Deep brain stimulation (DBS) is a neurosurgical procedure that has received FDA approval as a treatment for essential tremor, Parkinson’s disease, dystonia, and obsessive-compulsive disorder. The procedure involves an implanted pulse generator (IPG) connected by a thin steel wire to a lead with multiple cylindrical band electrode contacts at the distal end. The electrodes contact specific anatomical structures within a patient’s brain. The IPG is usually implanted under the skin of the abdomen or the clavicle, and it sends programmable electrical stimulation pulses to a selected combination of output electrodes within the brain. Two of these device systems, or one device with two lead outputs, may be implanted to stimulate both hemispheres of the brain if a patient has bilateral symptoms.

Non-FDA approved uses of DBS include treatment for chronic pain syndromes, major depression, anorexia nervosa, Tourette’s syndrome, and epilepsy. The treatment has been met with great enthusiasm, and the frequency of adverse effects has decreased over the years. However, recent exploration of DBS and other related advances in neuroscience have shed light on various ethical and legal issues, especially as these advances are being considered for even more radical, non-approved uses such as cognitive enhancement and brain imaging by the judicial system.

These more radical uses of DBS have been spurred in part by recent developments by engineers at MIT. The stiff, steel wires currently used in DBS can damage tissue—causing inflammation and scarring—when implanted deep into patients’ brains. However, MIT researchers have created smaller and more flexible wires capable of not only stimulating brain tissue, but delivering drugs and recording brain activity simultaneously, while drastically reducing the side effects one would expect from a traditional metal implant.

This technological breakthrough involves first making a large cluster of regular-sized tubes (a “macrotube” or “preform” template) with several components. This includes materials for probing small subsets or even individual neurons, a light-transporting component to optogenetically activate specific cells of interest, and hollow tubes to deliver drugs. Using a “thermal drawing” process, the macrotube is literally stretched until the collection of wires and tubes is on the order of 400 micrometers—slightly wider than a human hair. The organization is maintained, but every component is scaled down. The new wire is 100–200 times smaller than the original macrotube and may improve scientists’ ability to observe how previously unexplored cells and circuits influence local and brain-wide dynamics and plasticity in real time. This, in turn, is central to understanding neuropsychiatric diseases and to developing smarter interventions to repair or even improve brain function.

With these bleeding edge developments, we must ensure informed consent is properly obtained in cases of DBS treatment for non-FDA-approved disorders given the possibility of patients’ understanding of the treatment and ability to consent changing due to disease progression or the treatment itself. In addition, we must ensure that research on neurosurgical cognitive enhancement involves bioethicists so that issues of access and distributive justice, as well as the long-term risks and costs, are adequately considered. Finally, fMRI and other technological advances in neuroscience hold great promise for use in courtrooms, but such advances may require additional research and testing before they can be used by judges and jurors.

In sum, advances in neuroscience offer new hope for individuals with debilitating neurological and psychiatric disorders, and treatments such as DBS represent vast improvements over their ablational and destructive surgical predecessors. However, health care providers, policymakers, and bioethicists must work together both to temper patient expectations of long-term symptom improvement in light of potentially unforeseen effects and to tackle the various ethical and legal challenges.

Neil Issar

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