Normative Cross-Sectional Area of the Brachial Plexus and Subclavian Artery Using Ultrasonography

Abstract

Objective Ultrasonography has been used to measure the cross-sectional area (CSA) of peripheral nerves, but the CSA of the brachial plexus has not previously been reported. The purpose of this study was to establish a reference range of values for the CSA of the brachial plexus, subclavian artery, and peak systolic velocity (PSV) of the subclavian artery in healthy subjects using ultrasonography. Methods Thirty-two asymptomatic subjects (19 men, 13 women) from a chiropractic college with an average age of 29.5 ± 9.6 participated in the study. The brachial plexus and subclavian artery CSA were measured at 3 locations: interscalene, first rib, and infraclavicular. The PSV of the subclavian artery was measured in both supraclavicular and infraclavicular locations. Each subject was imaged bilaterally. Means and 95% confidence intervals were calculated. Interexaminer reliability was evaluated between 2 examiners on 15 randomly selected subjects. Results The average CSA for the brachial plexus at the interscalene space, first rib, and infraclavicular location was 0.75 ± 0.05, 0.96 ± 0.07, and 0.98 ± 0.07 cm 2, respectively. The average CSA for the subclavian artery at the same locations was 0.35 ± 0.03, 0.38 ± 0.03, 0.35 ± 0.03 cm 2, respectively. The average subclavian artery PSV in supraclavicular and infraclavicular locations was 98 ± 8 and 93 ± 7 cm/s, respectively. The overall interexaminer reliability was poor at 0.39 (0.20-0.55). Conclusions This is the first study to obtain normative CSA measurements of the brachial plexus and subclavian artery in multiple locations of the thoracic outlet as well as interexaminer reliability data. These data may be beneficial in future studies designed to assess the brachial plexus and subclavian artery in patients with thoracic outlet syndrome.