[Pathogenesis and treatment of brachial plexus neuritis]

Neuralgic amyotrophy (NA, also known as Parsonage-Turner syndrome) is a distinct peripheral nervous system (PNS) disorder, characterized by sudden attacks of severe neuropathic pain usually in the shoulder and/or arm. The neuralgia commonly disappears after a few days to weeks, and consequently patchy paresis with amyotrophy appears. The available evidence suggests that NA is essentially idiopathic immune-mediated neuritis of the brachial plexus, and also has a complex pathogenesis that includes an underlying predisposition, susceptibility to dysfunction of some PNS structure, and a trigger for the attacks, such as viral infection, vaccination, trauma, surgery, and strenuous exercise. Genetic factors also contribute to the pathogenesis of NA, and thus, this disorder occurs in both idiopathic and hereditary forms, but hereditary one is considered to be 10 times less common than idiopathic one. NA has been considered to be self-limiting, benign disorder showing good recovery without specific treatments. However, recent studies have indicated that the long-term prognosis of NA is less favorable than has been assumed. In 2009, a Cochrane review identified one open label, retrospective series, the results of which suggested that administration of corticosteroids in the acute phase of NA could shorten the duration of painful symptoms and also accelerate recovery in some patients. We recently have reported that intravenous immunoglobulin (IVIg) with methylpredonisolone pulse therapy is effective for motor impairment of NA.