Very high-resolution ultrasound of the distal median nerve

Objective: A very high-resolution (70 MHz) ultrasound device (VHRUS) has recently been approved for use in humans. The aim of this study was to use VHRUS to collect data on healthy subjects to propose some reference values for the digital branches of the median nerves of the hand. Methods: A VHRUS with 70 MHz linear array transducer was used to measure the cross sectional area of the median nerve at the wrist (CSA(w)) and digital branches (CSA(f)), largest and smallest fascicles, the fascicles number (N-fasc), the fascicle density (FD), the flattening ratio (FR) and CSA(w)/CSA(f). Results: Data from 20 healthy subjects were obtained for both hands. The median nerve at the wrist and digital branches were properly identified without anatomical alterations. No differences were found between the right and the left hand. In the dominant hand, CSA(w) was 9.35 mm(2) (4.57-12.35) and N-fasc was 24 (18-38). FD and FR were respectively 2.94 (2.47-4.91) and 2.74 (1.70-4.90). Conclusion: VHRUS technology can visualize the median nerves at the wrist, their internal structure and their small branches at the fingers, providing both a qualitative and quantitative assessment. Results from this study provide preliminary reference values in a young healthy sample. Significance: Most conventional ultrasound devices are not able to properly visualize the distal branches of the median nerve. In contrast, VHRUS allows to detect and measure smaller structures of the nerve, assisting in clinical practice. (C) 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.