What Is Really New in Progressive Muscle Atrophy?

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.