What is the role of neuralgic amyotrophy in the etiology of focal muscular atrophy (FMA)?

Updated: Feb 20, 2018
  • Author: Sridharan Ramaratnam, MD, MBBS; Chief Editor: Helmi L Lutsep, MD  more...
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Answer

Neuralgic amyotrophy

  • Neuralgic amyotrophy (brachial plexus neuritis) is characterized by extreme neuropathic pain and rapid multifocal weakness and atrophy in the upper limb.

  • Neuralgic amyotrophy has both an idiopathic and hereditary forms. The clinical presentations of idiopathic and hereditary forms are similar except for earlier age of onset and more recurrences in the hereditary form. Hereditary neuralgic amyotrophy is mainly linked to a mutation in the gene of the Septin-9 protein. [48]

  • The precise pathophysiological mechanisms are still unclear. In 55% of families with familial neuralgic amyotrophy, a point mutation or duplication in the SEPT9 gene on band 17q25 has been reported. A combination of factors, such as 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 response to the brachial plexus, may trigger the attacks. [49]

  • Evidence from one open-label retrospective series suggests that oral prednisone given in the first month after onset can shorten the duration of the initial pain and leads to earlier recovery in some patients.

  • Recovery is slow, in months to years, and many patients are left with residual pain and decreased exercise tolerance in the affected limb(s). [50]


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