Botulinum toxin type-A in therapy of patients with anismus

INTRODUCTION: Anismus is a common cause of constipation and outlet obstruction: Standard therapy with laxatives or biofeedback has conflicting results. Surgical treatment gives poor results and has practically been abandoned. PURPOSE: This study was designed to evaluate the efficacy of botulinum toxin type-A (Botox®) injection to the puborectalis muscle in patients with anismus. METHODS: Twenty-five patients (15 females; mean age, 23.2) with history of constipation and symptoms of outlet obstruction underwent anorectal perfusion manometry and video-proctography. All patients were found to have a nonrelaxing puborectalis muscle on both modalities. All have been unable to expel a rectal balloon. Each patient who participated in the study was randomly assigned to undergo local injection of Botox - 10 units to each side of the puborectalis or 20 units to the posterior aspect of this muscle. Eight patients underwent further injections every 3 months in accordance with previous results. Follow-up was conducted 1, 4, 12, and 24 weeks after injection. Straining, anorectal pain, and overall satisfaction were assessed on a visual analog scale. Weekly evacuation, fecal incontinence, and complications were recorded. At the weekly meeting, each patient underwent anorectal manometry with a balloon expulsion test. RESULTS: Manometric relaxation was achieved after the first injection in 18 patients (75 percent). Once relaxation was achieved, it lasted throughout the follow-up. Nine patients (37.5 percent) expelled the rectal balloon after the first injection. Seven of 16 patients who failed the first injection had an additional one. In 2 patients it was successful (28.6 percent). Symptom improvement of 29.2 percent in straining index was recorded during follow-up. In 3 patients (12.5 percent) pain developed after injection. No other complications were observed. Overall satisfaction with Botox injection results was observed in 58.3 percent. CONCLUSIONS: Botox injection to the puborectalis muscle has been found to have a limited therapeutic effect on patients suffering from anismus. Our results justify the need for further double-blind placebo-controlled trials to determine the exact role of botulinum toxin type-A in anismus.