TechniquePreparing the ethical future of deep brain stimulation
Introduction
Deep brain stimulation is a form of neurosurgery that is now widely used to treat PD and is emerging as a potential treatment for some neuropsychiatric disorders [4]. Deep brain stimulation involves the implantation of at least one electrode, typically in thalamic, subthalamic, or ventral pallidus regions (for PD or ET), which is connected by very small wires and electrically stimulated by an IPG in the upper portion of the chest (subclavicular region). Deep brain stimulation was approved by the US FDA in 1997 for the treatment of tremor in ET and PD and in 2002 was more widely approved for the management of refractory PD. Deep brain stimulation is now an established therapy for PD and ET patients whose diseases are severe and drug refractory [26]. More than 35 000 patients worldwide have received DBS for those indications [39]. The current scientific and medical knowledge surrounding the mechanisms of action of DBS is still incomplete, but a widespread hypothesis is that DBS replicates the effects of neurosurgical lesioning [4]. In comparison to ablative surgery, DBS is considered reversible and nondestructive [42]. Other forms of neurostimulation techniques and devices currently used should not be conflated with DBS. Table 1 distinguishes DBS from 2 other forms of neurostimulation: VNS, whish is commonly used for the treatment of epilepsy, and TMS, which relies on the external stimulation of the brain to temporarily activate or deactivate cortical activity.
Recent studies claim that DBS is efficacious, and although not without major risks, it is relatively safe for the long-term management of severe ET, PD, and dystonia [10], [56]. Investigations of DBS in other motor and nonmotor conditions have emerged, in refractory depression, TS, OCD, chronic pain, and in multiple sclerosis [36], [46], [53] given the efficacy of DBS in PD and based on the undesirable irreversibility of ablative surgeries. Currently, there is an emerging literature documenting the efficacy of DBS in these disorders, and researchers have highlighted some potentially promising results [4]. In addition, case reports of DBS used to treat an anxiety disorder [40] and morbid obesity [28] have lead to unexpected results: relief of a comorbid alcohol dependence in the first case and memory enhancement in the second case (without any effects on the anxiety disorder or the obesity problem). In fact, a new clinical trial investigating DBS for memory improvement in patients with Alzheimer disease has emerged from the results of the second case study (NCT00658125, NIH clinicaltrials.gov). The number of clinical trials investigating DBS in established and emerging areas is likely to expand as trials already underway produce results over the coming years. Table 2 shows the current NIH-registered and completed clinical trials using DBS in neuropsychiatric conditions such as depression, TS, and OCD.
To realize the full potential of DBS, the ethical and social issues associated with this procedure must be addressed proactively. Some of these issues have already been acknowledged by leaders in the field of DBS neurosurgery [4] and neurosurgical ethics [16], [17], [19], [38]. In this article, we provide what to our knowledge is a first overview and discussion of current ethical and social issues in the use of DBS for PD and motor disorders including challenges in the identification of good surgical candidates, in health care resource allocation, and in conveying an appropriate public understanding about the procedure and its outcomes. We also comment, where appropriate, on the challenges related to the emerging uses of DBS in psychiatry. Our approach is based on the belief that identifying ethical and social issues now will contribute to further discussion and awareness in the future of DBS.
We reviewed the neurosurgical, neurological, and psychiatric literatures on DBS along with the bioethics, psychological and sociological literatures to identify and characterize the current and emerging ethical and social issues in the use of DBS. We also consulted the USPTO database, the US National Institutes of Health Clinical Trial database, FDA regulations and report decisions, and the business reports of key DBS manufacturers.
Section snippets
Patient selection: carefully identifying good candidates for DBS based on sound ethics and science
Selecting the appropriate candidates to undergo DBS is of fundamental importance. Established selection criteria should aim to identify candidates who will obtain and retain the greatest benefit from a DBS intervention and who are physically, cognitively, and emotionally capable of tolerating surgery and participating in their own postoperative care [41]. Being able to predict which patients are poised to achieve the greatest outcomes becomes important because first, the high costs of the
Informed consent: conveying risks and benefits to vulnerable and desperate patients and caregivers
Informed consent, that is, the patient or the authorized proxy's agreement based on a reasonable understanding and appreciation of the risks and benefits of a procedure, is a fundamental requirement of modern surgery and medicine. However, informed consent can represent a challenge because the disease process itself may impact cognitive function or disturb mood significantly [35]. For example, both in PD and in psychiatric disorders, deficits in executive function, attention, verbal fluency,
Resource allocation: facing the challenge of expenditures in underserved patient populations in overburdened health care systems
Deep brain stimulation devices and procedures cost tens of thousands of dollars [21], [25]. However, considering the burden of disease and cost of alternative best medical treatments, overall health care expenditures by patients may still be reduced by the DBS procedure. Several European studies have examined the direct costs (eg, cost of the surgical procedure, hospital stay) and indirect costs (eg, number of emergency department visits and neurological follow-ups) associated with DBS in PD.
Transfer of knowledge and public understanding: dispelling miracle-like stories, promoting balanced public information, and transfer of knowledge between health care professionals
Public understanding of the risks and benefits of the DBS procedure—like other medical technologies and procedures—can shape informed consent and expectations by patients and caregivers and may alter the reception of expanding clinical uses. One way that the public perception may be shaped is through media coverage of scientific advances and emerging therapies. Notable traits of media coverage of science and technology include failure to report important details such as cohort size and
Personhood, narrative, and identity: thinking ahead about a vastly extended use of DBS beyond the traditional framework of neurosurgery
Deep brain stimulation has an established efficacy in treating motor symptoms experienced by patients who have ET and PD, and this has lead to its overall acceptance and approval in these conditions. The long-term cognitive, psychiatric, and behavioral effects of DBS, however, are less well established, and studies are much more inconsistent in their conclusions about the effects of DBS on cognition and behavior in motor disorders. Often, an evaluation of these issues is complicated by the fact
Preparing the ethical future of DBS
Our review of ethical and social issues related to DBS highlighted that several significant challenges, although not insurmountable, need much closer attention. It is obvious that the realization of the full potential of this technique will require attention to a number of important ethical and social issues, issues that may be accentuated if DBS moves rapidly into psychiatric conditions. A combination of approaches previously used in neuroethics, such as expert consensus workshops to establish
Acknowledgments
Support for the writing of this article comes from the Institut de recherches cliniques de Montréal (ER, GM), the Fonds de la recherché en santé de Québec (ER), the Social Sciences and Humanities Research Council of Canada (EB), CIHR (NNF 80045, EB, ER) and CIHR New Investigator Award (ER). We would like to extend thanks to Nicole Palmour, Mary Pat McAndrews, Abbas Sadikot, and Lynette Reid.
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