[citation needed] In contrast to amyotrophic lateral sclerosis or primary lateral sclerosis, PMA is distinguished by the absence of:[citation needed] The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons.

The occurrence of upper motor neuron symptoms such as brisk reflexes, spasticity, or a Babinski sign would indicate a progression to ALS; the correct diagnosis is also occasionally made on autopsy.

[1] Despite being rarer than ALS, PMA was described earlier, when in 1850 French neurologist François Aran described 11 cases which he termed atrophie musculaire progressive.

Contemporary neurologist Guillaume-Benjamin-Amand Duchenne de Boulogne English: /duːˈʃɛn/ also claimed to have described the condition 1 year earlier, although the written report was never found.

[citation needed] Since its initial description in 1850, there has been debate in the scientific literature over whether PMA is a distinct disease with its own characteristics, or if lies somewhere on a spectrum with ALS, PLS, and PBP.

Such views still exist in archaic terms for PMA such as "Primary progressive spinal muscular atrophy".