To investigate whether primary lateral sclerosis (PLS) represents part of the amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) spectrum of diseases.
As of 20th January 2017, the MND Quality Registry included 99% of the MND patients of the Stockholm area (N = 194), consisting mostly of ALS patients (N = 153, 78.9%), followed by patients labeled as MND due to a neurophysiology finding but not fulfilling the criteria for ALS (N = 20, 10.3%), primary lateral sclerosis (N = 13, 6.7%), and progressive spinal muscular atrophy patients (N = 8, 4.1%).
The pathomechanism of sporadic amyotropic lateral sclerosis is not clearly understood, although a proportion of familial amyotropic lateral sclerosis is caused by superoxide dismutase 1 mutations.
Primary lateral sclerosis (PLS) is a diagnosis of exclusion in patients with progressive spinobulbar spasticity and could be part of the clinical spectrum of ALS.