Sex-differences in reported adverse side-effects caused by Deep Brain Stimulation therapy in the subthalamic nucleus

Abstract: Parkinson’s disease is a common neurological disease which will progressively damagedopaminergic neurons in the brain. Later stages of the disease will result in death of theneurons. The diagnosis is often made with respect to the motor symptoms, which includetremors, bradykinesia, and rigidity. In addition to motor symptoms, non-motor symptomsappear in many patients, such as cognitive changes and mood disorders. One method used totreat Parkinson’s disease is deep brain stimulation, where electric pulses are emitted to aspecific brain area. A common target is the subthalamic nucleus, which is part of the basalganglia. By using deep brain stimulation, the dose of other medications for Parkinson’sdisease can be lowered. However, the mechanisms of deep brain stimulation are not yetentirely known, and there have been many reports of adverse side-effects caused by thismethod, including depression and other types of mood changes. Even so, information of apossible sex distribution of these side-effects is still limited. Here, a qualitative essay wasmade where 16 articles describing reported side-effects in men and women were compared. Inaddition, unpublished data from optogenetic studies on male and female mice were analysedin order to examine putative sex-differences upon experimental brain stimulation strategies.The results from the optogenetics results did not show any statistically significant sexdifferences.In contrast, by comparing the selected articles in which results of deep brainstimulation treatment in patients were reported, some differences were found. First, it seemsthat women report more depressive-like symptoms than men. Second, while men also reportdepressions, they also report more aggressive behaviour upon the treatment. A preliminaryconclusion of this essay is therefore that certain sex-differences can be observed among theadverse side-effects reported upon deep brain stimulation in Parkinson´s disease. However,since the studied material was limited, more research is required to make firmer conclusions.