Abstract

Objectives: Ultrasonography (US) has shown increased cross-sectional area of the median nerve in carpal tunnel syndrome (CTS). Knowledge of the normal distribution of the areas is a prerequisite to evaluate pathology. Presently, the distribution of cross-sectional areas of the median nerve was explored in patients with rheumatoid arthritis (RA).

Methods: The median nerves of patients with RA having no symptoms or signs of CTS were examined with bilateral US at the entrance of the carpal tunnel.

Results: A total of 154 patients with RA were included. The median nerve was divided in 11.7% of the hands. The mean (SD) cross-sectional areas of the undivided median nerves were not significantly different on either sides (8.3 (1.5) mm² on the right side and 8.3 (1.4) mm² on the left side). The areas of the examined 308 median nerves ranged from 5.0 to 12.8 mm², with the 97.5 centile being 11.1 mm². Areas >10.0 mm² were found in 10% of the patients.

Conclusions: The mean cross-sectional areas of the median nerve in patients with RA were similar to those reported in healthy controls. However, 10% of the patients had values that overlap with areas commonly reported in patients with mild idiopathic CTS.