Ultrasound-guided Transmuscular Quadratus Lumborum Block with Depot Steroids in the Management of Abdominal Myofascial Pain Syndrome

Background: Trigger point injection is the current standard in the management of abdominal myofascial pain syndrome (AMPS). However, multiple trigger point injections can cause significant discomfort and there is a possibility of missing trigger points resulting in a reduced efficacy of trigger point treatment. Recently, abdominal wall blocks have been reported in the management of chronic abdominal wall pain. Transmuscular quadratus lumborum block (TQLB) is a novel abdominal wall block. Objective: The report describes the role of the ultrasound-guided TQLB with depot steroids in the management of AMPS. Study Design: Prospective case series. Setting: Tertiary pain medicine clinic in a University Hospital. Methods: Adult patients with AMPS under the care of a single physician were offered TQLBs with a mixture of local anaesthetic and depot methylprednisolone instead of multiple trigger point injections as a part of an on-going prospective longitudinal audit into the management of AMPS. Patients completed brief pain inventory questionnaire at baseline and at 12 weeks postprocedure. Results: Thirty patients underwent TQLB. All patients reported complete absence of pain within 15 minutes of the block and sensory testing revealed extensive hypoaesthesia extending from thoracic T6 to T12 anteriorly. Clinically significant benefit at 12 weeks was reported by 36% of patients, with 60% (18/30) of the patients preferring to receive the novel intervention instead of multiple trigger point injections. None of the patients reported post-procedural flare up. Limitations: Open label case series in a small cohort. Conclusion: The prospective series in a limited cohort suggests that TQLB with depot steroids could play a role in the management of AMPS. Key words: Abdominal myofascial pain syndrome, transmuscular quadratus lumborum block, trigger point treatment, nonspecific abdominal pain, viscerosomatic convergence