Functional Brain Mapping
Functional brain mapping is a technique used to identify areas in a person’s brain that control critical functions like vision, sensation, movement and language. These are often called the eloquent areas. Once the precise location and function of these areas are known, the neurosurgeon can create a custom map of an individual’s brain. The neurosurgeon can also map abnormal areas, such as those that produce seizures. During surgery, the neurosurgeon can use the map to preserve eloquent areas and remove abnormal areas.
Before brain mapping technology was available, neurosurgeons had to rely on a thorough but general understanding of the anatomy and function of the brain. But brains (like hands, faces, and all other parts of the body) follow a general anatomical plan with room for individual variation. With brain mapping, each person’s brain is treated as a unique landscape; the custom-made map allows the neurosurgeon to safely navigate around the borders of a given individual's eloquent areas.
This technique is also referred to as awake brain mapping or awake craniotomy, because the process of mapping the brain is done during surgery while the patient is conscious.
At Columbia University Irving Medical Center/NewYork-Presbyterian Hospital, we are proud to say our neurosurgeons are leaders in the field of brain mapping. They often teach courses and give lectures on this sophisticated technique, and their depth of knowledge and experience translates into excellent patient care.
When is Functional Brain Mapping performed?
Functional brain mapping may be performed when a brain lesion is near eloquent regions. In such situations, the risk of surgery can be loss of function in an eloquent region. Specifically, brain mapping may be used during surgery for epilepsy, brain tumors, or vascular malformations, such as arteriovenous malformation.
In addition, brain mapping can be used before epilepsy surgery if the seizure focus areas are unknown. Doing so allows the neurosurgeon to determine where the seizure focus area is so that is can be resected during epilepsy surgery.
Although beneficial in many situations, brain mapping is not the best option for everyone. Your neurosurgeon will discuss the procedure with you and answer any question you may have. Patients should have good general health and be able to stay calm during the awake portion of the procedure.
How should I prepare for Functional Brain Mapping?
Depending on the condition treated, a multidisciplinary team from the Columbia Comprehensive Epilepsy Center, Brain Tumor Center, or Columbia Cerebrovascular Neurosurgery Center will perform the brain mapping procedure. The team often consists of a neurosurgeon, neuroanesthesiologist, neuropsychologist and other health care professionals.
Brain mapping is performed either intraoperatively, that is, during surgery to treat a condition, or preoperatively, that is, before surgery to treat a condition. Preoperative brain mapping is only done for epilepsy if the seizure focus areas are unknown. The procedures differ slightly.
If brain mapping is done preoperatively, the patient is given general anesthesia and then Stereo EEG placement is performed. This is a minimally invasive technique in which a neurosurgeon creates a small opening in the skull and places thin electrodes in the brain. These electrodes will monitor electrical activity. The patient will remain unconscious throughout the operation.
After the operation, the neurosurgeon can stimulate the implanted electrodes while the patient is awake in order to map the seizure focus areas in the brain. Later, during epilepsy surgery, the neurosurgeon uses the brain map to locate and remove those diseased areas. The electrodes are also removed.
The patient does not experience pain during intraoperative brain mapping. The brain cannot sense pain, and the scalp, which can, is numbed.
To start, the patient is sedated and the scalp is numbed with a local anesthetic. Then the neurosurgeon performs a craniotomy, an open procedure involving the temporary removal of a section of skull.
With the skull open and brain exposed, the patient is woken up and brain mapping begins. The neurosurgeon stimulates eloquent areas of the brain with an electrical probe while the patient performs certain motor or language tasks, such as answering questions or trying to write. If the patient begins to struggle executing one of the tasks, the neurosurgeon knows to avoid that area of the brain because it controls critical functions. Based on the patient’s responses, the neurosurgeon creates a custom map of the functional areas of the brain.
Next, while referring to the custom map, the neurosurgeon carefully navigates to the brain lesion and treats it, preserving the function of the critical areas nearby. The neurosurgeon uses this map throughout the procedure.
Once the lesion is treated, the neurosurgeon replaces the skull bone and closes any incisions. The operation is complete.