We investigated the symptoms, course and prognosis of neuralgic amyotrophy (NA) in a large group of patients with idiopathic neuralgic amyotrophy (INA, n = 199) and hereditary neuralgic amyotrophy (HNA, n = 47) to gain more insight into the broad clinical spectrum of the disorder. Several findings from earlier smaller-scale studies were tested, and for the first time the potential differences between the hereditary and idiopathic phenotypes and between males and females were explored. Generally, the course of the pain manifests itself in three consecutive phases with an initial severe, continuous pain lasting for approximately 4 weeks on average. Sensory involvement was quite common and found in 78.4% of patients but was clinically less impairing than the initial pain and subsequent paresis. As a typically patchy disorder NA can affect almost any nerve in the brachial plexus, although damage in the upper and middle trunk distribution with involvement of the long thoracic and/or suprascapular nerve occurred most frequently (71.1%). We found no correlation between the distribution of motor and sensory symptoms. In INA recurrent attacks were found in 26.1% of the patients during an average 6 year follow-up. HNA patients had an earlier onset (28.4 versus 41.3 years), more attacks (mean 3.5 versus 1.5) and more frequent involvement of nerves outside the brachial plexus (55.8 versus 17.3%) than INA patients, and a more severe maximum paresis, with a subsequent poorer functional outcome. In males the initial pain tended to last longer than it did in females (45 versus 23 days). In females the middle or lower parts of the brachial plexus were involved more frequently (23.1 versus 10.5% in males), and their functional outcome was worse. Overall recovery was less favourable than usually assumed, with persisting pain and paresis in approximately two-thirds of the patients who were followed for 3 years or more.

In this review we provide a current overview of the clinical features, pathophysiology, epidemiology, and diagnostic and therapeutic strategies in neuralgic amyotrophy (NA). The disorder has several phenotypic variations, with a classic form in 70% of the patients. It is not rare, with an incidence of 1 per 1,000 individuals, but it is still often missed. Recurrences are common, yet the proposed multifactorial etiology, which includes genetic, biomechanical, and immunologic factors, limits our capacity to predict or prevent them. NA is a clinical diagnosis, and ancillary studies serve to exclude infectious or malignant causes or to assess a differential diagnosis. If patients are seen early and are still in pain, a short trial of high-dose oral corticosteroids is advised, and adequate analgesia may require opioids and non-steroidal anti-inflammatory drugs. Persistent complaints are common, and a multidisciplinary rehabilitation approach focusing on scapular coordination, energy distribution strategies, and self-management is indicated.

Neuralgic amyotrophy--also known as Parsonage-Turner syndrome or brachial plexus neuritis--is a distinct and painful peripheral neuropathy that causes episodes of multifocal paresis and sensory loss in a brachial plexus distribution with concomitant involvement of other PNS structures (such as the lumbosacral plexus or phrenic nerve) in a large number of patients. The phenotype can be limited or extensive and the amount of disability experienced also varies between patients, but many are left with residual disabilities that affect their ability to work and their everyday life. Both idiopathic and hereditary forms exist. The latter form is genetically heterogeneous, but in 55% of affected families, neuralgic amyotrophy is associated with a point mutation or duplication in the SEPT9 gene on chromosome 17q25. The disease is thought to result from an underlying genetic predisposition, a susceptibility to mechanical injury of the brachial plexus (possibly representing disturbance of the epineurial blood-nerve barrier), and an immune or autoimmune trigger for the attacks. The precise pathophysiological mechanisms are still unclear; treatment is empirical, and preventive measures are not yet available. This Review provides an overview of the current clinical and pathophysiological concepts and research topics in neuralgic amyotrophy.

Muscle ultrasound is a convenient technique to visualize normal and pathological muscle tissue as it is non-invasive and real-time. Neuromuscular disorders give rise to structural muscle changes that can be visualized with ultrasound: atrophy can be objectified by measuring muscle thickness, while infiltration of fat and fibrous tissue increase muscle echo intensity, i.e. the muscles become whiter on the ultrasound image. Muscle echo intensity need to be quantified to correct for age-related increase in echo intensity and differences between individual muscles. This can be done by gray scale analysis, a method that can be easily applied in daily clinical practice. Using this technique it is possible to detect neuromuscular disorders with predictive values of 90 percent. Only in young children and metabolic myopathies the sensitivity is lower. Ultrasound is a dynamic technique and therefore capable of visualizing normal and pathological muscle movements. Fasciculations can easily be differentiated from other muscle movements. Ultrasound appeared to be even more sensitive in detecting fasciculations compared to EMG and clinical observations, because it can visualize a large muscle area and deeper located muscles. With improving resolution and frame rate it has recently become clear that also smaller scale spontaneous muscle activity such as fibrillations can be detected by ultrasound. This opens the way to a broader use of muscle ultrasound in the diagnosis of peripheral nerve and muscle disorders.

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Mild-to-moderate neuromuscular involvement is common in various types of EDS, with a remarkable relation between residual TNX level and degree of neuromuscular involvement, compatible with a dose-effect relation. The findings of this study should increase awareness of neuromuscular symptoms in EDS patients and improve clinical care. They also point to a role of the extracellular matrix in muscle and peripheral nerve function.

Neuralgic amyotrophy is a distinct clinical syndrome with acute severe pain and patchy paresis in the shoulder and arm region. The clinical phenotype was recently found to be more comprehensive and the long-term prognosis less optimistic than usually assumed for many patients. The disorder can be idiopathic or hereditary in an autosomal dominant fashion, with only few phenotypical variations between the two. This article provides a practical overview of current knowledge on the clinical presentation, diagnosis, pathogenesis and the treatment of pain and complications.