Neuralgic Amyotrophy

BACKGROUND

Neuralgic amyotrophy (NA) is a multifactorial, monophasic neuritis that mainly affects the nerves of the shoulder girdle. It is characterized by very severe pain and by weakness that arises some time after the pain. Its reported incidence is high (100 cases per 100 000 persons per year), but our data suggest that many or most cases are diagnosed late or not at all.

METHODS

This review of the epidemiology, pathophysiology, diagnosis, and treatment of NA is based on pertinent publications retrieved by a selective literature search, and on data provided by the scientific institute of AOK, a German statutory health-insurance carrier.

RESULTS

It is currently thought that the combination of a genetic predisposition, an immunological trigger factor, and mechanical stress on the affected nerve segment(s) is pathophysiologically determinative. The prognosis of untreated NA is poor, with 25% of patients remaining unable to work at three years. The main form of treatment is with corticosteroids that are administered as early as possible. If there is evidence of nerve constriction or torsion, surgery may also help. There have only been six controlled cohort studies on the treatment of NA, and no randomized trials. It is not uncommon for the acute phase to develop into a chronic pain syndrome requiring multidimensional treatment.

CONCLUSION

Particularly in view of the high incidence and improved therapeutic options, NA should be included in the differential diagnosis of all patients with suggestive symptoms.

[Diagnostics and treatment of hourglass-like nerve constrictions and torsions in neuralgic amyotrophy]

Neuralgic amyotrophy is a disease of the peripheral nervous system characterized by severe neuropathic pain followed by peripheral paralysis. A distinction is made between a hereditary and an idiopathic form, which is assumed to have an autoimmunological origin. Conservative medicinal treatment mainly consists of nonsteroidal anti-inflammatory drugs (NSAID), opioids and glucocorticoids; however, despite treatment, symptoms in the form of pain or paralysis persist in over 50% of cases. Inflammation can lead to strictures and torsions of peripheral nerves, which can be visualized by imaging using nerve sonography or magnetic resonance (MR) neurography and confirmed intraoperatively during surgical exploration. Based on the currently available data, patients with strictures and torsions of peripheral nerves can benefit from neurosurgical treatment.

Neuralgic amyotrophy detected by magnetic resonance neurography: subclinical, bilateral, and multifocal brachial plexus involvement

INTRODUCTION

Neuralgic amyotrophy (NA) is a painful non-traumatic peripheral nervous system condition affecting the brachial plexus. Signal abnormalities in nerves and muscles have been detected in these patients using magnetic resonance neurography (MRN).

METHODS

Electronic medical records and MRN images obtained in a 3 T scanner, in 14 adult patients diagnosed with NA at our Neurological institution (Neuromuscular Disorders Section), between December 2015 and December 2019 were retrospectively reviewed. The study was first approved by our Institutional Ethics Committee.

RESULTS

Subclinical, multifocal, and bilateral nerve signal anomalies were recorded in the brachial plexus of these patients. We identified four different types of nerve constriction without entrapment, which we categorized as follows: incomplete focal (type I), complete focal or hourglass (type II), multifocal or string of pearls (type III) and segmental (type IV).

CONCLUSIONS

Given that MRN is an accurate diagnostic tool to detect nerve damage, we believe abnormal findings could improve early detection of NA patients.

A standardized ultrasound approach in neuralgic amyotrophy

Neuralgic amyotrophy (NA), also referred to as idiopathic brachial plexitis and Parsonage-Turner syndrome, is a peripheral nerve disorder characterized by acute severe shoulder pain followed by progressive upper limb weakness and muscle atrophy. While NA is incompletely understood and often difficult to diagnose, early recognition may prevent unnecessary tests and interventions and, in some situations, allow for prompt treatment, which can potentially minimize adverse long-term sequalae. High-resolution ultrasound (HRUS) has become a valuable tool in the diagnosis and evaluation of NA. Pathologic HRUS findings can be grouped into four categories: nerve swelling, swelling with incomplete constriction, swelling with complete constriction, and fascicular entwinement, which may represent a continuum of pathologic processes. Certain ultrasound findings may help predict the likelihood of spontaneous recovery with conservative management versus the need for surgical intervention. We recommend relying heavily on history and physical examination to determine which nerves are clinically affected and should therefore be assessed by HRUS. The nerves most frequently affected by NA are the suprascapular, long thoracic, median and anterior interosseous nerve (AIN) branch, radial and posterior interosseous nerve (PIN) branch, axillary, spinal accessory, and musculocutaneous. When distal upper limb nerves are affected (AIN, PIN, superficial radial nerve), the lesion is almost always located in their respective fascicles within the parent nerve, proximal to its branching point. The purpose of this review is to describe a reproducible, standardized, ultrasonographic approach for evaluating suspected NA, and to share reliable techniques and clinical considerations when imaging commonly affected nerves.

Update on classification, epidemiology, clinical phenotype and imaging of the nonsystemic vasculitic neuropathies

PURPOSE OF REVIEW

Single-organ vasculitis of the peripheral nervous system (PNS) is often designated nonsystemic vasculitic neuropathy (NSVN). Several variants or subtypes have been distinguished, including migratory sensory neuropathy, postsurgical inflammatory neuropathy, diabetic radiculoplexus neuropathies, skin-nerve vasculitides, and, arguably, neuralgic amyotrophy. NSVN often presents as nondiabetic lumbosacral radiculoplexus neuropathy (LRPN). This review updates classification, clinical features, epidemiology, and imaging of these disorders.

RECENT FINDINGS

A recent study showed the annual incidence of LRPN in Olmstead County, Minnesota to be 4.16/100 000:2.79/100 000 diabetic and 1.27/100 000 nondiabetic. This study was the first to determine the incidence or prevalence of any vasculitic neuropathy. In NSVN, ultrasonography shows multifocal enlargement of proximal and distal nerves. In neuralgic amyotrophy, MRI and ultrasound reveal multifocal enlargements and focal constrictions in nerves derived from the brachial plexus. Histopathology of these chronic lesions shows inflammation and rare vasculitis. Diffusion tensor imaging of tibial nerves in NSVN revealed decreased fractional anisotropy in one study.

SUMMARY

Single-organ PNS vasculitides are the most common inflammatory neuropathies. Neuralgic amyotrophy might result from PNS vasculitis, but further study is necessary. The usefulness of focal nerve enlargements or constrictions in understanding pathological mechanisms, directing biopsies, and monitoring disease activity in NSVN should be further investigated.

Development of Parsonage-Turner Syndrome After Heat Stroke in Firefighters: A Report of 2 Cases

CASE

Two firefighters developed Parsonage-Turner syndrome (PTS) shortly after sustaining episodes of heat stroke. Patient 1 was a 40-year-old man who presented with shoulder pain and supraspinatus and infraspinatus weakness. Patient 2 was a 35-year-old man who presented with shoulder pain and absent external rotation strength. Both had electrodiagnostic testing and magnetic resonance imaging findings consistent with PTS. Both demonstrated partial but incomplete recovery at 1- and 2.5-year follow-ups, respectively.

CONCLUSIONS

PTS should remain on the differential diagnosis for any patient presenting with sudden onset shoulder pain and neurological deficits after an episode of heat-related illness.