Can amyotrophic lateral sclerosis progression really pause? A cohort study using the medical research council scale

Objective: To assess the frequency and predictors of plateaus in ALS progression as assessed by the Medical Research Council (MRC) Scale. Methods: All patients attending the ALS Center of Turin, with a diagnosis between 2007 and 2014 were considered. At each visit, muscle strength was evaluated in several muscles and assessed using the MRC scale. Concomitant ALSFRSr scores were retrieved. Plateaus were calculated as a stable overall MRC or ALSFRSr score lasting at least 6, 12 or 18 months. Results: According to MRC scale scores, 122 (22.8%), 71 (13.2%) and 59 (11.0%) patients experienced a plateau lasting at least 6, 12 and 18 months. ALSFRSr scores revealed similar estimates [134, (25.0%), 89 (16.6%) and 67 (12.5%), respectively]. Plateaus were more frequent at high scores and appeared a median of 24.6 months (IQR 6.7-47.7) after the diagnosis. Only the predominant upper motor neuron phenotype (OR 4.06, 95% CI 2-06-8.10, p-value <0.001) and diagnostic delay OR 1.03, 95% CI 1.01-10.5, p-value = 0.005) were significantly correlated with their appearance. Discussion: Plateaus in ALS progression as assessed using either ALSFRSr or MRC scale are not infrequent and should be expected especially in less aggressive phenotypes. Similar results were found both using the MRC scale and the ALSFRSr scores, suggesting a comparable reliability of these scales in grasping the disease progression.