Deep brain stimulation raises special concerns because neuromodulation techniques deal with the direct stimulation of the brain. No other organ is so closely involved with concepts of mind or self, self-determination and consent.
POTENTIAL ALTERATION OF THE SELF. Interventions involving brain structure or function may result in alterations in cognition, memory, or emotions that may have a bearing on personhood. The potential of DBS to alter brain function may lead some to argue categorically against these interventions. This position would fail to appreciate that psychoactive drugs and cognitive rehabilitation alter brain states and that DBS can be used to restore brain functions that had themselves been altered by injury or disease.
The use of DBS as a potential agent of cognitive rehabilitation raises the question of whether helping a patient regain self-awareness is always an ethical good (Fins, 2000). Partial recovery of cognitive function could theoretically lead to greater awareness of impairment and increased suffering. These perceptions, which may also accompany improvement from more conventional rehabilitation, might be reversed with cessation of stimulation or be treated with antidepressant therapy.
THERAPEUTIC VERSUS INVESTIGATIONAL USE. Given the rapid development of this field, it is important to determine whether the application of deep brain stimulation to a particular disease is therapeutic or investigational. Historically, a treatment has moved from investigational use to therapeutic use when it is shown to relieve the symptoms it is intended to relieve with an acceptable degree of risk and when a significant proportion of physicians, especially those working in the field, are convinced that the intended outcome will appear without adverse long- or short-term effects that outweigh the benefits. This delineation between research and therapy has implications for the informed-consent process and the ability of surrogates to provide consent for DBS when a patient or subject lacks decisionmaking capacity. In the early twenty-first century DBS is recognized as therapeutic for the management of chronic pain, Parkinson's disease, and other movement disorders. It remains investigational for other indications.
Today, the use of a device such as the deep brain stimulator goes through several investigational stages before it is accepted as therapeutic. Formal mechanisms are in place to codify this transition. The FDA uses the investigational device exemption process to regulate devices that pose significant risk, such as the deep brain stimulator (Pritchard, Abel, and Karanian). FDA procedures, which supplement institutional review board (IRB) oversight of clinical trials, are designed to establish the safety and efficacy of devices and are required by law.
Once a device has been approved for use in humans, a clinical trial can proceed to assess the safety and efficacy of the device for a particular indication. Use of a device is deemed therapeutic when its safety and efficacy have been demonstrated in prospective trials, the most rigorous being ones that are double-blinded and randomized (a double-blinded study is one in which during the course of the study neither the subjects nor the conductors of the study know which subjects are in the active therapy or placebo group). Blinded studies can be conducted in the evaluation of DBS. Once the electrodes have been implanted, patients can be blinded to whether they are receiving stimulation, and their responses can be evaluated. Such methodological rigor is essential in the assessment of DBS because of the potential for a powerful placebo effect. The placebo effect has been shown to improve motor performance of patients with Parkinson's disease who were led to believe that they were being stimulated (Pollo et al.).
Demarcating the therapeutic use of DBS from the investigational may be difficult. For example, the use of an approved device does not, in itself, mean that an intervention is therapeutic. In these cases, the intent of the physician or clinical investigator may be important. Many would assert that if the physician's intent is to produce effects generally beneficial to the patient that have previously been demonstrated in similar cases, the intervention can be considered therapeutic. But when the investigator intends to use an approved device to increase knowledge of safety or efficacy for an approved indication or use the device at a new anatomical site or for a new indication, such interventions should be considered to be investigational and undergo review by an IRB.
Because investigational uses of DBS require more regulatory oversight, clinicians might be biased to classify borderline uses of DBS as therapeutic When it is unclear whether the use of DBS is therapeutic or investigational, clinicians should seek the guidance of their local IRB to mitigate this potential conflict of interest.
INFORMED CONSENT. The delineation of DBS as either therapeutic or investigational is also critical given ethical norms that govern informed consent. Given the ongoing investigational nature of many DBS procedures, potential candidates for stimulation need to be informed of whether the proposed procedure is therapeutic or experimental. Physicians who obtain consent from patients for therapeutic procedures should explain the risks, benefits, and alternatives so that the patient, or a surrogate authorized to consent for medical treatment, can provide consent.
Clinicians should seek to maintain the patient's voluntariness and ability to make an informed and reasonable decision about treatment with DBS. Those obtaining consent should appreciate that the chronic nature of the illness and desperation may lead a patient to consent to any treatment that promises symptomatic relief.
When individuals are approached for enrollment in an IRB-approved clinical trial, it is especially important to state the investigational nature of the intervention. Investigators should be careful to avoid the suggestion of a "therapeutic misconception" that falsely equates a clinical trial with safe and effective therapy (Applebaum et al.).
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