Spinal cord injury (SCI) can result in neurogenic lower urinary tract dysfunction including neurogenic detrusor over-activity (NDO) and detrusor-sphincter dyssynergia (DSD). Exciting developments in spinal cord stimulation (SCS) have demonstrated potential to improve motor function. Transcutaneous SCS (tSCS) provides a non-invasive alternative to epidural SCS, and there is preliminary evidence to suggest it can modulate spinal networks involved in micturition. However, there is ambiguity regarding optimal electrode sites and stimulation parameters. The aim of this study was to investigate optimisation of electrode site and tSCS parameters for activation of sphincter and pelvic floor muscles and during the filling and voiding phase of the micturition cycle in people with spinal cord injury.

Ethical approval was obtained from the Research Ethics Committee. Participants were recruited if they had a supra-sacral SCI and proven NDO from their most recent urodynamics. During visit 1, 1ms tSCS pulses of increasing amplitude where administered at three randomised electrode sites; cathode between spinous process of T11-12, or L1-2, anodes at iliac crests or abdomen. External anal sphincter (EAS) and bilateral tibialis anterior EMG were recorded throughout. Optimal electrode site was selected based on motor-evoked potential response, and tolerance to stimulation. With electrodes placed at the optimal site, tSCS was applied in 5 s bursts at either 1, 15 or 30 Hz during voluntary pelvic floor contraction, relaxation and control. During visit 2, participants completed 6 cycles of urodynamics, one control cycle at the start and end, two cycles applying either 30 or 15Hz tSCS during bladder filling, and two cycles applying either 1 or 15Hz tSCS during voiding.

Six participants were recruited (4 male, 2 female), with mean age 50 +/- 20 years old. 4 had an incomplete cervical and 2 an incomplete thoracic SCI.  All participants tolerated the stimulation, and there were no adverse events. Optimal electrode sites were cathode L1-2, anode abdomen (n=2), cathode T11-12, anode iliac crest (n=2), cathode L1-2, anode iliac crest (n=1) and cathode T11-12, anode abdomen (n=1). Interim analysis of the EAS EMG recordings indicate that tSCS can facilitate voluntary pelvic floor contraction.

Preliminary analysis of EMG data indicates that tSCS may enhance voluntary contraction of EAS. In addition, tSCS during the filling phase may increase bladder capacity. Further analysis is on-going. tSCS is an exciting new development which may improve bladder and bowel function following SCI.

Our initial studies optimising electrode positioning and parameters will be used to investigate the use of tSCS in a further study combining it with pelvic floor muscle training.