Limb-Specific Features and Asymmetry of Nerve Conduction Velocity and Nerve Trunk Size in Human.

Ayaka Nobue,Yoko Kunimasa,Masaki Ishikawa,Hiroyuki Oda,Kanae Sano,Hiromu Tsuneishi

doi:10.3389/fphys.2020.609006

Abstract

This study aimed to simultaneously examine the differences of human nerve conduction velocity (NCV) and nerve cross-sectional area (nCSA) between the upper and lower limbs and between different regions of the upper and lower limbs. Thirty healthy subjects volunteered for the study. NCV and nCSA of the ulnar and tibial nerves were measured with the dominant and non-dominant arms and the supporting and reacting legs using supramaximal electric stimulation and peripheral nerve ultrasonography at three regions for ulnar and tibial nerves, respectively. Supramaximal electric stimulation was superficially applied to the ulnar and tibial nerves at each point. These action potentials were recorded from the digiti minimi and soleus muscles for the ulnar and tibial nerves, respectively. Our results clearly showed that the NCV, nCSA, and circumference of the ulnar and tibial nerves were higher and greater in the lower limbs than in the upper limbs. The greater the circumference, the greater the nCSA for both the upper and lower limbs. However, unlike the upper limbs, the supporting leg did not have higher NCV than the reacting leg despite its greater circumference. Therefore, nCSA can be related to the circumference but not necessarily function for NCV developments of the lower limbs. These various aspects between the upper and lower limbs suggest that NCV does not depend on the nCSA sizes or upper and lower limb circumference; the results indicate the existence of limb-specific NCV but not nCSA developments.

Highlights

The elucidation of the neuromuscular function of the human peripheral nervous system that enables rapid and accurate limb movements can be revealed by evaluating the morphology and functional characteristics of the peripheral nerves
The nerve cross-sectional area (nCSA) of the ulnar and tibial nerves of the participants were measured by ultrasonography [Noblus, Hitachi Aloka Medical Ltd., a high-frequency (18 MHz) linear array ultrasound transducer; image resolution: 0.08 mm] in the sitting position with the forearm flexed at 120° and in the abdominal position, respectively
Our results clearly showed that the lower limbs had higher and greater nerve conduction velocity (NCV), nCSA, and circumference than the upper limbs

Summary

Introduction

The elucidation of the neuromuscular function of the human peripheral nervous system that enables rapid and accurate limb movements can be revealed by evaluating the morphology and functional characteristics of the peripheral nerves. Hatta et al (1995) reported that the NCV and dominant forearm circumference were faster and greater in badminton and kendo players than those in the healthy control subjects. Limb-Specific Human Neuromuscular Characteristics the analysis of the peripheral nerve size in vivo is difficult and many reports are only available on human NCV. They imply that the developments of the human arm circumference and its muscle size would develop the human NCV. High resolution imaging techniques of the peripheral nerve in vivo are expected to prove the above speculation

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Conclusion