Objectives: Aspiration after stroke has been associated with aspiration pneumonia, which contributes to increased mortality of stroke. Laryngeal elevation is a core mechanism for protection from aspiration. Few studies have explored the predictive value of laryngeal elevation velocity for aspiration after stroke. This study aimed to explore the ability of laryngeal elevation velocity to predict aspiration in patients with acute ischemic stroke.
Methods: This was a prospective cohort study that included consecutive acute ischemic stroke patients treated at a teaching hospital during a 10-month period. Patients underwent magnetic resonance imaging (MRI) to confirm the diagnosis of acute ischemic stroke. Patients who were at risk of aspiration and could swallow 5 ml of diluted barium (40%, w/v) for a videofluoroscopic swallowing (VFS) study were included. The association between abnormal indices in the oral and pharyngeal phase of the VFS study and aspiration was examined using univariate analyses. These indices included the lip closure, tongue movement and control, laryngeal elevation velocity and range, the latency of pharyngeal swallowing, pharyngeal transit time (PTT), abnormal epiglottis tilt, residual barium in the pharynx, and the duration of upper esophageal sphincter (UES) opening. The laryngeal elevation velocity (%/s) was calculated as the range of laryngeal elevation (%) from the resting position to the maximum superior position or to the position where the laryngeal vestibule is fully closed divided by the corresponding duration of laryngeal elevation. The range of laryngeal elevation (%) was the percentage calculated as the distance between the resting laryngeal position and the maximum superior excursion position or position where the laryngeal vestibule is fully closed divided by the distance between the resting laryngeal position and the lowest edge of the mandible. A logistic regression analysis was used to determine the predictive value for aspiration secondary to reduced laryngeal elevation velocity after adjusting for the effects of other indices. Intrarater and interrater reliability were calculated using Pearson's correlation coefficients.
Results: Data from 89 patients were analyzed. This cohort included 71 males and 18 females with a mean age of 59.31±11.46 years. The mean time from stroke onset to the VFS study was 3 days (1-7). Twenty one (23%) patients aspirated while swallowing 5 ml of diluted barium (40%, w/v). Aspiration was associated with age, the velocity (%/s) of laryngeal elevation and duration, delayed pharyngeal phase, pharyngeal transit time, abnormal epiglottic tilt, and invalid laryngeal elevation before true swallowing, and duration of upper esophageal sphincter (UES) opening. After adjusting for the effects of the indices mentioned above, logistic regression analysis revealed that a reduced of laryngeal elevation velocity before vestibule closure was predictive of aspiration independently (OR, 0.993; 95% CI, 0.987-1.000).
Discussions: Reduced laryngeal elevation velocity for laryngeal elevated to position where laryngeal vestibule is fully closed was an independent predictor of aspiration in patients with acute ischemic stroke. This may be related to a decreased contraction velocity of the muscles involved in hyolaryngeal elevation. Therapeutic methods aimed at improving laryngeal elevation velocity may decrease aspiration events and pneumonias after stroke.