Does primary lateral sclerosis exist? A study of 20 patients and a review of the literature

The question of whether primary lateral sclerosis (PLS) is a nosological en tity distinct from amyotrophic lateral sclerosis (ALS) has been the subject of controversy since it was first described in the nineteenth century. PLS has been defined as a rare, non-hereditary disease characterized by progre ssive spinobulbar spasticity, related to the selective loss of precentral p yramidal neurones, with secondary pyramidal tract degeneration and preserva tion of anterior horn motor neurones. In the recent clinical literature, th e frontier between ALS and neurodegenerative disease remains poorly defined . We studied 20 patients with a diagnosis of PLS. We carried out a variety of tests in order to determine the presence of a more diffuse neurodegenera tive process. We also performed a longitudinal electrophysiological evaluat ion. Our clinical, electrophysiological. and pathological investigations pr ovide evidence that the disease has a heterogeneous clinical presentation a nd that degeneration is not restricted to the central motor system.