Scientists at Mount Sinai have identified three important brain connections associated with long-term improvement in patients receiving deep brain stimulation (DBS) for severe depression that has not responded to conventional treatments. The discovery could help researchers make this experimental therapy more precise and effective.
Published October 1 in the American Journal of Psychiatry, the research examined the largest group of patients assembled across multiple independent cohorts to date who had received subcallosal cingulate deep brain stimulation (SCC DBS) for treatment-resistant depression.
The researchers found that lasting improvements were consistently associated with electrical stimulation reaching three specific white matter pathways: the cingulum bundle, forceps minor, and medial uncinate fasciculus/ventral amygdalofugal pathways.
These findings strengthen the case for using detailed maps of the brain's connections to determine exactly where electrodes should be implanted, rather than choosing their positions based primarily on anatomical landmarks. Known as connectome-based targeting, this strategy has already helped shape the ongoing Abbott TRANSCEND clinical trial, a randomized, controlled study that uses individualized brain connectivity maps to guide SCC DBS treatment.
"This study underscores the importance of individualized surgical targeting for achieving optimal outcomes with deep brain stimulation for depression," said Helen Mayberg, MD, Mount Sinai Professor in Neurotherapeutics and founding Director of the Nash Family Center for Advanced Circuit Therapeutics at the Icahn School of Medicine at Mount Sinai. "In any randomized controlled trial of a neuromodulation treatment, precise lead placement and confirmation that the intended brain target has been engaged are essential first steps. We still have much to learn about which patients are most likely to benefit from stimulation of this particular target, but developing imaging-based signatures that can match patients to their optimal treatment remains a central goal of our research."
How Deep Brain Stimulation Targets Severe Depression
For people with treatment-resistant depression, standard therapies have failed to provide adequate relief. Researchers are investigating deep brain stimulation as a possible treatment for individuals living with severe, persistent symptoms.
The procedure involves surgically placing electrodes inside the brain to deliver controlled electrical signals to circuits involved in depression. However, positioning the electrodes correctly remains one of the greatest challenges.
Electrical stimulation does not simply affect the brain tissue closest to an implanted electrode. It can also influence larger networks through the white matter pathways that connect different brain regions. As a result, two patients with electrodes implanted in nearly identical locations may experience very different outcomes depending on which connections are actually stimulated.
Earlier research from Mount Sinai and Emory University helped establish the importance of these networks. In studies published between 2014 and 2023 in Biological Psychiatry, Molecular Psychiatry, and Nature, the teams identified white matter pathways associated with successful SCC DBS treatment and developed a method for planning electrode placement using brain connectivity maps.
The latest investigation sought to determine whether those connections were also important in patients treated at other research centers. Scientists also wanted to understand whether differences in the pathways reached by stimulation could help account for patients who did not benefit.
Three Brain Connections Linked to Lasting Improvement
To investigate, the researchers examined information from several clinical studies, including the BROADEN trial and a patient cohort at the University of Toronto, where SCC DBS was originally developed.
They used computer models of the electrical fields generated by implanted electrodes alongside maps of brain connectivity. This allowed them to estimate which pathways received stimulation and compare those patterns across different patient groups.
The results showed a consistent relationship between sustained improvement and stimulation of the cingulum bundle, forceps minor, and medial uncinate fasciculus/ventral amygdalofugal pathways.
One finding was especially notable. Across the study sites, patients who had not responded to treatment after two years showed a lack of stimulation engagement with the left cingulum bundle.
The researchers did not investigate whether moving electrodes to reach this pathway would improve those patients' symptoms. Nevertheless, the pattern offers a possible explanation for why apparently similar electrode placements can produce different results. An electrode might be positioned in the correct general region but still fail to activate all the connections associated with lasting improvement.
"This study addresses an important question in DBS: not simply which area of the brain to stimulate, but which connections within that area need to be engaged," said Brian Kopell, MD, Director of the Center for Neuromodulation at Mount Sinai. "For a network disorder such as depression, millimeters can determine whether stimulation reaches the pathways we intend to modulate. Identifying and reproducibly engaging those pathways gives us a more precise surgical target and a framework for understanding why otherwise similar electrode placements may produce different clinical outcomes."
Source: ScienceDaily
No comments:
Post a Comment