Brain Mapping Provides Direction for Surgeons

Today, neurosurgeons are able to perform delicate and complex brain surgery that was impossible only a generation ago. A cutting-edge diagnostic procedure and guidance system called "presurgical brain mapping" is helping surgeons locate and remove tumors that once were considered inoperable, improving and saving the lives of many patients.

Presurgical brain mapping is a procedure with which John Ulmer, MD, has been intensely involved. Along with other researchers, he has refined and translated the technique for advanced uses in patients. Dr. Ulmer, a Professor of Radiology at the Medical College of Wisconsin, is a Functional Neuroradiologist and Chief of Neuroradiology Research in the Department of Radiology at Froedtert & The Medical College.

Presurgical brain mapping is used to create a computer-generated image of how brain activity is distributed, enabling surgeons to visualize key areas of the brain while planning surgery. The technique can be used as a guide for surgeons who are treating patients with certain types of brain tumors or epileptic seizures where diseased brain tissue is located close to areas of the brain that are critical to movement, vision, sensation, and language. Since brain tumors often occur in these important areas of the brain, the brain "map" can help surgeons preserve these vital areas while removing the maximum amount of the tumor.

Awake Surgery
Prior to the development of presurgical brain mapping, there was a greater risk for a patient to sustain neurological damage during surgery. Brain mapping can identify which areas of the brain control which functions. This valuable information is often used in conjunction with intraoperative brain mapping during surgery with the patient awake.

When neurosurgeons such as Wade Mueller, MD, use intraoperative brain mapping during "awake surgery," patients are sedated and given numbing medications so they feel no pain. During the procedure, the patient's head is placed in a fixed position to keep it still and ensure complete accuracy of the positioning during surgery. At a specific time during the procedure, the patient is awakened. "We want some patients to be awake during surgery so they can be tested and help the surgeon find and avoid different areas of the brain," Dr. Ulmer said.

While the patient is awake, the doctor uses special probes to stimulate different areas of the brain. At the same time, the patient may be asked to count, identify pictures or perform other tasks. The surgeon can then identify the area of the brain associated with each task. Guided by the preoperative and intraoperative brain maps, the surgeon removes as much of the damaged brain tissue as possible. "The goal of treatment is to attack the tumor without injuring the brain," Dr. Ulmer said.

fMRI and DTI
Functional MRI (fMRI) was pioneered in 1992 at The Medical College by biophysics faculty at the MACC Fund Research Center. The team was among the first three in the world to design systems for fMRI brain scanning. Dr. Ulmer joined the group in 1995.

While fMRI is a powerful tool that can be used to map the gray matter (the thinking part of the brain), it performs only half the job. Diffusion Tensor Imaging (DTI) is a new technique that can be used to map the brain's white matter, the wiring of the brain that communicates with the other parts of the brain and the body. DTI uses the diffusion of water molecules to image white matter connections in the brain. Water tends to diffuse more quickly along nerve fibers.

"Putting DTI and fMRI together allows the structure-function relationships to be tested more directly," Dr. Ulmer explained. "The two together are a very powerful pair, allowing us to map functional networks prior to surgery. "The techniques are used in an interdisciplinary process of collaboration. When a patient with a brain tumor comes in, he or she may see a Neurooncologist, a Neurosurgeon, a Functional Neuroradiologist, and a Radiation Oncologist. "In selected cases, I will see the patient for presurgical brain mapping, which will show any danger zones we must be aware of for the surgical approach," notes Dr. Ulmer. "We have outcomes data that are preliminary but incredibly promising."

Diagnostic Potential
"Brain mapping is definitely important for brain tumor patients, but it has huge potential for identification and monitoring of other conditions. Currently, it is being investigated to guide treatment for patients with atypical pain. We are mapping the brains of these patients and Dr. Brian Kopell, a neurosurgeon, places an electrode that stimulates the brain to help eliminate their pain," Dr. Ulmer said.

There are other uses for brain mapping, such as functioning as a diagnostic tool, according to Dr. Ulmer. "These are not clinical applications, but they can be helpful in understanding certain conditions," he said.

In the future, brain mapping may allow physicians to study recovery from stroke, and to study individuals with Attention Deficit Disorder/Attention Deficit-Hyperactivity Disorder (ADD/ADHD), Autism, Bipolar Disorder, and substance abuse. Physicians hope to be able to place patient-specific patterns into a database that compares them with normal patterns, allowing them to see how a patient's brain may differ from that standard. Based on these findings, physicians hope to gain insights that may improve treatment of these disorders and their behavioral implications.

Dr. Ulmer and his colleagues are cautiously optimistic that brain mapping, using the combined approach of fMRI and DTI, may also be used to help characterize Alzheimer's Disease. "Our hope is that it can be used for studying Alzheimer's and schizophrenia. There is exciting potential for this development, but it is not used to guide treatment at this point," he said.

Brain Tumor Program
The brain tumor program at Froedtert & The Medical College is recognized as among the best in the nation. "There are probably 350 malignant primary brain tumors newly diagnosed each year in all of Wisconsin, and we treat approximately 100 of them here," Dr. Ulmer said. "Because these patients can live normal lives for many years with their disease, preserving brain function is especially important. There are only two Neurooncologists (Hendrikus Krouwer, MD, PhD, and Mark G. Malkin, MD, FRCPC, FAAN) and one Functional Neuroradiologist in town, and we are all here. The breadth of the program is outstanding."

JoAnn Petaschnick
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.