High-frequency Ultrasonography of the Digital and Palmar Nerve Branches of the Hand in Peripheral Nerve Diseases

Summary

The present protocol describes high-frequency neuromuscular ultrasonography of the digital and palmar branches of the median and ulnar nerve, which can aid in localizing peripheral nerve diseases and be adapted to evaluate digital nerve injuries.

Abstract

Peripheral nerve ultrasound is a well-established imaging technique to evaluate certain peripheral nerve pathologies. However, there is a poor correlation between ultrasound abnormalities of peripheral nerves and electrodiagnostic or clinical evidence of axonal loss. This is a significant limitation of peripheral nerve ultrasound, as many peripheral nerve diseases encountered in clinical settings are related to axonal loss. Furthermore, clinical and electrodiagnostic evidence of axonal loss directly correlates with disability in all peripheral nerve diseases. However, due to the floor effects often encountered in electrodiagnostic studies, these correlations, as well as definitive diagnoses, are often challenging. Thus, imaging techniques that correlate with axonal loss are essential for expanding the utility of peripheral nerve ultrasound as a potential biomarker for peripheral nerve diseases. With new technological advancements and the ever-increasing imaging capabilities of high-frequency ultrasound, the palmar and digital nerve branches of the hand can be imaged with exceptionally high resolution even using point-of-care ultrasound devices. Their superficial and distal-most anatomic locations are ideal for evaluating polyneuropathies, as these branches degenerate earliest during axonal loss. However, no studies have systematically evaluated these nerve branches to determine if they can be reproducibly measured with ultrasound. The current protocol was adapted for the systematic assessment of cross-sectional areas of the median and ulnar nerves in the palmar surface and digits of the hand. This protocol provides reference data for a subset of nerves that demonstrate high intraclass correlation coefficients between three separate ultrasonographers. Finally, as a proof of concept and to demonstrate the clinical applications of this protocol, representative data from individuals with genetically confirmed inherited polyneuropathies are compared with established normative data to examine cross-sectional area differences.

Introduction

The expansion of clinical ultrasound to evaluate peripheral nerves and muscles has substantially improved the ability to diagnose neuromuscular disorders¹. Over the past 2 decades, ultrasound has emerged as a tool to directly image anatomical changes in the neuromuscular system, which correlate with pathological processes. Ultrasound is most commonly combined with clinical history and examination to provide further detail or support electrodiagnostic studies, which are considered a gold standard equivalent for diagnosing peripheral nerve disease². In some cases of focal neuropathies such as carpal tunnel syndrome, ultras

Protocol

All experiments in this study were performed in compliance with the Wayne State University and Detroit Medical Center Institutional Review Boards (IRB) under an approved protocol for the natural history of individuals with peripheral neuropathies. Informed consent was obtained from all human participants.

1. Instrumental setup

1. Enter the patient's name or other identifiers as needed to organize the captured images.
2. Sanitize the ultrasound probe (see Table of Materials) and apply ample ultrasound gel to the head of the transducer before imaging.
3. Set the capture frequency to

Results

For the normative data, 20 individuals were selected with normal electrophysiology results, no neurological complaints, past medical history of or current diabetes mellitus, thyroid dysfunction, vitamin abnormalities, metabolic syndrome, carpal or cubital tunnel syndrome, exposure to chemotherapeutics, or severe hand trauma, and who had not been pregnant within the last 1 year (Table 1). Given the small subset, we did not stratify our data by age, gender, weight, or height, all of which are known to affe...

Discussion

The present protocol describes high-frequency ultrasound of the hand's digital and palmar nerve branches. This study was designed to test the hypothesis that cross-sectional area enlargement in distal nerve branches correlates with axonal loss. Extensive multicenter natural history studies of individuals with different subsets of axonal diseases will be needed to resolve this hypothesis. In addition to its potential research benefits, this protocol can also be applied clinically to localize peripheral nerve complaint...

Materials

Name	Company	Catalog Number	Comments
10-22mHz Transducer	General Electric Health Care	H48062AB	Small foot print transducer
ImageJ	NIH	N/A	https://imagej.nih.gov/ij/
Logiq eR8 Ultrasound Beam Former	General Electric Health Care	H48522AS	This is the beamformer and image processor which includes Power Doppler Imaging
Ultrasound Gel	Parker Labratories	44873	Standard ultrasonoic gel, non sterile