What is neuromuscular ultrasound

and what can it do for you –

An introductory guide into a new diagnostic modality

Neuromuscular ultrasound is a tool, that is relatively new in the diagnostic spectrum of disorders of the peripheral nerves and muscles. It is still a niche and not applied ubiquitously, but there is a growing community of professionals aware of its usefulness. Research advances quickly, providing us with a solid base for responsible application and guidelines for diagnosing start being established.

As centers for neuromuscular ultrasound are fairly widespread on this beautiful planet, making use of the world wide web to bring us more closely together seemed to make sense. Therefore we, who are also deeply involved into the topic, decided to create this platform as a central pit stop for all of you, who are interested.

With the following text we intend to give an overview on neuromuscular ultrasound, its professional and technical requirements, indications and typical findings.

What is neuromuscular ultrasound?

The term neuromuscular ultrasound refer to the central elements of examination – nerves and muscles. 

This differs a little bit from the classical use of the term “neuromuscular” in the field of neurology, where the “neuromuscular system” is the sum of all motor units – referring to the lower motor neuron in the spine, its axon, the neuromuscular junction and all muscle fibers innervated by this motor neuron and the term “neuromuscular diseases” is used to sum up disorders of the muscles (like myopathies, myositis, disorders of the neuromuscular junction and motor neuron diseases), but separates them from disorders of the nerve like compression neuropathies, nerve trauma or polyneuropathies of any origin – which are, however, part of neuromuscular ultrasound.

So if we try to reach a definition of neuromuscular ultrasound the most appropriate might be:

Neuromuscular ultrasound deals with visualization of nerves and muscles with the goal of aiding the diagnosis of either

1. Mono- and polyneuropathies or

2. Myopathies

of different origin. When searching for neuropathies, also alterations of the muscles supplied by a specific nerve might guide you the way.

Further, visualization of nerves and muscles can be used as help for applying targeted therapy and performing optimized electromyographic studies.

Who performs neuromuscular ultrasound?

Neuromuscular ultrasound is a beautiful example of multi- and interdisciplinary work.

Various professionals apply ultrasound for different indications and will experience neuromuscular ultrasound as a natural extension of their expertise, because they are already in contact with peripheral nerve disorders.

Among the groups of potential operators are:

• MDs of different specialities – neurologists, radiologists, specialists in physical medicine and rehabilitation, specialists for internal medicine, orthopedics or plastic surgeons.
• Sonographers, most probably those colleagues who are already interested in musculoskeletal sonography and thereby nearly inevitably get involved in peripheral nerve disorders as well.
• Neurophysiology technologists, who daily deal with the complementary tool for peripheral nerve assessement: nerve conduction studies and electromyography, in order to overcome limitations of functional assessment.
• … and whoever is interested in this field.

What are the technical requirements for performing neuromuscular ultrasound?

Depending on which nerves you plan to assess, you might have to deal with some really small structures of a diameter less than 1 mm. This might make you extend to higher frequencies and therefore higher resolution than ever before. As this is quite special, we assembled an own blog post with example images and videos on this topic which you can view here.

Assessment of muscles is less a technical challenge. It can be performed with lower frequency probes you will usually already have around. In this case you are not into the tiny detail, but rather in the big picture. The challenges about muscle ultrasound are two: 1. Finding the right muscle when you start out and 2. Securely adjusting your eye to the normal picture and then recognize the pathology. 

What are the professional requirements for performing neuromuscular ultrasound?

Neuromuscular ultrasound needs you to bring a minimum interest in understanding of clinical presentation and clinical examination of patients with neuropathies and myopathies. Why? Because in neuropathies in 98% of cases you will see one morphologic alteration: a thickening of the nerve. To see if it fits a clinically suspected diagnosis, you need to be aware the major features. This is why our online courses strongly build on getting the whole picture rather than only seeing the nerve.

If you start with a professional background that does not imply training in electrodiagnostic testing on a regular basis, you should be willing to invest maybe an hour of your lifetime into understanding the principles of electrodiagnostic testing. This is necessary, because electrodiagnostic testing is THE complementary tool to neuromuscular ultrasound.

The fundamental principle in diagnosing peripheral nerve disorders is the triad of

clinical examination – electrodiagnostics – imaging

Clincial examination is the gold standard. It defines the deficits and allows you to establish a working diagnosis. Upon your findings you set up a plan for the additional examinations you need to objectify your suspicion. The major two ways are imaging and electrodiagnostics.

Electrodiagnostics will give you the functional status of the nerve. It tells you if it works at all, if yes, how much of it works and which of the two transmitting structures – the axon or the myelin sheath – is primarily impaired. These are answers that ultrasound cannot give.

Ultrasound, on the other hand, tells you about the morphological state of a nerve. It can tell you exactly the site at which it is impaired, the length of the impaired section and if the impairment is situated within the nerve itself or is caused by something e.g. compressing the nerve from outside. These are answers that electrodiagnostics cannot give.

Therefore complementary use of both methods is warranted.

What are typical findings in neuromuscular ultrasound?

The by far most frequent morphologic finding in ultrasound of peripheral nerves is a circumscribed enlargement of a nerve – which can have a wide variety of reasons. Quantification of the swelling is usually carried out by measuring the cross-sectional area (CSA), expressed in square millimeters.

In ultrasound of muscles the situation is a little more complex. Pathologic findings include changes of thickness, echogenicity and architecture of the muscle as well as documentation of involuntary movements as they appear e.g. in motor neuron diseases.

In which disease entities can neuromuscular

ultrasound be of good help?

Let´s start with the nerves.

The answer is: if you consider everything that can happen to a peripheral nerve, ultrasound can assist you in nearly every disorder:

1. Hereditary neuropathy
2. Nerve trauma
3. Entrapment neuropathy (well, which is a nerve trauma)
4. Infection, especially leprosy
5. Auto-immune disease
6. Nerve tumors

From the current perspective, the only entity in which ultrasound cannot help you or give you additional information is metabolically induced axonal polyneuropathy, which includes diabetic neuropathy.

What if I want to start?

Then you can use our materials and courses.

For a first look we offer our nerve guide. Everything starts with the correct localization of the nerve.  You chose the optimal point for picking the nerve up, then follow it distally and proximally along its course. Our nerve guide demonstrates where to find a specific nerve, showing probe orientation and corresponding ultrasound image. You can download it here.

For moving on to a first structured training, that provides you with a comprehensive knowledge on how to diagnose with ultrasound in conjunction with clinical findings and electrodiagnostics, check out our course on the idiopathic carpal tunnel syndrome here.

And if you are finally convinced about the modality and our way of training, then our Basic Course is available to turn you into an expert for scanning and diagnosing along the most frequently requested nerves. For more details please have a look here.