Indications for neuromuscular ultrasound: Expert opinion and review of the literature

Highlights

• Experts routinely use ultrasound to evaluate both common and rare disorders of nerve and muscle.

• Accumulated evidence now puts diagnostic neuromuscular ultrasound on par with EMG and NCS.

• Medical centers must acquire ultrasound equipment to keep electrodiagnostic laboratories current.

Abstract

Over the last two decades, dozens of applications have emerged for ultrasonography in neuromuscular disorders. We wanted to measure its impact on practice in laboratories where the technique is in frequent use.

After identifying experts in neuromuscular ultrasound and electrodiagnosis, we assessed their use of ultrasonography for different indications and their expectations for its future evolution. We then identified the earliest papers to provide convincing evidence of the utility of ultrasound for particular indications and analyzed the relationship of their date of publication with expert usage.

We found that experts use ultrasonography often for inflammatory, hereditary, traumatic, compressive and neoplastic neuropathies, and somewhat less often for neuronopathies and myopathies. Usage significantly correlated with the timing of key publications in the field. We review these findings and the extensive evidence supporting the value of neuromuscular ultrasound. Advancement of the field of clinical neurophysiology depends on widespread translation of these findings.

Introduction

For much of the last fifty years, there has been remarkable uniformity in electrodiagnostic practice. Aside from the rare patient who might need referral to a specialized center for a single fiber EMG study, patients have been able to receive consistent diagnostic evaluations with comparable results regardless of the size of the laboratory or its geographic location. However, now a number of laboratories provide advanced ultrasound imaging in addition to standard electrophysiological assessment of nerve and muscle, a trend that appears to be accelerating, and this is creating an unprecedented gap between ultrasound enhanced and standard clinical neurophysiology practice.

Over 25,000 papers have now been published in PubMed on diagnostic ultrasound of nerve and/or muscle. It accurately establishes a diagnosis for a wide variety of neuromuscular disorders (Hobson-Webb et al., 2018, Pillen et al., 2016, Cartwright et al., 2012). Furthermore, the technique has also changed the way we think and speak. In the past it was common parlance to say that the nerves in chronic entrapment syndromes were “pinched,” but now we have all seen how they can be focally or diffusely enlarged, subject to dynamic compression or internally distorted (Tagliafico 2016). The purpose of this study was to conduct a survey of experts to see how neuromuscular ultrasound is changing electrodiagnosis, its scope of applications, and to determine to what extent ultrasound should be considered optional versus necessary in a modern clinical neurophysiology practice. It also looked to see how closely the date of publications on new indications for ultrasound correlated with actual use of the technique, and finally, it reviewed the literature, to present the evidence on the use of ultrasound for neuromuscular indications.