Neuralgic amyotrophy

Mark A Ferrante MD (

Dr. Ferrante of the University of Tennessee Health Science Center has no relevant financial relationships to disclose.

)
Francesc Graus MD PhD, editor. (Dr. Graus of the University of Barcelona has no relevant financial relationships to disclose.)
Originally released May 14, 1996; last updated June 2, 2020; expires June 2, 2023

This article includes discussion of neuralgic amyotrophy, brachial neuritis, acute brachial neuropathy, acute brachial plexitis, acute brachial radiculitis, acute scapulohumeral paralysis, acute shoulder neuritis, brachial plexus neuropathy, cryptogenic brachial neuropathy, inflammatory brachial plexus neuropathy, localized neuritis of shoulder girdle, long thoracic neuropathy, multiple neuritis of shoulder girdle, paralytic brachial neuritis, Parsonage-Turner syndrome, serogenic neuropathy, serratus magnus palsy, and vaccinogenic neuropathy. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.

Overview

This article reviews neuralgic amyotrophy, a single disorder that was previously considered to be a large number of separate entities. Thus, it was previously referred to by a myriad of other terms, including the eponymous term, Parsonage-Turner syndrome. Except for neuralgic amyotrophy, which conveys the 2 quintessential clinical features of this disorder, and Parsonage-Turner syndrome, which does not convey any misleading information, the other terms are best avoided. These undesirable terms are descriptive and were coined based on 1 or more of its clinical features, such as the involved muscle (serratus magnus palsy), an antecedent event (eg, vaccinogenic neuropathy), a presumed localization (eg, acute brachial plexitis), or a presumed pathology (eg, inflammatory brachial plexus neuropathy), all of which are either inaccurate or unproven.

Because it conveys the 2 most important clinical features, this article utilizes the term neuralgic amyotrophy, which was originally introduced by Parsonage and Turner.

Unfortunately, even now, neuralgic amyotrophy is a relatively unknown entity to many healthcare providers, including many surgeons and anesthesiologists. For this reason, the recognition of this disorder by the neuromuscular medicine provider serves 2 important roles in addition to disease recognition: (1) it serves to prevent the mistaken consideration that the clinical features are due to the associated medical or surgical procedure (when this is the antecedent event) and (2) it serves to prevent unnecessary diagnostic testing and unhelpful therapeutic interventions (eg, surgery) from being performed.

Neuralgic amyotrophy is a disorder of the peripheral nervous system. Its 2 quintessential features – as indicated by the term neuralgic amyotrophy – are severe pain and significant muscle wasting. Neuralgic amyotrophy affects the forequarter region of the body (ie, the cranial, shoulder, upper extremity, and ipsilateral chest wall). In the majority of cases, a precipitating antecedent event (also referred to as a trigger) can be identified.

Because the phenotypic presentation of neuralgic amyotrophy is extremely variable, neuralgic amyotrophy was not initially recognized as a single entity. As a result, each of its individual presentations was considered to be a separate disorder and received a separate name, resulting in a large number of recognized medical diseases that were in fact a single entity. Eventually, a unifying clinical triad was identified – an antecedent event (trigger), the sudden onset of severe forequarter region pain, and severe weakness and wasting of forequarter muscles – resulting in the recognition that all of these disorders represented phenotypic variations of a single syndrome.

Even the variations of neuralgic amyotrophy reported in the literature (ie, the classic versus non-classic forms), simply reflect the nervous system element within the forequarter region involved (eg, cranial nerve, root, plexus, or nerve). Neuralgic amyotrophy may involve a single focus (most commonly a single nerve) or multiple foci (most commonly multiple nerves).

Although the majority of the lesions associated with neuralgic amyotrophy have been traditionally localized to the brachial plexus, many investigators have speculated that, at least on some occasions, the lesions must have an extraplexal localization. Subsequently, in a large review of neuralgic amyotrophy patients, it was recognized that the overwhelming majority of the lesions associated with neuralgic amyotrophy are extraplexal (Ferrante and Wilbourn 2017). This extraplexal distribution is due to the motor axon predilection of this disorder (discussed below).

This discussion reviews the demographic, genetic, and clinical features of neuralgic amyotrophy, as well as its differential diagnostic considerations, workup, and treatment. The most important step is the recognition of neuralgic amyotrophy so that unnecessary diagnostic testing and inappropriate interventions are avoided.

Key points

 

• Neuralgic amyotrophy is characterized by severe and sudden-onset forequarter region pain and forequarter muscle weakness and wasting.

 

• Although most neuralgic amyotrophy patients only experience a single event, multiple bouts (ie, recurrences) occur in approximately 12% of patients and they may involve the same limb or the contralateral limb, and they may involve the same nerves or have a different distribution of nerve involvement.

 

• The interval between the bouts is unpredictable and can range from days to weeks (eg, with sequential bilateral involvement) to decades.

 

• When both sides are involved (ie, bilateral neuralgic amyotrophy), their involvement is sequential in the majority and simultaneous in the minority.

 

• Available evidence suggests that an autoimmune pathogenesis, likely related to a genetic susceptibility, most commonly generates an axon loss lesion (focal or multifocal) that involves predominantly motor axons.

 

• The motor axon predilection dictates the distribution and incidence of the lesions associated with neuralgic amyotrophy. Thus, pure motor nerves (including motor nerve branches to individual muscles) and predominantly motor nerves are much more frequently involved than are mixed nerves (Ferrante and Wilbourn 2017).

 

• Management of neuralgic amyotrophy consists of pain control and physical therapy. Although neuropathic pain medications are the mainstay, these medications take time to take effect. Thus, during the initial phase of the disorder when the pain is quite severe, opiates and corticosteroids are usually required.

Historical note and terminology

Historically, 2 separate disorders, serratus magnus paralysis and postinfectious paralysis, were described in the mid-1800s. The term serratus magnus paralysis reflected the muscle involved (the serratus magnus muscle, currently termed the serratus anterior muscle) and the term postinfectious paralysis indicated that the disorder followed an infection. Later that century, 2 other entities, serogenic neuropathy and vaccinogenic neuropathy, were reported. The terms applied to these latter 2 disorders reflected their presumed precipitation – serum administration and vaccine administration, respectively. A number of other entities were subsequently identified and labeled using terms appropriate to their presumed location, pathology, or trigger. In 1948, Parsonage and Turner recognized the unifying characteristics of these disorders, leading to their conclusion that all of these disorders represented a single entity with a variety of presentations (Parsonage and Turner 1948). In addition, Parsonage and Turner also coined the term neuralgic amyotrophy based on their recognition of these 2 quintessential clinical features – severe pain and significant muscle wasting. Following their report, the nondescriptive term Parsonage-Turner syndrome was added to the list of monikers. As stated above, of these terms, neuralgic amyotrophy and Parsonage-Turner syndrome are preferred because they do not suggest a specific lesion location, a specific trigger, or a specific pathology. Because neuralgic amyotrophy conveys its 2 most important clinical features, it is the term currently favored.

The content you are trying to view is available only to logged in, current MedLink Neurology subscribers.

If you are a subscriber, please log in.

If you are a former subscriber or have registered before, please log in first and then click select a Service Plan or contact Subscriber Services. Site license users, click the Site License Acces link on the Homepage at an authorized computer.

If you have never registered before, click Learn More about MedLink Neurology  or view available Service Plans.

Find out how you can join MedLink Neurology