Misdiagnosing Abdominal Myofascial Pain Syndrome as Anterior Cutaneous Nerve Entrapment Syndrome: Are we Failing Patients with Nonspecific Abdominal Pain?

Background: Chronic abdominal wall pain (CAWP) is often undiagnosed and results in significant health care use as well as patient suffering. There are two main types: abdominal myofascial pain syndrome (AMPS) and anterior cutaneous nerve entrapment syndrome (ACNES). Although the 2 conditions share clinical similarities, they have subtly distinct unique features. Objectives: To highlight the current practice, elucidate the characteristics of the 2 types of CAWP, and direct the spotlight on abdominal myofascial pain. Study Design: Prospective case series. Setting: Tertiary pain medicine clinic in a university hospital. Methods: As a part of a prospective audit of management of chronic abdominal pain, patients completed brief pain inventory-short form questionnaires at baseline and at 3 months posttrigger point treatment. Results: All 3 patients were misdiagnosed with ACNES. Patient 1 was attending the emergency department once every 5 days prior to being correctly diagnosed with AMPS. Following trigger point treatment, there was a significant reduction in emergency department attendance. Patient 2, with a 10-year history of lower abdominal pain that resulted in severe disability, was able to mobilize following trigger point treatment. Patient 3, with a high opioid use (360 mg per day), was able to discontinue opioids following ultrasound-guided trigger point injection with depot steroids. Limitations: Open label case series in a small cohort. Conclusions: AMPS is as common as the various visceral inflammatory diseases. Lack of awareness, ignoring its existence, and misdiagnosing it may not benefit patients with chronic abdominal pain. Key words: Chronic abdominal wall pain, abdominal myofascial pain syndrome, anterior cutaneous nerve entrapment syndrome, viscerosomatic convergence