Because of its distinct symptoms, it was suggested that VBS is a separate entity, different from ALS.
The disease was described first in 1886 by the French neurologist Alfred Vulpian and the German neuropathologist Martin Bernhardt as a progressive weakness of the upper limbs but bulbar muscles unaffected.
At later stages, weakening of lower limbs and other ALS symptoms were observed.
16 per cent of these flail arm syndrome cases survived more than ten years, the highest of all variants of ALS in the study.
One of the few people with brachial amyotrophic diplegia who has spoken in public about the disease is Sonia Bustamante Dominguez, a Mexican woman who showed the first symptoms in 2012 and was diagnosed in 2016.