Chronic pelvic pain is described as pain in the pelvic area lasting for 3-6 months or longer. It has been estimated to be present in about 10% of the general population; it is present in between 5.7% and 26.6% of women and 2% to 16% of men [1,2]. Pelvic floor tension myalgia (PFTM) is a well-established condition of pelvic pain associated with increased pelvic floor muscle tone [3]. PFTM can be associated with a range of symptoms in addition to pain directly associated with the affected muscles: bladder and bowel symptoms as well as sexual dysfunction. Conservative management involving physical intervention such as pelvic floor physical therapy, stretching, and biofeedback are first-line approaches to managing this condition. However, when these are unsuccessful or not tolerated for physical or emotional reasons, Botulinum toxin A injected into the pelvic floor has shown significant improvement for patients in our subspecialty clinical practice. There are few publications describing the outcomes of Botulinum toxin A to the pelvic floor for chronic pelvic pain. We investigate patient-reported outcomes of electrical-stimulation guided Botulinum toxin A injection to the puborectalis, pubococcygeus, ileococcygeus, coccygeus, and more rarely the obturator muscles for patients with chronic pelvic pain secondary to PFTM.

We included female patients with PFTM refractory to pelvic floor physical therapy who subsequently received Botulinum toxin A to pelvic floor muscles with electrical stimulation guidance from January 1st, 2022, through March 1st, 2023. Patient-reported outcome questionnaires were mailed to patients with a return envelope. The Global Response Assessment was the primary outcome. Secondary outcomes included Visual Analogue Scales (VAS) and a structured symptom checklist. Descriptive analysis was employed for data assessment given the population size (Tables 1 and 2). Pelvic floor tension myalgia was determined on exam according to the International Continence Society report on the terminology of pelvic floor muscle assessment. 

Procedure: 
1) Before the participant was under monitored anesthesia care, the surgeon performed a repeat pelvic exam assessing which muscles exhibited increased tone and elicited tenderness to allow for targeted treatment of the appropriate muscle.  
2) IV antibiotics were administered and the vagina prepped with betadine. 
3) 100 units of Botulinum toxin A were mixed in 2 cc of 0.25% Marcaine or saline.  
4) For each injection, the target muscle was stimulated using the peripheral nerve stimulator (standard equipment anesthesiology uses to assess for muscle twitch in the operating room). An Ambu Neuroline surface EMG electrode was placed on the participant's perineum at the 10'o-clock position just anterior to the anus. A 75 mm Chalgren injectable monopolar needle electrode was connected to the nerve stimulator and was used for injection after twitching the muscle under palpation, with a starting setting of 4. Contraction of the intended pelvic floor muscle without activation of the leg was accomplished prior to each injection, or the needle was repositioned.  
5) Each muscle group received 1-2 injections of approximately 1/8 cc (10-12.5 U of Botox), about 1-2 cm apart, with the 100 units of Botulinum toxin A equally divided among the targets.

16 patients met the study criteria and 15/16 (94%) returned the questionnaire. The non-responder was classified as a failure with worsening symptoms based on the clinic visit. 6 patients previously carried a diagnosis of interstitial cystitis. Of these 6 patients, 3 were reclassified as PFTM only, and 3 as PFTM in addition. 13 patients (81%) reported improvement in pelvic symptoms, 1 neutral, and 2 with worsening symptoms. Of those improved, 7 were “markedly improved”, 4 “moderately improved”, and 2 “slightly improved” on the GRA with an average VAS of 8.6. Patients with improved symptoms most frequently reported improvement in pelvic pressure/pain (92%) as well as incomplete bladder emptying (77%). Flaring of symptoms (increased pelvic pain, pelvic cramping, pain with urination, urethral burning, dyspareunia) occurred in 7 patients (44%) for an average duration of 7.8 days. 14 patients (88%) reported interest in repeating the procedure.

Electrical stimulation-guided Botulinum toxin A to the pelvic floor muscles provided significant relief of pelvic pain in a majority of patients with PFTM. Flaring of symptoms was a common occurrence amongst patients, but largely did not deter their interest in future treatments. The importance of electrical stimulation for efficacy and safety has not been investigated, but it should be noted that repositioning of the injection needle was required frequently intraoperatively due to either lack of response of the target muscle or unwanted recruitment of lower extremity muscles.

Electrical stimulation-guided Botulinum toxin A injection of the pelvic floor muscles is an excellent treatment for refractory pelvic pain associated with pelvic floor tension myalgia. Patient-reported outcomes demonstrate significant improvement with low risk. Patients should be counseled that symptom flares are common and can be avoided by repeating treatment before the prior Botulinum Toxin has fully worn off.

Royal College of Obstetricians and Gynaecologists. Chronic Pelvic Pain, Initial Management (Green-top 41). Royal College of Obstetricians and Gynaecologists (2012). www.rcog.org.uk/globalassets/documents/guidelines/gtg_41.pdf.
A, Ahangari. 2014. "Prevalence of chronic pelvic pain among women: an updated review." Pain Physician 141-7.
Frawley et al: An International Continence Society (ICS) report on the terminology for pelvic floor muscle assessment. Neurourology and Urodynamics. 2021;40:1217–1260.  DOI: 10.1002/nau.24658

Continence 7S1 (2023) 100815
DOI: 10.1016/j.cont.2023.100815