Anterior Scalene Muscle Block for Diagnostic and Surgical Planning in Pediatric Thoracic Outlet Syndrome—Two Case Reports

Background/Objectives: Thoracic outlet syndrome (TOS) is a rare and difficult-to-diagnose condition in children, characterized by the compression of neurovascular structures in the thoracic outlet. Neurogenic TOS (nTOS) often presents with nonspecific symptoms such as paresthesia, weakness, and upper extremity discomfort. While anterior scalene muscle block (ASMB) has been used in adults as a diagnostic adjunct, its role in pediatric patients remains underreported. Methods: We present two adolescent female patients with suspected neurogenic thoracic outlet syndrome (nTOS) who were referred to the acute pain service for further evaluation. Both patients underwent ultrasound-guided ASMB. Results: Following the block, both patients experienced rapid and marked relief of symptoms. Subsequently, each underwent first rib resection with brachial plexus neurolysis. At follow-up, both patients reported a complete resolution of symptoms and a return to baseline function. Conclusions: These cases suggest that ASMB may serve as a functional diagnostic tool and short-term therapeutic test in pediatric nTOS patients. It also helps guide surgical decision-making for invasive treatment. However, as ASMB is not without risk, its role should be considered supportive rather than confirmatory. Further studies are needed to better define its utility and safety in the pediatric population.