title: Sacral nerve stimulation changes rectal sensitivity and biomechanical properties in patients with irritable bowel syndrome.
abstract: BACKGROUND
  Sacral nerve stimulation (SNS) has been demonstrated to alleviate symptoms and improve quality of life in selected patients with irritable bowel syndrome (IBS). The mechanisms of action, however, remain unknown. The aim of the study was to evaluate the effects of SNS on rectal sensitivity and biomechanical properties in patients with IBS.
  
  
  METHODS
  Twenty patients with diarrhea-predominant (n = 11) or mixed (n = 9) IBS were treated with SNS in a controlled, randomized crossover trial. They were randomized to either 1 month of SNS (ON) or placebo (OFF) with the opposite setting for the next month. Sensory and biomechanical parameters were assessed by multimodal rectal stimulation at the end of each period. IBS-specific symptoms were evaluated at baseline and at the end of each treatment period.
  
  
  RESULTS
  Cold stimuli were better tolerated in the ON period (19.9 °C[± 0.6]) compared to the OFF period (21.8 °C[± 0.6]; p = 0.03). Significantly lower cross-sectional areas were needed to elicit sensory responses in the ON period (1545 mm(2) [± 95]) compared to the OFF period (1869 mm(2) [± 92]; p = 0.015). The association between reduced sensory threshold and improvement of constipation was of borderline significance (p = 0.05). Wall stiffness was significantly lower in the ON period (192 mmHg[± 10]) compared to the OFF period (234 mmHg[± 10]; p = 0.004). Reduced wall stiffness was significantly associated with improved overall GSRS-IBS symptom score (p = 0.01). Reduced sensory threshold to stretch (p = 0.02) and reduced wall stiffness (p < 0.001) were predictors of the GSRS-IBS symptom score.
  
  
  CONCLUSIONS
  SNS for diarrhea-predominant and mixed IBS relaxes the rectal wall, while making it more sensitive to stretch and less sensitive to cold. Reduced wall stiffness and increased sensitivity to stretch are associated with improved GSRS-IBS symptom score.
authors.affiliation: Department of Surgery P, Aarhus University Hospital, Aarhus, Denmark; Neurogastroenterology Unit, Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Fassov
authors.forename: C
authors.initials: C
authors.lastname: Brock
authors.forename: L
authors.initials: L
authors.lastname: Lundby
authors.forename: A M
authors.initials: AM
authors.lastname: Drewes
authors.forename: H
authors.initials: H
authors.lastname: Gregersen
authors.forename: S
authors.initials: S
authors.lastname: Buntzen
authors.forename: S
authors.initials: S
authors.lastname: Laurberg
authors.forename: K
authors.initials: K
authors.lastname: Krogh
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D018592:Cross-Over Studies; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D012007:Rectum / Q000294:innervation*; D012684:Sensory Thresholds; D055815:Young Adult
keywords: irritable bowel syndrome; rectal biomechanical properties; rectal sensitivity; sacral nerve stimulation