Suicide after successful deep brain stimulation for movement disorders

To the Editor: Burkhard et al.1 report a high rate of suicide in patients who received deep brain stimulation (DBS) implants in four different targets for three different indications. The conclusion that patients treated with DBS have an increased risk of suicide appeared inadequately supported by the evidence provided and prompted us to review our own series collected at the Besta Institute (table). Our data showed that there was not a nonspecific increase in the risk of suicide following DBS implants and suggest instead that psychiatric unwanted reactions occur following subthalamic nucleus, but not posterior hypothalamus implants. Only four of Burkhard’s patients had Parkinson disease (PD), and three of them had early-onset PD that was genetically determined in most instances. Early-onset PD has a strong impact on quality of life and a high incidence of depression (and possibly of suicides). Indeed, the early-onset PD patients of the Swiss series had depression and other signs of psychosis. Considering only PD patients included in the heterogeneous Swiss series, the rate of suicides is reduced to 2.8%, more than double that of another series of 77 PD patients treated in France with bilateral STN stimulation.2 There may be more than one reason why patients with movement disorders in southwestern Switzerland have a higher rate of suicide than expected. First, Switzerland has one of the highest suicide rates in Europe.3 Second, the patients enrolled in the Swiss study did not comply with current selection criteria for DBS, such as CAPSIT guidelines,4 which exclude PD patients with severe depression from undergoing surgical interventional therapies. All patients but one in the Swiss series had a previous history of severe depression, and two of them had suicidal ideations or attempts before undergoing surgery. A pre-morbid mood disorder is a predictor of lower outcome and of psychiatric complications following DBS in PD.2,5 In the Swiss series, four of the six patients who committed suicide had two DBS implants, which involve three surgical procedures (implant-explant-implant) and an undisclosed number of surgical tracks in each hemisphere. It is doubtful that such multiple sequences are representative of standard clinical practice. A combination of microscopic lesions in strategic brain areas may have contributed to the observed suicidal behaviors. Furthermore, three patients had dementia. There is insufficient information on their cognitive dysfunction and on changes in medication that may have affected the patients’ outcome.