Van den Berg-Vos and colleagues1 describe a prospective study in which they included a heterogeneous population of patients with motor neuron disease, including progressive muscle atrophy (PMA) and segmental distal and proximal muscular atrophy. During the follow-up period, 8 patients were diagnosed with PMA, 3 of whom developed respiratory failure. Although the authors did not refer to our work, we have previously described the outcomes of a group of 10 patients with PMA who were followed up prospectively for more than 12 months with serial clinical, respiratory, and neurophysiological evaluations.2 Patients who showed transcranial magnetic stimulation (TMS) abnormalities suggestive of a corticospinal tract lesion at study entry or who presented clinical signs of corticospinal tract lesion on follow-up were excluded from this group. We noted that patients with predominant axial weakness were more likely to progress to respiratory tract involvement. It would be useful if Van den Berg-Vos et al could confirm this finding in the patients with PMA that they have described.
de Carvalho M, Swash M. What Is Really New in Progressive Muscle Atrophy?. Arch Neurol. 2009;66(11):1427-1429. doi:10.1001/archneurol.2009.254