Association between dysarthria and cognitive impairment in ALS: A prospective study

Several studies have demonstrated impaired cognition in amyotrophic lateral sclerosis (ALS) patients, but it has been difficult to identify risk factors for this impairment. An association between cognitive changes and bulbar site of onset or dysarthria has been suggested, but the findings are variable. We tested for both associations in a large cohort of ALS patients. At the time of diagnosis of sporadic ALS, all patients (n=355) in this prospective study underwent comprehensive neuropsychological testing. In addition, a subset of 175 patients underwent a detailed assessment of dysarthria, which was quantified using the Appel ALS Score (AALSS). ALS patients with bulbar site of onset performed significantly worse than limb onset patients on a few timed ((VSAT-time, p<0.05), (Stroop Color, p<0.05), (Stroop Word, p<0.05)) tests of frontal lobe functions, but the significance could not be replicated when motor impairment was accommodated into the tests ((VSAT-errors, p=0.73), (Stroop interference, p=0.08)). ALS patients with dysarthria performed significantly worse than non-dysarthrics on multiple timed ((BD, p<0.05), (VSAT-time, p<0.05), (Stroop Color, p<0.05), (Stroop Word, p<0.05), (Trails A, p<0.05), (Trails B, p<0.05)) neuropsychological tests, and the significance was maintained when motor impairment was accommodated into one of these tests (Stroop interference, p<0.05). Additionally, dysarthrics performed significantly worse on two untimed measures of cognition ((Similarities, p<0.05), (Rey Copy, p<0.05)). Cognitive functioning in ALS does not associate with the site of onset and has a moderate association with dysarthria.