Deep Brain Stimulation – A New Frontier in Psychiatryby Shaheen E Lakhan, MD, PhD, MEd, MS, FAAN | March 12, 2010
For as long as the brain has been seen as the site of mental activity, it has followed that altering brain function should be implemented to treat mental illness. Second generation antidepressants and psychotherapy are currently the least invasive ways of affecting brain function but they leave too many patients only partially improved, and have proved completely ineffective for some. Estimates of treatment unresponsiveness are unreliable, but 30% to 40% patients with depression and obsessive compulsive disorder (OCD) probably become treatment failures. For these patients, techniques like deep brain stimulation (DBS) provide a promising treatment alternative.
In the middle of the twentieth century, the lesioning of areas of the brain was discovered to be an effective treatment for certain movement disorders. Unfortunately, there were damaging side effects as a result of these lesions. In the 1980s, it was determined that the same effects could be accomplished by stimulating the tissue with electricity. DBS was approved by the FDA as a treatment for movement disorders in 2002. Although still in the research stage, DBS appears to also be a major advance in the treatment of OCD and treatment resistant depression (TRD).
Electrophysiology and modern imaging allow the very precise placement of electrodes. Response can be optimized by changing location and adjusting stimulus site parameters. Since the patient cannot detect the simulation, periods of active stimulation and sham (zero voltage) can be alternated to provide single or double-blind controls. After the sites and parameters for DBS are selected, the stimulator is placed under the skin, usually below the clavicle (collar bone), and connecting wires are run under the skin to the stimulating electrodes in the brain. Although the sites for stimulation vary, they basically fall into two groups: a basal ganglia group and a cingulate gyrus group.
Callaway and I systematically reviewed the literature on DBS for TRD and OCD. Our research findings were recently published in BMC Research Notes. While the number of cases was small — nine for OCD, seven for TRD, and one for both — these were extremely treatment-resistant patients. While not everyone responded, about half the patients did show dramatic improvement. Associated adverse events were generally trivial in younger psychiatric patients but often severe in older movement disorder patients.
While still in the research stage, DBS promises to be a major advance. Modern imaging methods allows precise placement of electrodes. Electrophysiological micro-recordings from implanted electrodes before and during stimulation aid in defining the electrode locations. Measurement of cerebral blood flow (CBF) before and after stimulation provides additional accuracy. Location and parameters of the stimulation can be changed to individualize and optimize treatment. Since the patient usually cannot detect whether stimulation is on or off, artificial stimulation can easily be used to deceive participants and provide a control condition. This ability to use patients as their own controls is a powerful tool for reducing placebo effects.
There are also ethical considerations of DBS that need to be carefully considered. Would all people have equal access to treatment? If not, who would determine when a depression is severe or unresponsive enough for DBS? If it proves effective, should we allow DBS to be used for neural enhancement and pleasure?
DBS is a very promising new development for the treatment of severe treatment-resistant depression and obsessive-compulsive disorder. So far the clinical samples are small, and some of the theoretical rationales are less than clear. Nonetheless, the results so far are very impressive, and it is certain that present shortcomings will be addressed in the near future.
Lakhan, S., & Callaway, E. (2010). Deep brain stimulation for obsessive-compulsive disorder and treatment-resistant depression: systematic review BMC Research Notes, 3 (60) DOI: 10.1186/1756-0500-3-60
Photograph by Francisco Garcia. © 2010 Francisco Garcia.
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