Accelerated (SNT) TMS: What's the Scoop?
TMS (Transcranial Magnetic Stimulation) has been gaining traction in modern psychiatry since its original approval by the US Food and Drug administration in 2008 for Major Depressive Disorder. Now with Deep TMS we have also gained additional approvals for Obsessive Compulsive Disorder, Anxious Depression, and Smoking Addictions. TMS holds a unique place in the treatment algorithm at The Anxiety Center as an attractive option for patients who have not found sufficient relief from more traditional pharmacological or cognitive behavioral approaches.
How does TMS Work?
TMS works by using powerful capacitors to create alternating currents within a coil that are able to generate a magnetic field; this field then causes a second inductance of inverted electric charge that is able depolarize neurons in a focal area of the surface cortex. The beauty of the treatment is that it is able to target the specific areas of interest in the brain and in turn, treat the psychiatric condition without all of the unwanted side effects caused by the more diffuse effects of medications.
SNT (formerly SAINT) Protocol
Many of us who closely follow psychiatric innovations are intrigued by a recent publication of double-blind randomized control trial found in the American Journal of Psychiatry. Dr. Nolan Williams and his team of researchers at Stanford University carried out an accelerated TMS protocol called Stanford Neuromodulation Therapy (SNT). In this study, Dr. Williams and his team were able to successfully condense what typically takes six weeks to complete into an intensive five day program. Not only that, but they achieved a staggering 79% remission rate among study participants.
In order to achieve these results they developed neuroscience-informed stimulation parameters for their TMS treatment. We know that connectivity research in Major Depressive Disorder shows that the dorsolateral prefrontal cortex becomes less active and fails to inhibit the subgenual cingulate. This network pathology is hypothesized to cause substantial cognitive impairment and inwardly directed negative thoughts. Research also indicates that negative connectivity between these two regions is positively correlated with TMS efficacy. Using the patient’s own resting state fcMRI images, the team at Stanford placed the TMS coil on their patient's scalp using neuronavigation equipment targeting the specific area of the left dorsolateral prefrontal cortex with maximum negative connectivity to the subgenual cingulate.
The treatment itself was delivered using the Localite neuronavigation system and MagPro X100 system. After that, patients were delivered either ten sessions of active or sham theta burst (iTBS). The iTBS included 50 Hz bursts with 2 second trains at 8 second intervals. The sessions themselves lasted a duration of 10 minutes or 1800 pulses. A total of ten sessions were delivered daily at 60 minute intervals. Stimulation itself was delivered at 90% of resting motor threshold (rMT) that was adjusted for depth. Given that the strength of electric field created by the TMS coil decreases with depth, depth-corrected intensities were estimated for what would have been equivalent to a 90% rMT.
Was the treatment safe?
Based upon the limited data available from this study and other accelerated TMS studies, there do not appear to be any significant safety concerns outside of the typical limited localized side effects, such as mild headaches. In fact, one interesting outcome was that there were some cognitive improvements seen after the study that were likely due to the reduced depressive symptoms.
Can I get the SNT protocol?
As with any exciting new research we can understand why patients who have failed standard treatments might be eager to try this treatment. We are currently working with our medical advisers to determine if and when it would be appropriate for us to attempt this treatment, given that it still should be considered experimental because of the lack of replications of the study and the limited number of participants. We remain cautiously optimistic that these results will stand in replications and studies conducted with higher statistical power. Additionally, fcMRI’s are mostly available in research capacity, so coil placement would likely need to be derived using neuronavigation estimates. Currently, we do not know how this would affect the treatment outcomes.