German Team Refines Optimal DBS Target for OCD
by James Cavuoto, editor
July 2020 issue
As is the case with all forms of DBS therapy, success with DBS for obsessive-compulsive disorder depends heavily on the accurate placement of electrodes and requires millimeter-level precision. The optimal stimulation target for OCD has not been determined definitively. But a team of researchers in Germany recently reported progress identifying the optimal target.
Medtronic’s Reclaim DBS therapy received FDA approval in 2009 via the HDE pathway. The therapy is an alternative to anterior capsulotomy in patients who have failed to respond to three SSRIs. To date, the device has largely been used in clinical research settings since reimbursement is only available on a case-by-case basis. Investigators have looked at several different brain targets, including STN, VC/VS, and the anterior limb of the internal capsule.
A team of researchers from Charité – Universitätsmedizin Berlin recently reported significant progress in localizing electrode placement in OCD patients. Their findings, published in Nature Communications, identified a fiber tract which is associated with the best clinical outcomes following DBS.
The team studied 50 OCD patients who received treatment at a number of centers around the world. Using MRI imaging both before and after electrode placement, the researchers were able to visualize surrounding fiber tracts and test to see which of these the electrodes were selectively stimulating. “Our analysis shows that optimal results are linked to a very specific nerve bundle. Reliable evidence for this link was found across the cohorts of patients examined in Cologne, Grenoble, London, and Madrid,” said Andreas Horn, who led the Charité team.
The researchers initially examined two cohorts of patients, both of which received DBS to the IC or the STN. These brain structures have a variety of connections to other areas of the brain. They identified a specific tract situated between the prefrontal cortex and the STN as a suitable target for stimulation in both of these groups. Precise electrode localizations allowed the researchers to reliably predict treatment outcomes in both groups. These results were then replicated in two further, independent cohorts. When comparing their results with other studies, the researchers showed that the target areas described were also located within the tract-target identified in this study.
Describing the way in which these findings could help with electrode implantation, the study’s first author, Ningfei Li, said: “Our results do not alter the original target area, they simply helped us to define it more precisely. So far, we have had to steer our boat toward an island shrouded in fog. Now, we can make out the island itself and perhaps even the pier, so we can aim for it with greater accuracy.”
These findings could help Medtronic or other DBS system vendors expand the market for OCD. FDA approval via a PMA, rather than HDE route, could not only expand the addressable patient population, it could also lead to more universal reimbursement and perhaps a national coverage decision from CMS.