Gevorg Eginyan’s MSc Thesis Proposal

Title: “Does Transcutaneous Tibial Nerve Stimulation Enhance Corticomotor Excitability of the Pelvic Floor Muscles?”

Supervisor: Dr  Tania Lam
Committee members: Dr Jean-Sébastien Blouin, Dr John Kramer

Background: Urinary incontinence negatively impacts quality of life for over 420 million people worldwide. The pelvic floor muscles (PFM) are crucial for maintaining urinary continence in humans. Transcutaneous tibial nerve stimulation (TcTNS) is used to manage urinary incontinence. However, the mechanisms of this treatment remain unclear. There is compelling evidence from upper and lower limb studies that peripheral nerve stimulation alone can trigger neuroplastic changes in primary motor cortex in the absence of motor training. Since the tibial nerve (L4-S3) shares segmental innervation with the pudendal nerve (S2-S4), which supplies the PFM, we hypothesize that TcTNS may lead to neuromodulation of the corticospinal projections to the PFM as well as Abductor Hallucis (AH) (innervated by tibial nerve). Thus, the purpose of this study is to evaluate whether TcTNS may alter corticomotor excitability of the PFM and AH when delivered at two different patterns on stimulation in neurologically intact individuals. Methods and Results: Healthy, able-bodied adults (18-40 years of age) will be recruited to attend 2 laboratory sessions over 2 days. TcTNS will be delivered either intermittently (trains of square wave 1-ms pulses delivered at 30Hz, 600 ms on and 400 ms off duty cycle for 60 min), or continuously (square wave 1-ms pulses delivered at 30Hz for 36 min). Stimulation conditions will be randomized and tested on separate days. Surface electromyography will be used to record motor evoked potentials (MEPs) from PFM and AH before and after stimulation. MEPs in the PFM and AH will be elicited by transcranial magnetic stimulation over the motor cortical areas controlling these muscles before and after TcTNS to compare the corticomotor excitability of these muscles. Preliminary results from one individual who completed the study protocol will be presented.