D136. Role of Anterior Scalene Muscle Block in Predicting Outcomes in Rib-sparing Vs. First Rib Resection Techniques For Thoracic Outlet Syndrome

PURPOSE: Thoracic outlet syndrome (TOS) is a potentially debilitating condition that can present with upper extremity paresthesia, pain, and weakness. Temporary symptomatic improvement after anterior scalene muscle block (ASMB) may be positively correlated with improvement after thoracic outlet decompression (TOD). We assessed the role of pre-operative ASMB and its predictive value for TOD outcomes. METHODS: Single-institution retrospective chart review was performed between January 2017 and September 2024 to identify patients with isolated/combined TOS treated with surgical decompression. Data extracted included demographic information, preoperative symptoms, surgical technique and complications, and functional outcomes. Improvement after TOD was defined as improved sensory/motor function and/or decreased pain. Statistical analysis was performed using Fisher Exact and Welch’s two-tailed t-test. RESULTS: 105 patients (54.28% female) with a median age of 39 years, met inclusion criteria. Eighteen underwent decompression with rib resection versus 87 who underwent a rib-sparing technique. The two groups were demographically similar. Of the patients who improved after pre-operative ASMB and had postoperative follow up data (n=27), 81.81% improved after TOD. Of those, the majority (61.11%) received rib-sparing TOD rather than with rib resection (38.88%). CONCLUSION: TOS is a complex disorder without gold standard diagnostic tools or treatments. ASMB has been hypothesized to predict successful TOD. In this study, patients who underwent ASMB with symptomatic improvement had a high likelihood of improvement after TOD. A greater proportion of those who benefited from surgery were treated with a rib-sparing technique. Future prospective studies are needed to establish a standard of care for this challenging disorder.