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

## TL;DR

This paper reports two cases where a muscle block helped diagnose and guide treatment for a rare condition in adolescents.

## Contribution

Demonstrates the use of anterior scalene muscle block as a diagnostic and therapeutic tool in pediatric thoracic outlet syndrome.

## Key findings

- Both patients experienced rapid symptom relief after the muscle block.
- Surgical intervention based on the block led to complete symptom resolution.
- ASMB can guide surgical decisions in pediatric neurogenic TOS.

## Abstract

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.