title: Sacral nerve stimulation at subsensory threshold does not compromise treatment efficacy: results from a randomized, blinded crossover study.
abstract: OBJECTIVE
  : Stimulation amplitude used in sacral nerve stimulation (SNS) is at or just above the sensory threshold (ST). This randomized, blinded crossover study aimed to document if stimulation at 75% or 50% of the ST would be as effective as stimulation at the ST for fecal incontinence (FI).
  
  
  METHODS
  : FI patients treated with SNS, who were satisfied with current treatment results and had a minimum symptom reduction of 75%, were eligible. Patients were randomized into 3 periods of 4-week stimulation: ST, 75% of the ST, and 50% of the ST. Patients completed a bowel habit diary and questionnaires on bowel functions and patient satisfaction at the study baseline and in each study period.
  
  
  RESULTS
  : Nineteen patients (18 females) with a mean follow-up of 51.7 ± 29.9 months were included from January to April 2010. The mean FI episodes per 3 weeks decreased from pre-SNS therapy 33.6 ± 31.6 to 1.1 ± 2.2 at the study baseline (P < 0.001). Decreasing the stimulation amplitude to as low as 50% of the ST did not affect the overall number of incontinent episodes (P = 0.078). The Wexner incontinence score dropped from 16.5 ± 2.5 for pre-SNS therapy to 7.4 ± 3.1 at the study baseline (P < 0.001). Decreasing the stimulation amplitude to ST, 75% of the ST or 50% of the ST, did not change the Wexner score when compared with the study baseline (P = 0.581). In general, patient satisfaction was high at the study baseline and did not deteriorate as the stimulation amplitude was decreased to 50% of the ST (P = 0.932).
  
  
  CONCLUSIONS
  : Subsensory stimulation as low as 50% of the ST is as effective as stimulation at or above the ST. The study was approved by the Regional Committee on Biomedical Research Ethics, Denmark, and registered at ClinicalTrials.gov (NCT01130870).
authors.affiliation: Surgical Research Unit, Department of Surgery P, Aarhus University Hospital, Tage-Hansens Gade, Aarhus C, Denmark. Jakob_Jakobsen@hotmail.com
authors.forename: Jakob
authors.initials: J
authors.lastname: Duelund-Jakobsen
authors.forename: Steen
authors.initials: S
authors.lastname: Buntzen
authors.forename: Lilli
authors.initials: L
authors.lastname: Lundby
authors.forename: Søren
authors.initials: S
authors.lastname: Laurberg
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D017060:Patient Satisfaction; D011788:Quality of Life; D012447:Sacrum / Q000294:innervation; D012684:Sensory Thresholds; D016896:Treatment Outcome