Supplementary Motor Area as a Target Zone for Non-invasive Neuromodulation: a Systematic Review of Basic and Clinical Approaches

SMA as a target for repetitive TMS: a systematic review of basic and clinical approaches Introduction. Supplementary motor area (SMA) is a multifunctional cortical region [1], that is a promising target for neuromodulation in a wide range of neuropsychiatric disorders, affecting motor and cognitive domains [2]. Repetitive TMS (rTMS) of the SMA has been shown to improve motor symptoms in Parkinson’s Disease, Obsessive-Compulsive Disorder, Tourette’s syndrome etc. [3,4,5]. However, neither systematic review nor meta-analysis has been conducted on this topic. A current study is dedicated to cover this lack of knowledge and to provide an overview of the rTMS SMA studies in healthy volunteers and patients. Methods. This systematic review was conducted and reported according to the Cochrane and PRISMA guidelines (PROSPERO ID - CRD42020141289). All original articles published up to 27/072019, considering SMA rTMS were extracted from PubMed, Cochrane and Scopus databases. Three investigators assessed the studies’ quality with the Cochrane risk of bias tool [6]. 92 articles were divided into two categories: (1) studies in healthy volunteers and (2) studies including patients. The qualitative analysis was performed with narrative textual synthesis. The quantitative analysis performed using random-effects model for randomized, double-blinded, sham-controlled studies. Results. Literature analysis revealed the effect of the SMA rTMS neuromodulation on a wide range of the motor control aspects (movement preparation, sequence processing, breathing control), emotions and time processing. SMA rTMS caused clinical improvement in Parkinson’s Disease, Obsessive-Compulsive Disorder, and Tourette’s Syndrome patients. Meta-analysis did not statistically confirmed effectiveness of 1 Hz pre-SMA rTMS in Obsessive-Compulsive Disorder patients. Conclusion. Analysis of the SMA rTMS studies showed that SMA is critically involved in motor and cognitive processes. In a clinical setup, SMA seems to be an effective target for neuromodulation in patients with affected motor system. This review will be in help for new neuromodulatory protocols development. References: 1. Nachev, P., Kennard, C., & Husain, M. (2008). Nature Reviews Neuroscience, 9(11), 856–869. 2. Walther, S., Schäppi, L., Federspiel, A., Bohlhalter, S., Wiest, R., Strik, W., & Stegmayer, K. (2016). Schizophrenia Bulletin, sbw140 3. Shirota, Y., Ohtsu, H., Hamada, M., Enomoto, H., & Ugawa, Y. (2013). Neurology, 80(15), 1400–1405. 4. Gomes, P. V. O., Brasil-Neto, J. P., Allam, N., & Rodrigues de Souza, E. (2013). The Journal of Neuropsychiatry and Clinical Neurosciences, 24(4), 437–443. 5. Kwon, H. J., Lim, W. S., Lim, M. H., Lee, S. J., Hyun, J. K., Chae, J. H., & Paik, K. C. (2011). Neuroscience Letters, 492(1), 1–4. 6. Liberati, A., Altman, D. G., Tetzlaff, J., Mulrow, C., Gotzsche, P. C., Ioannidis, J. P. A., ... Moher, D. (2009). BMJ, 339(jul21 1), b2700–b2700.