Medical University of South Carolina announced the results of a functional MRI (fMRI) study examining the effects of VNS (Vagus Nerve Stimulation) Therapy for patients with treatment-resistant depression (TRD).
The study, led by Ziad Nahas, M.D., associate professor, MUSC Department of Psychiatry, appears in the August 2007 issue of peer-reviewed Neuropsychopharmacology. The results show that VNS Therapy modulates areas of the brain that control mood. The researchers also identified variables, such as length of use, strength of stimulation and level of depression, to better understand the impact of VNS Therapy.
"These data provide further insight into VNS therapy's distinct mechanism of action and support its previously demonstrated long-term, sustained efficacy," Nahas said. "We are encouraged to see the unique benefit VNS therapy may bring to patients with one of the most difficult-to-treat forms of depression and are excited to continue neurostimulation research at MUSC."
The study illustrates that VNS Therapy modifies activity of the medial prefrontal cortex, the same area of the brain targeted by many antidepressant medications and electroconvulsive therapy (ECT). A critical time for such effective modulation occurs approximately at 30 weeks of treatment. Such modulation could support VNS Therapy's unique mechanism of action as a long- term treatment for chronic or recurrent depression and directly corresponds with the timeframe in which patients typically experience a decrease in symptoms. Further analysis of the data demonstrates that modulation of the brain is a dynamic process that over time leads to indirectly related improved response with continued use. These findings corroborate an earlier MUSC-led study that revealed approximately two-thirds of patients who respond to VNS Therapy continue to experience significant clinical benefit at 24 months, making VNS Therapy the only treatment for TRD to demonstrate such long-term improvements.
The FDA approved VNS therapy in 2005 as an adjunctive long-term treatment of chronic or recurrent depression for patients (18 years of age or older) who are experiencing a major depressive episode and have not had an adequate response to four or more antidepressant treatments. It is the only device ever studied and approved for treatment-resistant depression. VNS therapy is delivered from a small pacemaker-like device implanted in the chest area that sends mild pulses to the brain via the vagus nerve in the neck.
Nahas' esteemed colleague Mark S. George, M.D., MUSC Departments of Psychiatry, Neurology and Radiology, shares this vision and supports the need for additional research to maximize the potential of neurostimulation as a diagnostic and therapeutic agent. George has launched a new international, peer-reviewed journal that is dedicated to exploring the field of neuromodulation. Published by Elsevier, Brain Stimulation: Basic, Translational, and Clinical Research in Neuromodulation strives to provide the most comprehensive collection of research being conducted in this emerging field. As editor-in-chief, George's extensive experience researching neurostimulation applications will aide him in facilitating and shaping the field's promising future.