Improved Neurosurgery for Movement Disorders

A system that morphs brain images can considerably simplify a neurosurgical method called deep brain stimulation (DBS) that is gaining acceptance in the treatment of movement disorders, including stiffness, tremor, rigidity, and slowed movement, caused by neurologic disorders such as Parkinson's disease, dystonia, multiple sclerosis, and obsessive-compulsive disease.

DBS is a very long, complex, and costly procedure, which involves implanting electrodes deep in the brain. To improve the procedure, electrical engineers and neuroscientists at Vanderbilt University (Nashville, TN, USA) have designed a pilot guidance system that automates the most complex part of the procedure: identifying the correct location to insert the electrodes. To function properly, the electrodes must pass through small nuclei deep in the brain that are about the size of a pea and are not visible in brain scans or to the naked eye.

"The biggest problem with the procedure is that the surgeons cannot see the structure where they have to put the electrode and, as a result, they must spend a considerable amount of time searching for it,” said Dr. Benoit Dawant, professor of electrical engineering, computer engineering, and radiologic sciences at Vanderbilt University.

The computer-aided guidance system compensates for disparities in the three-dimensional (3D) brain structure of each patient, something very difficult for surgeons to do by themselves. It reduces operating times by increasing the chances that the surgeons start searching very close to the target. To develop the system, Dr. Dawant's team started with the brain magnetic resonance imaging (MRI) scans of 21 post-operative DBS patients. Next, the researchers developed an advanced, multi-dimensional technique for morphing one brain scan into another and used this to combine all 21 brain scans to form a reference brain atlas.

Once they developed the atlas, the investigators started testing how well it predicts the invisible target's location in new patients. They did this by morphing the reference brain, with its cluster of electrode positions, onto a scan of the patient's brain. They then selected a point in the center of the cluster as their predicted target location. In six implantations, Dr. Dawant's team provided predictions to colleagues when they were planning the procedure. In four cases, the surgeons used the system's prediction and found the target area in the first pass.