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 (F _1,11=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.