Long Term Efficacy of Deep Brain Stimulation

New long term data on efficacy of deep brain stimulation for treatment resistant depression are available. The first follow up data up to 1 year were already promising. Published research about deep brain stimulation for treatment resistant depression showed that six months after surgery, 60% of patients were responders and 35% met criteria for remission, benefits that were largely maintained at 12 months.
The average response rate to DBS after two and three years were 46,2% and 75%. More than one-third of patients were in remission at year 3. But what’s more convincing functional impairment in the areas of physical health and social functioning progressively improved up to the last follow-up visit.

The Mayberg group published a follow up for 6 patients after 6 months and they subsequently reported on 12 month outcomes in an expanded sample of 20 patients. The last report at 3 years of follow-up as summarized above were also with 20 patients. The report on the extended follow-up of these 20 patients results from data from 3 to 6 years (mean=3.5 years) after DBS implantation. The mean duration of follow-up of the 20 patients was 42,1 months. In general patients required less medication after DBS implantation.

Adverse events
Two patients died by suicide during depressive relapses. This is of concern but stipulates the severity of the illness and it’s consequences. From the editorial:

One issue arising from this study requires special attention—that of suicide. Two of the 20 patients in this extended follow-up study committed suicide, and two others made suicide attempts. There is no evidence suggesting that DBS was related to these deaths. Rather, these suicides reflect the severity and seriousness of treatment resistant depression. In one of these patients there had been periods of sustained remission, but the patient relapsed and required a course of ECT prior to her suicide. The other patient had persistent suicidal ideation. These results underscore the high mortality in patients with treatment-resistant depression, even with careful and frequent monitoring by experienced and competent providers. It should serve as an impetus for us to continue to strive to develop new strategies to treat this patient population.

The first year three of the first six patients had hardware infections, no device related adverse events occurred after those three. Eight battery replacement surgeries were required during follow-up (mean time to battery replacement, 43.3 months).

Over the course of follow-up, eight patients were hospitalized for medical reasons on a total of 12 occasions. Half of these admissions were for psychiatric reasons (worsening depression, N=3; suicidal ideation, N=3), and the other half were for nonpsychiatric reasons

Other scarce reports on efficacy and follow up with DBS targeting other areas also show comparable results. Limitations of this study:
Open label, selected group of nonpsychotic unipolar depressed patients which leaves it unclear whether other forms of depression will also respond favorably.

Kennedy SH, Giacobbe P, Rizvi SJ, Placenza FM, Nishikawa Y, Mayberg HS, & Lozano AM (2011). Deep brain stimulation for treatment-resistant depression: follow-up after 3 to 6 years. The American journal of psychiatry, 168 (5), 502-10 PMID: 21285143
Hirschfeld RM (2011). Deep brain stimulation for treatment-resistant depression. The American journal of psychiatry, 168 (5), 455-6 PMID: 21536698