Researchers Discover Why Deep Brain Stimulation Causes Weight Gain in Parkinson’s Patients

Researchers have identified why patients with Parkinson’s disease gain weight after deep brain stimulation (DBS), a surgical procedure performed to treat their neurological symptoms and help control their movements.

They found that, after this procedure, patients have an increased desire for food and an increase in impulsiveness, which leads to weight gain. This outcome is also dependent on disease duration and reduction of drug treatment.

The findings, titled “Weight Gain After STN-DBS: The Role Of Reward Sensitivity And Impulsivity” and published in the journal Cortex, provide useful information to help doctors prevent weight gain in Parkinson’s patients receiving DBS.

DBS is a procedure given to Parkinson’s patients to treat their symptoms and help control their involuntary movements. A medical device called a neurostimulator is implanted in the brain to deliver electrical stimulation to the areas that control movement, thereby regulating nerve signals that cause tremors and other symptoms.

This treatment is usually recommended for patients whose symptoms are relapsing or worsening, and may be a useful complement to medication.

“The alteration of body weight is one of the potential complications of deep brain stimulation as a treatment of Parkinson’s disease,” Marilena Aiello, the study’s first author, said in a news release. “The origin was initially traced to the substantial reduction in motor symptoms, overlooking the role of the brain stimulation area — the subthalamic nucleus — in the reward system. Our intention was to assess the overall picture before and after the operation from a clinical as well as a cognitive, psychological and behavioral viewpoint.”

The study included 18 Parkinson’s patients receiving DBS treatment and 18 healthy controls.

“The patients have been assessed in three distinct phases: prior to the operation, 5 days after the operation, and 3 months thereafter,” Aiello said. “They were always under [drug] treatment, gradually reduced, whereas, at the time of the latest survey, the stimulator, too, was active.”

After DBS treatment, patients were asked to complete questionnaires about their levels of depression, anhedonia (inability to feel pleasure from enjoyable activities), and impulsiveness. They were also assessed in terms of food reward sensitivity and impulsiveness towards food. Results suggested that DBS activates the reward system, a brain circuit that, among other things, increases the desire for food.

“Our results have confirmed a significant weight gain during the months following the operation,” the researcher said. “In line with an alteration of the reward system, the weight variation has proved more consistent in those patients who, after the operation, have displayed an increased desire for food.

The team also observed the importance of individual characteristics, such as attentional impulsiveness — or the tendency to make sudden decisions — and of “characteristics related to the disease, such as its duration and the reduction in the [drug] load,” Aiello said.

The study identified several parameters that contribute to Parkinson’s patients’ weight gain after DBS, which can help identify patients at risk of excessive weight gain and prevent this outcome.