Prognostic value of scalene muscle block for surgical outcomes in neurogenic thoracic outlet syndrome

Objective Neurogenic thoracic outlet syndrome (NTOS) remains a diagnostic challenge, with surgical outcomes often difficult to predict. The reporting standards of the North American Society of Vascular Surgery recommend a scalene muscle block (SMB) as part of the diagnostic process for NTOS. This study assessed the predictive value of thoracic outlet decompression (TOD) surgery using a SMB of which the outcome is measured using a standardized Elevated Arm Stress Test (sEAST) for patients with suspected NTOS. Methods This study is a single-center, retrospective analysis of a prospectively maintained cohort. Patients with suspected NTOS between August 2016 and December 2024 were included if they underwent a SMB and received TOD surgery. Ultrasound-guided SMB with bupivacaine was performed, and outcomes were assessed using a pre- and post-SMB sEAST measurement, of which an improvement of ≥50% was defined as positive. Surgical success was defined using Derkash scores at 3 and 12 months postoperatively, complemented by TOS Disability Scale, Cervical Brachial Symptom Questionnaire (CBSQ), and Disability of the Arm, Shoulder, and Hand (DASH) scores at 3 and 6 months, and annually up to 5 years postoperatively. Results A total of 764 NTOS patients met the diagnostic criteria, of whom 465 were surgically treated and included. A positive SMB response was reported in 315 patients (67.7%). A positive SMB had a 67.8% (CI 62.2-73.0%) sensitivity for good outcome after surgery, specificity of 32.3% (CI 25.2-40.0%), positive predictive value of 64.8% (CI 60.2-67.7%), negative predictive value of 35.3% (CI 29.3-41.9%), and accuracy of 55.3% (CI 50.6-59.9%). No statistically significant differences were observed between the positive and negative SMB outcome group regarding TOS Disability Scale, DASH, and CBSQ scores at all postoperative time points. Conclusions The prognostic value of the SMB in predicting short- and long-term surgical success is limited in patients with a high suspicion for NTOS.