understanding speech.
The neurological surgeon uses this information to help find a balance between removing diseased tissue while minimizing damage to crucial brain functions. Figure 1
shows temporal lobe language sites.
An MRI scan is given before surgery. Data is collected and synchronized by a computer system that 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 identify 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. Then the patient is taken into the operating room and placed under anesthesia.
Functional mapping begins. Motor mapping and sensory mapping can be performed with the patient under general anesthesia. Language mapping requires the patient to be awake. 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.
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.
Language mapping starts after all anesthetic is stopped, and the patient is fully awake. This isn’t 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 to numb 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 tumor or the epileptic brain region is located and where important brain functions are located, the surgeon can formulate a strategy for removing the affected area, while maximizing the preservation of functional brain.
In Figure 3 of the brain during surgery, you can see the findings from mapping sensation, movement and language.
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. If all is going as expected, the patient is moved to the acute care floor the next day. A typical hospital stay is three to four days.
The patient and family return to the surgeon's outpatient clinic six 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 five to seven days.
Our goal is to provide safe, multidisciplinary compassionate care. The physicians serving on our specialized teams are also involved in medical discovery to ensure that patients benefit from state-of-the-art knowledge and procedures.
ConsiderationsFunctional 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.
EffectivenessFunctional brain mapping was originally developed for use during epilepsy surgery by UW Medicine neurological surgeon Dr. George Ojemann and colleagues. It 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, while 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. Risk factors include bleeding, infection, complications from general anesthesia, heart problems, lung problems, stroke, coma and recent injury to the brain.
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 used to provide optimal care. The rehabilitation medicine team becomes involved, providing speech therapy, physical therapy, occupational therapy and other services when appropriate to help patients improve the quality of their lives.
Risks of not having this treatment
Brain tumors grow. Without treatment, this growth can lead to worsened symptoms and make a tumor unsafe for surgery. Epilepsy surgery can stop medically intractable
UrgencyThere is no urgency associated with brain mapping. Surgery for brain tumors may be urgent or planned, depending on the symptoms and tumor size.