Purpose: While dysarthria and dysphagia are known bulbar manifestations of amyotrophic lateral sclerosis (ALS), the relative prevalence of speech and swallowing impairments and whether these bulbar symptoms emerge at the same time point or progress at similar rates is not yet clear. We, therefore, sought to determine the relative prevalence of speech and swallowing impairments in a cohort of individuals with ALS and to determine the impact of disease duration, severity, and onset type on bulbar impairments.
Method: Eighty-eight individuals with a confirmed diagnosis of ALS completed the ALS Functional Rating Scale-Revised (ALSFRS-R), underwent videofluoroscopy (VF), and completed the Sentence Intelligibility Test (SIT) during a single visit. Demographic variables including disease duration and onset type were also obtained from participants. Duplicate, independent, and blinded ratings were completed using the Dynamic Imaging Grade of Swallowing Toxicity (DIGEST) scale and SIT to index dysphagia (DIGEST ≥ 1) and dysarthria (< 96% intelligible and/or < 150 words per minute) status. Descriptive statistics, Pearson chi-squared tests, independent-samples t tests, and odds ratios were performed.
Results: Dysphagia and dysarthria were instrumentally confirmed in 68% and 78% of individuals with ALS, respectively. Dysarthria and dysphagia were associated (p = .01), and bulbar impairment profile distributions in rank order included (a) dysphagia - dysarthria (59%, n = 52), (b) no dysphagia - dysarthria (19%, n = 17), (c) no dysphagia - no dysarthria (13%, n = 11), and (d) dysphagia - no dysarthria (9%, n = 8). Participants with dysphagia or dysarthria demonstrated 4.2 higher odds of exhibiting a bulbar impairment in the other domain than participants with normal speech and swallowing (95% CI [1.5, 12.2]). There were no differences in ALSFRS-R total scores or disease duration across bulbar impairment profiles (p > .05). ALSFRS-R bulbar subscale scores were significantly lower in individuals with dysphagia versus no dysphagia (8.4 vs. 10.4, p < .0001) and dysarthria versus no dysarthria (8.5 vs. 10.9, p < .0001). Dysphagia and onset type (p = .003) and dysarthria and onset type were associated (p < .0001).
Conclusions: Over half of the individuals with ALS in this study demonstrated both dysphagia and dysarthria. Of those with only one bulbar impairment, speech was twice as likely to be the first bulbar symptom to degrade. Future studies are needed to confirm these findings and determine the longitudinal progression of bulbar impairments in this patient population.