Neuralgic amyotrophy

Neuralgic amyotrophy (NA), also known as Parsonage-Turner syndrome, brachial plexus neuritis, or idiopathic brachial plexopathy, is a peripheral nervous system disorder characterized by sudden onset of severe pain in the shoulder and upper arm, followed by weakness, muscle wasting (amyotrophy), and sensory changes in the affected limb. The condition primarily affects the brachial plexus — the network of nerves that controls movement and sensation in the shoulder, arm, and hand — though involvement of nerves outside the brachial plexus (such as the lumbosacral plexus, phrenic nerve, or cranial nerves) can also occur. Episodes are often preceded by triggers such as infections, surgery, vaccinations, strenuous exercise, or emotional stress, though many cases have no identifiable precipitant. Neuralgic amyotrophy exists in two forms: an idiopathic (sporadic) form, which is more common, and a hereditary form (hereditary neuralgic amyotrophy, HNA), which is inherited in an autosomal dominant pattern and is associated with mutations in the SEPT9 gene (also known as Septin-9) on chromosome 17q25. Hereditary NA tends to present at a younger age and with recurrent episodes. The hallmark clinical course begins with acute, excruciating pain lasting days to weeks, followed by patchy weakness and atrophy of shoulder girdle and upper arm muscles, most commonly the serratus anterior, supraspinatus, infraspinatus, and deltoid muscles. Sensory deficits, though often less prominent, may affect the lateral aspect of the shoulder or forearm. Recovery is typically slow, occurring over months to years, and while most patients regain significant function, a substantial proportion experience residual pain, weakness, or fatigue. Treatment is primarily supportive. In the acute phase, pain management with analgesics (including opioids and neuropathic pain medications such as gabapentin or amitriptyline) is essential. Oral corticosteroids are sometimes used early in the course, though evidence for their efficacy remains limited. Physical therapy and rehabilitation play a central role in recovery, focusing on maintaining range of motion and gradually rebuilding strength. There is currently no disease-modifying therapy, and management of hereditary NA follows the same principles as the sporadic form. Prognosis is generally favorable, but recovery can be incomplete, particularly in patients with recurrent attacks.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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