Trigger point injection with steroids and pulsed radiofrequency treatment of trigger points may relieve pain associated with abdominal myofascial pain syndrome (AMPS) effectively, according to a study published in Pain Medicine. In addition, trigger point injection with anesthetics was found to be useful in diagnosing AMPS.
In this prospective audit of chronic refractory abdominal pain management, the investigator assessed localized chronic abdominal pain in 153 adult patients who were seen by a pain physician.
The management pathway for these patients included a medical management protocol consisting of 4 steps. Step 1 was a trial of amitriptyline, pregabalin, and tramadol. Patients with localized myofascial pain were given 5% lidocaine plaster and offered transcutaneous electrical nerve stimulation plus acupuncture.
Step 2 consisted of trigger point injection with local anesthetic within 8 weeks of diagnosis. Step 3 was undertaken for patients unresponsive to step 2 treatment and consisted of trigger point injection of depot steroid plus local anesthetic. Step 4 was pulsed radiofrequency of the trigger points, which was administered to those who did not respond to step 3 treatment. After each intervention, a nurse specializing in pain management followed up with the patient by telephone.
In the final analysis, outcomes of 120 patients with AMPS who had followed this structured management pathway were audited over a 3-year period. A significant improvement was observed in 7 patients who received initial medical management. A total of 4 weekly acupuncture sessions (>4 weeks) were deemed ineffective for relieving pain for ≥4 weeks in 25 patients. Among the remaining 113 study participants for whom medical management had been unsuccessful in relieving pain, 9 refused trigger point injections and 30 patients received a local anesthetic treatment, to which all reported >50% pain relief within a 30-minute period following treatment. However, for these patients, pain had returned to baseline levels at 3-month follow-up.
Study participants in whom medical management was not effective and who had received local anesthetic (n=30) or not (n=74) received a trigger point injection with steroids. This third step of the pathway was effective in 21 patients (20%) in the short term, and an additional 33 participants (32%) were considered “durable responders,” with pain relief sustained for up to 6 months.
Some of those who did not respond (n=50; 48%) and those who had short-term response were enrolled in step 4 (n=43) in which they underwent pulsed radiofrequency treatment. This step led to durable pain relief for 26 patients (60%), with an additional 5 patients responding to treatment (12%) and 12 patients (28%) not responding to treatment.
Effective treatment of abdominal pain was associated with a high percentage of patients maintaining gainful employment (66%) and with reduced anxiety and depression (P =.005 and P =.001, respectively) at 6 months.
The open-label nonrandomized design and the small number of patients seen by a single physician represent the primary limitations of this study. In addition, the inability to blind clinicians and patients to interventions may have influenced the observed improvements.
“This work offers additional support for peripherally maintained mechanisms for viscerosomatic convergence in AMPS,” concluded the study authors.
Niraj G. Pathophysiology and management of abdominal myofascial pain syndrome (AMPS): a three-year prospective audit of a management pathway in 120 patients [published online February 9, 2018]. Pain Med. doi: 10.1093/pm/pnx343