High‐resolution ultrasound demonstrates in vivo effects of wrist movement on the median nerve along the forearm

Abstract

Introduction/Aims High‐resolution ultrasound (HRUS) is the imaging method of choice to visualize peripheral nerve size, structure, and biomechanical performance. The purpose of this study was to show and quantify the effects of active and passive wrist alignment on median nerve (MN) cross‐sectional area (CSA) along the forearm in a healthy population. Methods Sixteen healthy volunteers underwent HRUS of their dominant forearm (n = 16, 10 males, 6 females, 18–55 y of age). Median nerveʼs CSA was assessed at four defined areas on the forearm in relation to active and passive wrist alignment. Results Changes in wrist alignment were significantly associated with MN CSA (P < .001), regardless if the wrist was moved actively or passively. MN CSA was lowest during passive extension of the wrist joint and highest during passive flexion of the wrist joint (range: 4.5–23.2 mm2). Discussion The elasticity of nerve tissue, the loose connective tissue between the fascicles, and the paraneurium allow peripheral nerves to adapt to longitudinal strain. HRUS enables the demonstration of significant median nerve CSA changes along the forearm during active and passive wrist movement in healthy volunteers.

Median nerve versus flexor tendons: visualization of median nerve level changes in the proximal carpal tunnel during wrist movement with dynamic high-resolution ultrasound

“…Most of the young healthy volunteers showed MN level changes in both hands during the maximum wrist flexion. The finding aligns with previous research suggesting that the presence of loose connective tissue surrounding the MN in the carpal tunnel of healthy individuals leads to greater dorso-palmar movement ability, especially during wrist flexion (9) than in patients with CTS. During the translocation in between and underneath the flexor tendons, the MN shows highly flexible adaptation (deformation) in healthy individuals, as depicted exemplarily in Fig.…”