After periodic assessment by questionnaire and examination through 6 months after injection, no differences were found in the pain score or resting vaginal pressure between the group of women who received botulinum toxin A and the group who received placebo. However, each group experienced a significant reduction in pain and vaginal pressure, compared with baseline. And both groups reported improved quality of life, compared with baseline. Neither group reported voiding dysfunction.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
These two studies support the use of trigger-point injection into pelvic floor muscles to reduce pelvic myofascial pain. The findings of Abbott and colleagues, in particular, suggest that the substance that is injected may not be as important as the actual needling of the muscle. Larger studies and comparisons between placebo, botulinum toxin A, and anesthetic solutions are needed to elucidate the therapeutic benefit of these particular medications.
Neuromodulation shows promise as treatment for pelvic myofascial pain
van Balken MR, Vandoninck V, Messelink, BJ, et al. Percutaneous tibial nerve stimulation as neuromodulative treatment of chronic pelvic pain. Eur Urol. 2003;43(2):158–163.
Zabihi N, Mourtzinos A, Maher MG, Raz S, Rodriguez LV. Short-term results of bilateral S2-S4 sacral neuromodulation for the treatment of refractory interstitial cystitis, painful bladder syndrome, and chronic pelvic pain. Int Urogynecol J Pelvic Floor Dysfunct. 2008;19(4):553–557.
Neuromodulation is the science of using electrical impulses to alter neuronal activities. The exact mechanisms of action are unclear, but the technology has been utilized to control symptoms of overactive bladder and urinary retention caused by poor relaxation of the urethral and pelvic floor muscles. While studying the effects of sacral nerve root neuromodulation on the bladder, investigators noted improvements in other symptoms, such as pelvic pain.
Neuromodulation of the sacral nerve roots may be achieved by direct conduction of electrical impulses from a lead implanted in the sacrum (sacral neuromodulation) or by the retrograde conduction of these impulses through the posterior tibial nerve (percutaneous tibial nerve stimulation, or PTNS) (FIGURE 2). The tibial nerve arises from sacral nerves L5 to S3 and is one of the larger branches of the sciatic nerve.
FIGURE 2 InterStim therapy
Stimulation of the sacral nerve has been used successfully to manage overactive bladder and urinary retention and may prove useful in the treatment of pelvic myofascial pain.
Van Balken et al: Details of the study
In this prospective observational study, 33 patients (both male and female) who had chronic pelvic pain by history and examination were treated with weekly, 30-minute outpatient sessions of PTNS for 12 weeks. Participants were asked to provide baseline pain scores and keep a diary of their pain. Quality-of-life questionnaires were also administered at baseline and at 12 weeks.
Investigators considered both subjective and objective success in their outcomes. If a patient elected to continue therapy, he or she was classified as a subjective success. Objective success required a decrease of at least 50% in the pain score. At the end of 12 weeks, although 33 patients (42%) wanted to continue therapy, only seven (21%) met the definition for objective success. Of those seven, six elected to continue therapy.
This study sheds light on a treatment modality that has not been studied adequately for the indication of pelvic pain but that may be promising in patients who have levator myalgia. Limitations of this study include the lack of a placebo arm, short-term outcome, and lack of localization of pain. Furthermore, although PTNS has FDA approval for treatment of urinary urgency, frequency, and urge incontinence, it is not approved for the treatment of pelvic pain. These preliminary findings demonstrate potential but, as with any new indication, long-term comparative studies are needed.
Zabihi et al: Details of the study
Patients in this retrospective study had a diagnosis of interstitial cystitis or chronic pelvic pain. Pelvic myofascial pain and trigger points were not required for eligibility. Thirty patients (21 women and nine men) had temporary placement of a lead containing four small electrodes along the S2 to S4 sacral nerve roots on both sides of the sacrum. They were then followed for a trial period of 2 to 4 weeks. To qualify for the final stage of the study, in which the leads were connected internally to a generator implanted in the buttocks, patients had to report improvement of at least 50% in their symptoms. If their improvement did not meet that threshold, the leads were removed.
Twenty-three patients (77%) met the criteria for permanent implantation. Of these patients, 42% reported improvement of more than 50% at 6 postoperative months. Quality-of-life scores also improved significantly.