title: Non-progressive juvenile spinal muscular atrophy of the distal upper limb (Hirayama's disease): a clinical variant of the benign monomelic amyotrophy.
abstract: Hirayama's disease (HD) is frequently found in Asia, and is rarely referred among westerners. It affects young people with higher incidence in males. It is a focal distal amyotrophy with unilateral or asymmetric bilateral involvement of C7, C8 and T1 innervated muscles. HD appears sporadically and has a benign evolution with clinical stabilization in around one year. We report four young male patients with clinical and electrophysiological alterations described in HD, which were followed-up during 5 years. Electromyographic findings were indicative of lower motor neuron involvement. We analyzed cervical MRI aiming at understanding if a questionable spinal cord compression could be implicated in the pathogenesis, but no abnormality was verified. In view of its clinical, and EMG characteristics, HD is no more than a benign monomelic amyotrophy (BMA) clinical variant, and not a specific disease. This eponym could be considered only for the distal upper limb variant (Hirayama's variant) of the BMA.
authors.affiliation: Department of Neurology, Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil.
authors.forename: O J
authors.initials: OJ
authors.lastname: Nascimento
authors.forename: M R
authors.initials: MR
authors.lastname: Freitas
mesh_terms: D000328:Adult; D004576:Electromyography; D005542:Forearm / Q000473:pathology*; D006225:Hand / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014897:Spinal Muscular Atrophies of Childhood / Q000473:pathology*