Hi, I'm Abhijit. I'm a research fellow at Mayo Clinic Neural Engineering Laboratories. I would like to thank the NNS Annual Scientific Meeting 2020 organizers for giving me the opportunity to present my work. I'm very excited to present the results of our study into the brain metabolic changes and clinical efficacy of transcutaneous afferent pattern stimulation for essential tremor patients. TAPS is a non-invasive neuromodulation therapy shown to be effective in ET subjects. This is a summary of our conflict of interest statement. Essential tremor is a debilitating condition affecting more than 7 million Americans. Pharmacotherapy is ineffective in 30-70% of these patients who need more invasive interventions such as deep brain stimulation or high-intensity focused ultrasound thermotomy. TAPS has emerged as a non-invasive neuromodulation option for such patients. It has been shown to reduce hand tremor in ET subjects. TAPS is delivered via a wristwatch-like device where two electrodes deliver alternating pulses of current to the median and radial nerve. This device also has an onboard accelerometer which measures tremor kinetics before and after each TAPS session. The mechanism of this therapy is not known. Therefore, we decided to investigate the impact of TAPS on brain metabolism over a 3-month period of use. We also investigated the effect of TAPS on tremor kinetics over this period of time. We enrolled 5 subjects in this pilot study aged 21 years or above who had been approved by the Mayo Clinic DBS Committee for DBS for treatment of essential tremor. The subjects were enrolled for a period of 90 days. On day 1, they underwent PET scan with 18-fluorodeoxyglucose ligand to establish baseline brain metabolism. Then they underwent device calibration and the first TAPS session. Tremor kinematics was recorded before and after this session. Then from day 2 to 89, they used the TAPS device twice daily at home along with the tremor kinetics recording. On day 90, they returned to the clinic for the second PET scan which was followed by the last 2 TAPS sessions. This is a summary of our results. Our subjects were 70 years of age on average with an average disease duration of 32 years. The compliance in our study was found to be 77.3 plus minus 25%. This is a summary of our PET-CT results. We observed significant increase in brain metabolism in ipsilateral cerebellum and a significant reduction in the metabolism of cerebellar vermis as well as ipsilateral and contralateral sensory motor cortices across the 5 subjects. This is a summary of our tremor kinetics results. The figure shows tremor kinetics recording for one of our representative subjects. The y-axis shows tremor power. The x-axis shows the days of use. Each blue and black dot pair represents one session. The black dot represent the tremor power before TAPS. The blue dot represent tremor power after TAPS. We observed a significant reduction in tremor power post TAPS compared to pre-TAPS across most sessions and in all 5 individual subjects. Our subjects experienced a median tremor power reduction of 50% or more. We observed no changes in the tremor frequency. To conclude, TAPS of the median and radial nerves was associated with metabolic changes in the cerebellum and other brain regions which are known to be involved in the tremor circuitry of essential tremor. Whether these changes play a causal role in the therapeutic effect or are epiphenomena remains to be determined. TAPS used consistently reduced tremor power. However, it did not affect tremor frequency. Continuation of this study and future invasive studies in patients and animal models of essential tremor would shed further light on the mechanism of this therapy. We have a few limitations including that this is an open-label study. Therefore, it is difficult to assess the contribution of placebo effect. However, successfully maintaining a comparable blind which mimics the device therapeutic effect at home is really challenging. The PET CT reflects a snapshot of time in the disease process and fluctuations in ET severity occur on a day-to-day basis. These fluctuations could be a potential source of bias in the brain metabolic changes observed in our study. A larger sample size showing a stronger strength of association could help overcome this bias. Therefore, we plan to continue our study in a larger cohort to confirm our preliminary findings. This is a summary of our references. I would like to thank members of the Mayo Neural Engineering Laboratories, members from Department of Radiology and Neurologic Surgery at the Mayo Clinic, and our collaborators at Kayla Health for their invaluable contributions to this research. If you have any questions, please feel free to reach out to me at bharat.abhijit at mayo.edu. Thank you.

Abhijit

Mayo Clinic Neural Engineering Laboratories

transcutaneous afferent pattern stimulation

essential tremor

neuromodulation therapy