Cross-sectional area reference values of the median nerve at the palm using ultrasound.

Abstract

The most common neuromuscular ultrasound abnormality in carpal tunnel syndrome is enlargement of the median nerve near the distal wrist crease, but sometimes the median nerve enlarges in the palm, just distal to the transverse carpal ligament. This study was conducted to devise a protocol for measuring the median nerve in the palm and to generate reference values for nerve cross-sectional area at this site. A systematic protocol was developed, 30 healthy individuals underwent ultrasound of the median nerve in the palm bilaterally, and cross-sectional area was recorded. The mean cross-sectional area of the median nerve at the palm was between 11.4 mm2 (95% confidence interval [CI] [10.4,12.4]) and 11.6 mm2 (95%CI [10.6,12.6]). The median nerve can be measured just distal to the hook of the hamate in the palm, and the mean cross-sectional area at this site is slightly larger than it is at the distal wrist crease.