Exploring subclinical median nerve biomechanical changes in elderly rheumatoid arthritis patients with nerve ultrasound and shear wave elastography: a cross-sectional study

In elderly patients with rheumatoid arthritis (RA), subclinical median nerve (MN) involvement often goes undetected. This study aimed to evaluate whether combining nerve-ultrasound with shear wave elastography (SWE) could identify early MN alterations. A cross-sectional study enrolled 81 RA patients (≥ 60 years) without clinical symptoms of MN neuropathy, divided into late-onset RA (LORA) and young-onset RA (YORA), and 51 controls. Nerve ultrasound was used to measure the cross-sectional area, anteroposterior diameter, and transverse diameter of the median nerve.; SWE was used to assess the elastic index (EI) and velocity index (VI). The primary outcomes were the EI and VI. ANOVA and ROC analyses were performed. Intrarater and interrater reliability were assessed using intraclass correlation coefficients (ICCs). The three groups did not exhibit significant differences in morphology or other baseline characteristics (P > 0.05). However, significant differences in the EI and VI were observed. Individuals with YORA demonstrated a higher EI (187.43 ± 91.34 kPa) and VI (7.67 ± 1.83 m/s) than those with LORA (EI: 140.94 ± 70.58 kPa; VI: 6.60 ± 1.71 m/s) or controls (EI: 130.61 ± 61.35 kPa; VI: 6.33 ± 1.55 m/s) (P = 0.001). Furthermore, the EI and VI were correlated with the duration of RA (r = 0.481, r = 0.460; P < 0.001). The ROC analysis yielded area under the curve (AUC) values of 0.611 for the EI and 0.622 for the VI. The ICCs for intrarater and interrater reliability were ≥ 0.90 for both EI and VI. SWE can detect early differences in MN stiffness in elderly RA patients, even with normal nerve size. Combined with nerve-ultrasound, SWE provides morphological and quantitative elasticity data and provide preliminary imaging clues for early subclinical neural biomechanical changes.