Acute lumbosacral nerve stimulation does not affect anorectal motor function in a rodent model

Area of Science:

• Neuroscience
• Gastroenterology
• Urology

Background:

• Sacral nerve stimulation (SNS) is a primary treatment for fecal incontinence.
• The precise mechanism by which SNS improves fecal incontinence remains unclear, particularly its impact on anorectal motor function.

Purpose of the Study:

• To investigate the acute effects of lumbosacral nerve stimulation on anorectal motor function in an animal model.
• To determine the impact on external and internal anal sphincter forces, rectoanal reflexes, and internal anal sphincter slow wave frequency.

Main Methods:

• Acute lumbosacral nerve stimulation was applied to 16 female rats.
• A novel in vivo preparation allowed simultaneous measurement of external and internal anal sphincter forces.
• Rectal distension was used to assess sphincter responses.

Main Results:

• Lumbosacral nerve stimulation at S1 or L6 did not significantly alter external or internal anal sphincter forces.
• Rectoanal inhibitory and excitatory reflexes remained unaffected by the stimulation.
• Slow wave frequency of the internal anal sphincter smooth muscle was not changed.

Conclusions:

• The study found no evidence that lumbosacral nerve stimulation directly impacts the motor pathways controlling fecal continence.
• Findings suggest that the therapeutic effects of SNS for fecal incontinence may stem from modulation of sensory feedback pathways.
• Enhanced sensory awareness of the pelvic floor is a potential mechanism underlying SNS efficacy.