How Awake Brain Surgery Works

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Parkinson’s disease makes it hard to do many things that people without the condition take for granted. A disorder of the nervous system, Parkinson’s affects movement and often includes tremors—uncontrollable shaking of the hands or other body parts that can turn patients’ lives upside down, robbing them of the motion control they need to do their jobs, or simple tasks like brushing their teeth. Many patients can manage their tremors with medication, but for some, the treatment becomes less effective over time. There is hope. Deep Brain Stimulation (DBS) is a surgery that can—almost instantaneously in the operating room—stop the tremors. “It’s the use of stimulation within nuclei deep inside the brain to try to correct dysfunction within neurological circuits,” explains Jason Gerrard, MD, chief of functional neurosurgery at Yale. The procedure involves implanting one or more electrodes into specific areas in the brain associated with the movement disorder. The electrodes, controlled by an external stimulator, send electrical impulses that regulate abnormal or overactive impulses. “Early on, it was identified in Parkinson’s disease that neurons within the substantia nigra were being lost,” says Dr. Gerrard. “And these neurons were known to contain the neurotransmitter dopamine.” (Regions in this circuit were found to be overactive due to the loss of dopamine, which resulted in the motor changes—essential tremor—that Parkinson’s patients experience.) “And what we know from studying neurons is that if you stimulate neurons at a really high frequency, they lose their ability to fire. And by doing that, you can turn them off,” says Dr. Gerrard. In other words, DBS turns off the overactive neurons that are causing the tremors. During the procedure, which is performed on patients who are awake, the surgical team does real-time imaging and tests to be sure the electrodes are placed in the correct location. A few weeks after surgery, the patient’s external stimulator—a pacemaker-like device that is implanted under the skin in the chest—is switched on. “It’s very rewarding to see patients be able to return to being who they are,” says Dr. Gerrard.