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.
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%).
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.
To investigate whether primary lateral sclerosis (PLS) represents part of the amyotrophic lateral sclerosis-frontotemporal dementia (ALS-FTD) spectrum of diseases.