Preparing the ethical future of deep brain stimulation

Abstract

Background

Deep brain stimulation is an approved and effective neurosurgical intervention for motor disorders such as PD and ET. Deep brain stimulation may also be effective in treating a number of psychiatric disorders, including treatment refractory depression and OCD. Although DBS is a widely accepted therapy in motor disorders, it remains an invasive and expensive procedure. The ethical and social challenges of DBS need further examination, and discussion and emerging applications of DBS in psychiatry may also complicate the ethical landscape of DBS.

Methods

To identify and characterize current and emerging issues in the use of DBS, we reviewed the neurosurgical literature on DBS as well as the interdisciplinary medical ethics and relevant psychological and sociological literatures. We also consulted the USPTO database, FDA regulations and report decisions, and the business reports of key DBS manufacturers.

Results

Important ethical and social challenges exist in the current and extending practice of DBS, notably in patient selection, informed consent, resource allocation, and in public understanding. These challenges are likely to be amplified if emerging uses of DBS in psychiatry are approved.

Conclusions

Our review of ethical and social issues related to DBS highlights that several significant challenges, although not insurmountable, need much closer attention. A combination of approaches previously used in neuroethics, such as expert consensus workshops to establish ethical guidelines and public engagement to improve public understanding, may be fruitful to explore.

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.