Small Case Series Suggests Botulinum Toxin Affords Major Pain Relief in Endometriosis


TORONTO — Patients with endometriosis that is unresponsive to surgical and medical treatment may get relief from intravaginal injections with botulinum toxin, according to a case series from the National Institutes of Health.

“We saw an impressive period of relief beyond what we would expect,” said Dr. Melissa Merideth, an ob.gyn. with the Office of Rare Diseases at the National Human Genome Research Institute, an arm of the National Institutes of Health.

The study, which she reported in a poster at the annual meeting of the Society for Gynecologic Investigation, involved three women with chronic pelvic pain that persisted after laparoscopic excision of their endometriosis. Upon physical examination, all the women had palpable spasm of their pelvic floor muscles, Dr. Merideth said in an interview.

Because botulinum toxin relaxes muscle spasm and has been effective in the treatment of headache and myofascial pain, her group decided to test its effect on pelvic floor muscle spasm, she said.

“We felt the pelvic floor spasm was a component of their pain, and we wanted to see how addressing that would affect their other pain symptoms,” she said.

Working in an office setting in conjunction with a neurologist, a gynecologist injected a total dose of 100 U of botulinum type A toxin (reconstituted with 4 cc of preservative-free saline) transvaginally into between three and six injection sites in the women's levator ani muscles at sites of palpable spasm. The women were premedicated with Valium and the procedure was done using electromyographic guidance and lidocaine cream at each injection site. Five injection sessions were carried out in the three women.

The first patient had an 8-year history of unremitting pelvic pain, which was relieved for 9 months after her first injection session. A second injection session provided another 1.5 years of relief.

The second patient had a history of severe pelvic pain that limited her ability to walk. She had amenorrhea as a result of 5 years of treatment with leuprolide acetate and add-back therapy.

After one injection session, she had 1 year of pain relief, resumed normal menstrual cycles, and regained her ability to walk with minimal pain and normal gait, said Dr. Merideth.

And the third patient had pelvic floor spasm and bladder atony following laparoscopic surgery 1 year earlier. She was unable to self-catheterize because of the muscle spasm and therefore required a suprapubic catheter. Her first injection session decreased her pain and muscle spasm such that she was able to self-catheterize. After a second injection session 6 months later, she was able to decrease narcotic usage and return to work. The first two patients stopped narcotic usage entirely and also returned to work.

Spasm of the pelvic floor muscle is not a finding in all patients with endometriosis, and “one would anticipate this treatment would only work in patients who had spasm on exam,” said Dr. Merideth. “How it plays into their pain and the neural-immune response of the body is something we're still studying.” She said there are plans to proceed with a blinded study comparing the medication to placebo in a larger group of women.

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