title: Prospective randomized double-blind study of temporary sacral nerve stimulation in patients with rectal evacuatory dysfunction and rectal hyposensitivity.
abstract: OBJECTIVE
  Prospective randomized double-blind placebo-controlled crossover trial of 14 female patients (median age 52 [30-69] years) with proctographically defined evacuatory dysfunction (ED) and demonstrable rectal hyposensitivity (elevated thresholds to balloon distension in comparison with age- and sex-matched controls).
  
  
  BACKGROUND
  Sacral nerve stimulation (SNS) is an evolving treatment for constipation. However, variable outcomes might be improved by better patient selection. Evidence that the effect of SNS may be mediated by modulation of afferent signaling promotes a role in patients with ED associated with rectal hyposensation.
  
  
  METHODS
  SNS was performed by the standard 2-stage technique (temporary then permanent implantation). During a 4-week period of temporary stimulation, patients were randomized ON-OFF/OFF-ON for two 2-week periods. Before insertion (PRE), and during each crossover period, primary (rectal sensory thresholds) and secondary (bowel diaries, constipation, and GIQoL [gastrointestinal quality of life] scores) outcome variables were blindly assessed.
  
  
  RESULTS
  Thirteen patients completed the trial. Following stimulation, defecatory desire volumes to rectal balloon distension were normalized in 10 of 13 patients (PRE: mean 277 mL [234-320] vs ON: 163 mL [133-193] vs OFF: 220 mL [183-257 mL]; P = 0.006) and maximum tolerable volume in 9 of 13 (PRE: mean 350 mL [323-377] vs ON: 262 mL [219-305] vs OFF: 298 mL [256-340 mL]; P = 0.012). There was a significant increase in the percentage of successful bowel movements (PRE: median 43% [0-100] vs ON: 89% [11-100] vs OFF: 83% [11-100]; P = 0.007) and Wexner constipation scores improved (PRE: median 19 [9-26] vs ON: 10 [6-27] vs OFF: 13 [5-29]; P = 0.01). There were no significant changes in disease-specific or generic quality of life measures. Eleven patients progressed to permanent stimulation (9/11 success at 19 months).
  
  
  CONCLUSIONS
  Most patients with chronic constipation secondary to ED with rectal hyposensitivity responded to temporary SNS. The physiological results presented support a mechanistic role for rectal afferent modulation.
authors.affiliation: Academic Surgical Unit, Centre for Digestive Disease, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom. c.h.knowles@qmul.ac.uk
authors.forename: Charles H
authors.initials: CH
authors.lastname: Knowles
authors.forename: Noel
authors.initials: N
authors.lastname: Thin
authors.forename: Katherine
authors.initials: K
authors.lastname: Gill
authors.forename: Chetan
authors.initials: C
authors.lastname: Bhan
authors.forename: Karyn
authors.initials: K
authors.lastname: Grimmer
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lunniss
authors.forename: Norman S
authors.initials: NS
authors.lastname: Williams
authors.forename: S Mark
authors.initials: SM
authors.lastname: Scott
mesh_terms: D000328:Adult; D000368:Aged; D002908:Chronic Disease; D003248:Constipation / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004599:Electric Stimulation Therapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D012002:Rectal Diseases / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D012447:Sacrum / Q000294:innervation*; D020886:Somatosensory Disorders / Q000150:complications / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome