Chronic pelvic pain affects millions of women. Per the American College of Obstetrics and Gynecology, chronic pelvic pain is any pelvic pain that lasts for more than six months and occurs in the pelvis or lower abdomen. Its etiology can be from organs, muscles, nerves, bones, and vessels within the pelvis. Pelvic floor muscles with increased pelvic floor muscle tone are excellent targets in the approach to treating pelvic pain. The European Association of Urology's guidelines on chronic pelvic pain start with conservative management prior to pain management and more invasive measures. A detailed history of chronic pain is undertaken to identify the possible origin. This includes the patient’s obstetric, gynecologic, genitourinary, gastrointestinal, and skeletal history. During the pelvic exam, the pubococcygeus, iliococcygeus, ischiococcygeus, puborectalis, and obturator muscles are assessed for tone, strength, and discomfort. We sought to evaluate the effectiveness of using onabotulinum toxin A for patients with disorders of increased tone due to pelvic floor tension myalgia and pelvic floor myofascial pain syndrome as well as pelvic floor pain due to pelvic floor myalgia. These are patient who have not had success with pelvic floor targeted physical therapy training.

During the procedure, the main instruments used include a Chalgren 75 mm injectable monopolar needle electrode, EMG return electrode, LifeTech MiniStim peripheral nerve stimulator, split Graves speculum, and 100 units of onabotulinum toxin. The 100U of onabotulinum toxin is reconstituted with 2cc of preservative free injectable saline, making it more concentrated than standard mixing based on the small target for delivery.

The patient is counseled that an awake exam will be performed in the operating room. The surgeon performs a pelvic exam assessing which muscles exhibit increased tone and elicit tenderness, thereby mapping which muscles will benefit from injection. Often this exam is informed by input from the pelvic floor physical therapist preoperatively. The patient is then sedated. Then the EMG electrode is placed at the 2 or 10 o’clock position on the perineum just anterior to the anus. It should be noted that more stimulation will be required to transmit on the contralateral side. Using the peripheral nerve stimulator EMG device, with the dial turned to an intensity of about 4 to start, a double burst is administered to confirm appropriate localization of pelvic floor muscles. Contraction of the pelvic floor muscle without activation of the leg will be appreciated when the injection needle is optimally placed. The appropriate puborectalis, pubococcygeus, iliococcygeus, ischiococcygeus, and obturator muscles are targeted based on the physical exam. Each muscle receives two injections about one to two centimeters apart. The 100 units of onabotulinum toxin is equally divided among the targets.

Using onabotulinum toxin A at the pelvic floor muscles can relieve disorders of increased pelvic floor tone and pelvic floor pain for about 6 months. This treatment is best applied to patients who have hit a plateau in pelvic floor physical therapy, have been unable to tolerate physical therapy, or have continued promotors of high tone pelvic floor dysfunction. Formal analysis of data has not been performed for this video technique demonstration. This is currently an off label chemodenervation treatment. However, there is currently some data in the literature on this.

Clinical observation shows that in patients with refractory high tone pelvic floor muscle dysfunction, onabotulinum toxin can be used to augment relaxation. Pelvic floor physical therapy can often be resumed after onabotulinum toxin injection and often can augment results. Patients should be counseled that symptoms can worsen for one to three weeks while the chemodenervation is taking hold.

Fall M, Baranowski AP, Fowler CJ, et al. EAU Guidelines on Chronic Pelvic Pain. http://www.uroweb.org/guidelines/online-guidelines/
Gray's Atlas of Anatomy. The Anatomical Basis of Clinical Practice. 41st Edition. Standring, Susan MBE, PhD, DSc, FKC, Hon FRCS.  Elsevier Limited. Standring, Susan, MBE, PhD, DSc, FKC, Hon FAS, Hon FRCS. Published January 1, 2016. Pages 1221-1236.e1.

Continence 2S2 (2022) 100401
DOI: 10.1016/j.cont.2022.100401