Abstract
Background
Sacral nerve stimulation (SNS) can produce symptomatic relief in patients with faecal incontinence. Moreover, peripheral nerve stimulation has been shown to affect brain function. The aim of this study was to determine whether SNS might produce important changes in cortical activity linked to improved continence.
Methods
In an experimental study, ten women with intractable faecal incontinence (mean age 51ยท3 years) were serially mapped with transcranial magnetic stimulation before and immediately after 14 days of temporary SNS (15 Hz, pulse width 210 ยตs), and then 2 weeks later. Anal sphincter electromyographic responses were recorded to cortical stimulation of multiple points over a scalp grid covering the bilateral medial cortex. Continence scores, anorectal manometry and rectal sensitivity data were also collected.
Results
SNS improved global symptom scores in the majority of patients; mean(s.e.m.) continence scores fell from 16ยท9(1ยท6) to 10ยท6(1ยท8) (P = 0ยท042). Cortical mapping showed a consistent decrease in corticoanal representation and overall excitability immediately after SNS compared with baseline (mean(s.e.m.) 38 083(13 669) versus 42 507(13 297) ยตV s; P = 0ยท017), which was reversed 2 weeks after SNS wire removal.
Conclusion
SNS produces symptom benefit in patients with faecal incontinence that is associated with a reversible reduction in corticoanal excitability. SNS therefore drives dynamic brain changes that may play a functional role in influencing anal continence.