Assessing the Effect of Fatigue on Swallowing Function in Adults with Acute Stroke. A Pilot Study

Objective: To determine if fatigue systematically effects the timing of swallowing events and to discuss underlying causes of fatigue other than peripheral neuromuscular fatigue. Design: Pre-post within-subject repeated-measures design. Setting: General acute care hospital and designated stroke center. Participants: Thirteen patients (10 males and 3 females) aged 52-80 years (mean 64.84 9.58 y) with acute stroke and clinically suspected dysphagia. Interventions: Under videofluoroscopy, each participant swallowed a pre- and post-study 1-mL liquid barium bolus and, in an attempt to fatigue the system, 30-45 additional bolus trials of varying amounts (ie, 5 mL, 10 mL, and bite-sized) and consistencies (ie, International Dysphagia Diet Standardisation Initiative Level 0-7). Main Outcome Measures: Six temporal sequences (ie, oral, pharyngeal, and pharyngeal delay transit times and durations of laryngeal vestibule closure, cricopharyngeal opening, and laryngeal elevation) for 1-mL liquid boluses were measured pre- and postvideofluoroscopic swallowing study and compared. Results: Findings indicated that only 2 of the 6 temporal factors yielded significant differences pre- to post fatigue. The postvideofluoroscopic 1-mL liquid swallow took longer than the pre-videofluoroscopic 1-mL liquid swallow in terms of pharyngeal transit (1,11=5.362, P =.046) and pharyngeal delay time (F1,11=5.228, P =.048). Conclusions: These findings indicate that peripheral neuromuscular fatigue is unlikely to be the primary cause of the observed changes, as only 2 of the 6 temporal measures-pharyngeal transit time and pharyngeal delay time-were affected. In cases of peripheral neuromuscular fatigue, one would expect increases across all 6 timing measures due to the integrated nature of the swallowing process. Instead, the results suggest that the inconsistencies may stem from a delayed excitatory response of neurons or a delay in synaptic transmission within the nucleus tractus solitarius, potentially associated with stroke. This delay likely contributes to the prolongation of both pharyngeal transit and pharyngeal delay times. Thus, a model focused solely on peripheral neuromuscular fatigue does not fully account for the findings, highlighting the importance of considering central neural mechanisms in the clinical evaluation of swallowing disorders. (c) 2024 The Authors. Published by Elsevier Inc. on behalf of American Congress of Rehabilitation Medicine. This is an open access article under the CC BY-NC-ND license (http://creativecommons. org/licenses/by-nc-nd/4.0/).