Botulinum toxin type-A infiltration of the external anal sphincter to treat outlet constipation in motor incomplete spinal cord injury: pilot cohort study

Abstract

Background: Outlet constipation is a major problem in spinal cord injury (SCI) patients. We aimed to study the efficacy of external anal sphincter (EAS) infiltration with type-A botulinum toxin (BTX-A) in motor incomplete SCI patients with outlet constipation.

Methods: Double blind, randomized, placebo controlled, comparative study in 16 motor incomplete SCI subjects. Patients were randomly assigned toreceive100 UI of BTX-A (n = 9) or physiologic serum infiltration (n = 7) in the EAS under electromyographic guidance. Outcome measures included a questionnaire for clinical bowel function evaluation, colonic transit time and anorectal manometry. All assessments were done at baseline, 1 and 3 months after treatment.

Results: Fourteen patients completed the study. In the BTX-A group we observed an improvement of subjective perception of bowel function (p = 0.01), constipation (p = 0.02) and neurogenic bowel dysfunction score (p = 0.02). The anorectal manometry revealed are duction of EAS voluntary contraction pressure (p = 0.01). No changes were observed in the placebo group. No significant side effects were observed in none of the groups.

Conclusion: BTX-A infiltration of the EAS is a safe technique that in motor incomplete SCI, decreases the EAS contraction and the anal canal pressure during straining, and improves outlet constipation symptoms. Future studies in larger populations are needed.

Keywords: Spinal cord injury; botulinum toxin; constipation; neurogenic bowel; outlet constipation.