Neoplastic brachial plexopathy (NBP) is an uncommon diagnosis in most physiatrists' offices, but the condition bears review as it can mimic symptoms of many common upper limb neuropathies. Approximately 10% of all peripheral nerve lesions involve some type of brachial plexus lesion. Neoplastic invasion of the brachial plexus is an uncommon, though not rare, cause of plexopathy. This article reviews the more common issues associated with physiatric treatment of patients with NBP. 
Lesions of the brachial plexus occur most often secondary to neoplasms that reach the plexus by direct extension (Pancoast syndrome) or, more commonly, by metastasis through lymphatics from the axilla. Pain in the shoulder, radiating down the limb, may be observed, as well as pain in the medial forearm and hand with lower trunk innervation (C8-T1 roots) in some series. The most common pathophysiology revealed on electrodiagnostic tests is axonal loss. Peripheral pain mechanisms may include lowering of the nociceptor threshold by prostaglandins and other noxious chemical substances and persistent nociceptor stimulation. Compression or infiltration of the nerves of the plexus by a tumor may produce neuralgia and inflammation.
Approximately 14% of all upper limb neurologic lesions are due to brachial plexopathy of all types. Neoplastic plexopathies were responsible for 1.4 and 14.5% of symptoms in 2 series of patients who had undergone surgery. Insufficient data have been published to determine the frequency of NBP, but symptomatic NBP has been estimated to occur in 4% of patients with lung cancer and 2% of patients with breast cancer.
The international incidence of NBP is unknown.
In a single institution in Ireland, a 5-year retrospective study of 20 MRIs performed in patients with neoplasms, 6 (30%) confirmed a diagnosis of NBP. 
Incidence of metastatic neoplasm of the brachial plexus increases with age; thus, the condition is more common in elderly patients.
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