Plateaus in amyotrophic lateral sclerosis progression: results from a population-based cohort

Background and purpose The aim was to assess the frequency of plateaus in amyotrophic lateral sclerosis (ALS) progression using a large population-based cohort. Methods Data from the Piemonte and Valle d'Aosta ALS register were used. Patients who were diagnosed between 2007 and 2014 were considered. The follow-up period was extended until 31 December 2018. Visits after tracheostomy were excluded. A plateau was defined as a stable Amyotrophic Lateral Sclerosis Functional Rating Scale revised (ALSFRSr) score lasting at least 6, 12 or 18 months. Results Out of 1214 patients, 200 (16.5%), 93 (7.7%) and 52 (4.3%) showed at least one plateau lasting a minimum of 6, 12 and 18 months, respectively. Plateaus occurred mostly at high ALSFRSr scores and were more frequent during the initial phases of the disease course. Spinal onset [odds ratio (OR) 1.83, 95% confidence interval (CI) 1.16-2.95, P value 0.01) and predominant upper motor neuron phenotype (OR 2.18, 95% CI 1.36-3.48, P value 0.001) conferred a higher risk for the subsequent appearance of plateaus; conversely, older age at diagnosis (OR 0.25, 95% CI 0.11-0.54, P value 0.002 for >75 year age class) reduced this risk. Conclusions Plateaus in ALS progression lasting at least 6 months appear in about one out of six patients and could last even 12, 18 months or more in a smaller subgroup of patients. Plateau occurrence should not lead the neurologist to automatically reconsider ALS diagnosis and should be considered for future clinical trial design.