Botulinum toxin type-A in therapy of patients with anismus

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.

This study was designed to evaluate the efficacy of botulinum toxin type-A (Botox) injection to the puborectalis muscle in patients with anismus.

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 injections1-5 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.

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.

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.