Ultrasound Evaluation of Anatomic Variations of the Median Nerve and Carpal Tunnel — WRNMMC Research and Innovation Month 2022

Super E, Smith M, Persinger J, Hager N, Smith J, Miller M, Yuan X

Abstract Submitted to WRNMMC Research and Innovation Month 2022

Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment. Interventional procedures for CTS include carpal tunnel (CT) injections and CT release (CTR). Variant anatomy increases the risk of iatrogenic injury and complications, impairing recovery and leading to post-procedural functional deficits. The objective of this study was to evaluate anatomic variations associated with CTS or at risk of injury during procedures using high-frequency ultrasound (HFUS). In this cross-sectional, observational study of 100 eligible patients (age: 44.4 ± 13.0 years, 37.0% female) referred for upper extremity (UE) electrodiagnostic studies (EDX), the MN was systematically evaluated using high-frequency ultrasound (HFUS) from the elbow to the CT outlet. The presence/absence of Martin-Gruber anastomosis (MGA), palmaris longus, and lumbrical intrusion with dynamic finger flexion at the CT inlet were documented, along with the course of the palmar cutaneous branch of the MN (PCBMN) and thenar motor branch (TMB. The cross-sectional area (CSA) of the MN at the level of the CT inlet and the transverse safe zone (TSZ) for CTR were measured. Statistical analyses were conducted using GraphPad Prism. All data are presented as mean ± standard deviation or percentage (%).