Résumé :
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Communication n° 9 Objective : To assess the demographic and clinical features predicting a benign course in patients presenting with isolated amyotrophy of hands. Background : Patients with a clinical presentation of distal amyotrophy of arms are usually suspected to have amyotrophic lateral sclerosis. Hirayama disease is a much rarer benign disorder mainly of young males, with similar onset. Methods : Included patients had weakness and amyotrophy affecting at least two distal myotomes and two peripheral nerves territories in one or both upper limbs and lasting more than 12 months. We excluded patients with involvement of lower limbs, truncal or bulbar muscles, significant history of pain, sensory or autonomic features, UMN or cerebellar signs at presentation. Patients with a history of poliomyelitis or previous radiotherapy were excluded. All patients underwent clinical and electromyographic evaluation and cervical MRI (in neutral position). Most patients had anti-GM1 titers assessed. Results : After a follow-up of 3 to 8 years since onset, 8 patients still had a pure lower motor neuron syndrome restricted to the upper limbs. All were males, without a similar family history and onset between 15 and 33 years. In six patients the topography of amyotrophy (hand and forearm muscles sparing the brachioradialis), the cold effect and postural tremor suggest the diagnosis of bilateral (4) or unilateral (2) Hirayama syndrome. Conclusions : Early onset, male gender, cold aggravation and early postural tremor may be associated with a favorable outcome in patients with distal amyotrophy of hands. Hirayama disease is not uncommon in non-Asiatic populations and may often be bilateral. The astute peripheral neurologist's expertise is crucial in excluding ominous diagnoses like ALS and preventing useless (but not always harmless) "decompression" interventions.
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