Electrical Stimulation of the Spinal Dorsal Root Inhibits Reflex Bladder Contraction and External Urethra Sphincter Activity: Is This How Sacral Neuromodulation Works?

Abstract

Introduction: Using a rat model, we aimed to confirm the inhibitory effect of dorsal spinal root (afferent) stimulation and test if bilateral stimulation is more effective than unilateral stimulation. External urethral sphincter (EUS) electromyography (EMG) is also assessed in conjunction with cystometrogram. Materials and Methods: Eighteen female Sprague-Dawley rats were tested following urethane anesthesia. Via urethral catheterization, the bladder was infused with normal saline to evoke rhythmic bladder reflex contractions (BRC). L6 spinal nerves were isolated and stimulated. Results: L6 stimulation was effective in inhibiting BRC. L6 bilateral dorsal root (DR) stimulation of 50% intensity was required to cause inhibition as compared to unilateral stimulation. In EUS EMG recordings, there was a strong association between EUS EMG activities and bladder contraction. When the bladder contraction was inhibited effectively by L6 DR stimulation, a considerable reduction was also found in the EUS EMG activities. Conclusions: L6 DR stimulation abolished BRC in our rat model. Bilateral L6 DR stimulation produced a 50% reduction in stimulation intensity, providing a similar BRC block. Abolishing BRC also appeared to coincide with a reduction in EUS EMG, implicating that sacral neuromodulation might act centrally, at least rostrally at the T8-9 spinal level.

Gentle Perineal Skin Stimulation for Control of Nocturia

“…In the CMG model, peripheral nerve stimulation to anesthetized animals prolonged the latency of urination, indicating an increased volume threshold of the micturition reflex (Su et al, ; Choudhary et al, ; Jiang et al, ; Kadow et al, ; Rogers et al, ; Bandari et al, ; Bansal et al, ; Fuller et al, ; Uy et al, ; Zhang et al, ). In the RMC model, peripheral nerve stimulation abolished periodic intravesical pressure changes, reflecting suppression of the micturition reflex at a volume that was previously supra‐threshold (Su et al, ; Kovacevic and Yoo, ; Su et al, ; Onda et al, ; Ren et al, ). Taken together, these findings indicate that electrical stimulation of peripheral nerves is capable of inhibiting detrusor muscle contractions.…”

“…In studies examining the effects of peripheral nerve activation by electrical stimulation on urinary bladder functions, stimulation is commonly applied to the tibial nerve, pudendal nerves, or the sacral nerves (Su et al, 2013a(Su et al, , 2013b(Su et al, , 2015Kovacevic and Yoo, 2015;Choudhary et al, 2016;Jiang et al, 2016;Kadow et al, 2016;Onda et al, 2016;Ren et al, 2016;Rogers et al, 2016;Bandari et al, 2017;Bansal et al, 2017;Fuller et al, 2017;Uy et al, 2017;Zhang et al, 2017). Hence, somatic afferents sending sensory inputs to spinal levels near pelvic nerve efferent outputs innervating the bladder are generally targeted for stimulation.…”

A Urodynamic Comparison of Neural Targets for Transcutaneous Electrical Stimulation to Acutely Suppress Detrusor Contractions Following Spinal Cord Injury

“…There have been several reports of improvement in LUT dysfunction using transcutaneous stimulation (Walsh et al, 2001;Barroso et al, 2013;Quintiliano et al, 2015) in addition to implantable devices, as well as a study reporting no effect on NDO in a small MS cohort. An acute inhibitory effect of SNS on NDO has been shown in several animal studies (Snellings and Grill, 2012;Su et al, 2012;Ren et al, 2016). Using non-invasive magnetic stimulation techniques, NDO has been acutely suppressed in humans with SCI (Sheriff et al, 1996), and interestingly, early application of implanted, continuous, SNS in the acute stages of SCI has prevented the development of NDO in the chronic phase of injury (Sievert et al, 2010).…”

“…Spinal Stimulation, using stimulation of the dorsal surface or dorsal roots of the spinal cord at the level of the T12 vertebra has had promising reports of improved lower limb and bladder control from both pre-clinical and clinical studies (Harkema et al, 2011;Hofstoetter et al, 2014;Gerasimenko et al, 2015;Gad et al, 2016;Ren et al, 2016;Herrity et al, 2018). Previous studies of epidural stimulation conducted with MS participants have reported acute improvements in LUT function (Meglio et al, 1980), including in the suppression of detrusor contractions with some carry-over effect noted.…”

Experimental Electrophysiological and Pressure Responses of Urinary Bladder Detrusor to Lumbar to Sacral Nerve Rerouting - An Animal Study with Negative Results

“…In addition to these classical approaches, efforts are being made to intervene closer to the cause by influencing the damaged innervation of the lower urinary tract [1]. Neurostimulation is understood as directly affecting the target organ, neuromodulation as affecting the nerve center by stimulating its afferent pathways and reinnervation as restoring nerve function with the aid of another, undamaged nerve.…”