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 non-specific 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.
Table Clinical variables of patients who received DBS implants for PD or chronic cluster headache (CCH) at the Besta Institute
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.
Reply from the Authors:
We aimed to alert the medical community about DBS being a potential risk factor for suicide at a time when DBS is progressively becoming a routine procedure for advanced movement disorders, notably PD.1 This concern is shared by many other groups which have observed similar cases in their DBS cohort2,6–8 and requires extensive pre-operative evaluation and intensive psychiatric support in at-risk patients.9
We were interested to learn that Albanese et al. might be one of the few groups spared by this complication. In our patients, all but one suicide occurred between 2 to 7 years after the DBS procedure, suggesting that the follow-up of patients of Albanese et al. (PD: 3 years, CCH: 2 years) may be too short for such a complication statistically to occur.
Furthermore, with an estimated prevalence of one every 25 patients in our cohort, it seems clear that their yet unpublished CCH group (16 patients) is too small to substantiate the claim that posterior hypothalamus DBS is safer than STN. Finally, Albanese et al. are purposefully mixing patients with CCH and PD, forgetting that the psychodynamics of these two unrelated conditions may be enormously different.
The correspondence by Albanese et al. contains several errors. First, none of our suicide patients was demented, neither before nor at the time of death. Three PD patients exhibited mild neuropsychological abnormalities consistent with the underlying pathology, but did not fulfill the DSM-IV criteria for dementia. Second, as we discussed, no changes of stimulation parameters or medications occurred at or near the time of suicide. Third, while most patients had a past history of depression, none was severely depressed when assessed pre-operatively and all had low scores on the Montgomery and Asberg depression rating scale.10 All cases fulfilled the CAPSIT-PD4 guidelines at the time of evaluation, as required by our DBS program.
We were particularly interested in the 11% rate of transient hypersexuality reported by Albanese et al. This was only rarely observed in our cohort. Whether this unexpected reaction reflects a cultural trait, a bias related to authors’ domains of interest, or a true DBS-induced complication needs further investigation.
Disputes & Debates: Rapid online correspondence
NOTE: All authors' disclosures must be entered and current in our database before comments can be posted. Enter and update disclosures at http://submit.neurology.org. Exception: replies to comments concerning an article you originally authored do not require updated disclosures.
- Stay timely. Submit only on articles published within 6 months of issue date.
- Do not be redundant. Read any comments already posted on the article prior to submission.
- 200 words maximum.
- 5 references maximum. Reference 1 must be the article on which you are commenting.
- 5 authors maximum. Exception: replies can include all original authors of the article.
- Submitted comments are subject to editing and editor review prior to posting.