A recent report on 20 of the patients concluded that the benefit of DBS was long-lasting (Am. J. Psych. 2011;168:502-10).
"The average response rates 1, 2, and 3 years after DBS implantation were 62.5%, 46.2%, and 75%, respectively. At the last follow-up visit (3-6 years), the average response rate was 64.3%," wrote lead author Dr. Sidney Kennedy of the University of Toronto.
The present study raises some additional questions, said Dr. Lozano and his coauthors. Since the procedure was open label, the analysis cannot account for a placebo effect. Additionally, they said, disease heterogeneity, anatomic variation, and stimulation variants might play a part in which patients respond and which do not.
Nor is the SCG the only possible treatment target, they said. "It is clear that other brain targets may also be useful ... including the nucleus accumbens and the anterior limb of the internal capsule. The specific attributes and potential uses of each of these possible therapeutic targets will require much more investigation."
According to a press statement, St. Jude Medical, the company that created the DBS system in the study, is now conducting a similar study at 20 facilities in the United States and internationally, under a U.S. Food and Drug Administration Investigational Device Exemption.
Dr. Lozano disclosed that he holds intellectual property rights in the field of using DBS for depression and is a consultant for St. Jude Medical Inc. in Minneapolis, which developed the device used in this study.* Other authors indicated relationships with multiple drug companies. Dr. Burchiel reported having no disclosures.
*CLARIFICATION, 11/29/11: Information was added to clarify this sentence.