[Lower motor neuron diseases with predominantly upper limbs affection: are they independent forms or atypical variants of amyotrophic lateral sclerosis?].

We carried out an analysis of 5 sporadic cases of lower motor neuron disease with predominant affection of the proximal parts of arms in 2 patients and distal parts in 3 patients. From clinical point of view, our own observations, along with similar cases reported in the literature with predominantly affected upper limbs, different progression of the disease and denervation changes during needle EMG, can argue for clinical heterogeneity of lower motor neuron disease. There were some difficulties in establishment of a differential diagnosis between atypical variants of amyotrophic lateral sclerosis ("flail arm" syndrome) and primary muscular atrophy of adults at the early stages of the disease. We suppose that atypical variants of amyotrophic lateral sclerosis resultant from affection of lower motor neuron only ("flail arm" syndrome and distal amyotrophy), could be distinguished from amyotrophic lateral sclerosis and considered as an independent entity.