Nerve Ultrasound Protocol to Detect Dysimmune Neuropathies

Summary

This article presents a protocol for nerve ultrasound in polyneuropathies to aid the diagnosis of inflammatory neuropathies.

Abstract

Nerve ultrasound is increasingly used in the differential diagnosis of polyneuropathy as a complementary tool to nerve conduction studies. Morphological alterations of the peripheral nerves, such as increasing the cross-sectional area (CSA), have been described in various immune-mediated polyneuropathies. The most prominent morphological changes in nerve ultrasound have been described for the chronic inflammatory demyelinating polyneuropathy (CIDP)-spectrum disease. CIDP may be distinguished from hereditary and other polyneuropathies by measuring the extent and pattern of nerve swellings (CSA increase). Typical findings in demyelinating inflammatory neuropathies are multifocal nerve swellings with inhomogeneous fascicular structure, while CSA increase in demyelinating hereditary neuropathies occurs in a more generalized and homogenous manner. In other non-inflammatory axonal neuropathies, nerves can appear with normal or slight CSA increases, especially in typical entrapment sites. This article presents technical requirements for nerve ultrasound, an examination procedure using a standardized examination protocol, current reference values for the CSA, and typical sonographic pathological findings in patients with inflammatory neuropathies.

Introduction

Next to clinical examination, evaluating any large-fiber polyneuropathy includes an electrophysiological examination to characterize the motor or sensory system's involvement and differentiate axonal from demyelinating damage¹. In axonal polyneuropathy, toxic and diabetic neuropathy are the leading causes, while in demyelinating polyneuropathies, hereditary or inflammatory neuropathies such as CIDP should be considered^2,3,4. Commonly used diagnostic criteria for CIDP are the European Federation of Neurological Societies/Peripheral Nerve Society (EF....

Protocol

All examinations for this work were performed in compliance with institutional guidelines of the Ruhr-University Bochum, Germany.

1. Experimental preparations

1. Patient preparation
   1. Check the patient inclusion criteria: examine adult patients diagnosed with polyneuropathy, suspicious of inflammatory origin.
   2. Check the patient exclusion criteria: do not examine patients with open wounds or infections in the regions to be examined.
2. Instrumental checkpoints
   1. Check the integrity of the ultrasound machine and all the materials used (see Table of Materials).
   ....

Results

Each ultrasound laboratory should establish its CSA reference values by collecting data from the healthy local population, as specific ultrasound machines and examiner or population-dependent variables can lead to slightly different results in each laboratory. However, to indicate which CSA values can be considered normal, data from two leading German nerve ultrasound groups and a recent meta-analysis of all published reference values so far^13,14,

Discussion

Nerve ultrasound is a helpful additional diagnostic tool in polyneuropathies. It can give information on the possible causes of polyneuropathy depending on the extent and pattern of nerve enlargement. Moreover, CSA alterations in the longitudinal disease course of patients with CIDP were described to correlate to clinical disease course and treatment response^33,34,35,36.

Materials

Name	Company	Catalog Number	Comments
Affiniti 70	Philips GmbH	n/a	with preset for neuromuscular ultrasound
L18-5 linear array transducer	Philips GmbH	n/a
Ultrasound gel	C + V Pharma Depot GmbH	n/a