Ultrasonographic Evaluation of the Abductor Pollicis Brevis Muscle in Patients with Carpal Tunnel Syndrome Classified According to EMG Findings

Objective: To evaluate the relationship between quantitative muscle ultrasound parameters of the abductor pollicis brevis (APB) and disease severity in carpal tunnel syndrome (CTS). Material and Methods:This cross-sectional, comparative clinical study included 76 patients.Participants were stratified into four electromyography (EMG)-based categories (EMG-normal, mild, moderate, and severe CTS).In the transverse ultrasound images of the APB, we measured cross sectional area and thickness of the muscle.Differences in muscle thickness, cross-sectional area (CSA), and pinch strength among four groups were analyzed.Results: The CSA of the APB muscle decreases with increasing disease severity.Thickness and pinch strength are significantly decreased in severe CTS.There is a significant negative correlation between the CSA of the APB muscle and the distal motor latency of the median nerve.Conclusion: Quantitative ultrasound parameters of the APB muscle are useful for evaluating disease severity in CTS.