Parkinson’s patients who undergo deep brain stimulation tend to gain a substantial amount of weight after the procedure, but until now, the reasons for this have remained unclear. Now a new Italian study reveals that the post-operative weight gain may be associated with several factors, including an increased desire for food, a certain level of impulsiveness in some patients, duration of the disease, and medication levels.
The findings are published in the scientific journal Cortex.
“The alteration of body weight is one of the potential complications of deep brain stimulation as a treatment of Parkinson’s disease,” said first author Marilena Aiello from the International School for Advanced Studies (SISSA).
“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 behavioural viewpoint”.
The study, conducted in collaboration with the Santa Maria della Misericordia University Hospital, involved 18 Parkinsonian patients who underwent deep brain stimulation and 18 healthy volunteers. The researchers monitored patients before and after the intervention, assessing cognitive, psychological, and behavioral aspects
“The patients have been assessed in three distinct phases: prior to the operation, five days after the operation, and three months thereafter. They were always under pharmacological treatment, gradually reduced, whereas, at the time of the latest survey, the stimulator, too, was active,” said Aiello.
Patients also completed questionnaires used at clinical level to assess their levels of depression, anhedonia (the inability to experience pleasure) and impulsiveness. In addition, they were asked to complete some tasks designed to assess their food-reward sensitivity and impulsive reactions to food.
“Our results have confirmed a significant weight gain during the months following the operation. 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,” said Aiello.
“However, we have also noted the importance of individual characteristics, such as attentional impulsiveness — i.e. the tendency to take sudden decisions — and of characteristics related to the disease, such as its duration and the reduction in the pharmacological load.”
Aiello adds that the findings confirm the multifactorial nature of postoperative weight gain and “offer important tools to identify the patients under greatest risk and accordingly prevent an excessive or anyway debilitating weight gain”.