Associations between laryngeal and cough dysfunction in motor neuron disease with bulbar involvement

Abstract

PURPOSE: Cough, a fundamental mechanism in airway protection, depends on true vocal fold (TVF) function and airflow. In individuals with motor neuron disease (MND), cough impairment leads to increased risk for aspiration and respiratory failure. This study characterizes differences and associations between TVF kinematics and airflow during cough in individuals with bulbar MND. METHODS: Sequential glottal angles associated with TVF adduction and abduction across the phases of volitional cough were analyzed from laryngeal videoendoscopy exams of adults with bulbar MND (n=12) and healthy age-matched controls (n=12) and compared with simultaneously collected cough-related airflow measures. RESULTS: Significant differences between MND and control subjects were observed with the following airflow and TVF measures: peak expiratory cough flow (PECF) (p=0.01), expiratory phase rise time (EPRT) (p=0.004), volume acceleration (p=<0.001), maximum TVF angle during expulsion phase post-compression abduction (approached significance p=0.06), and expulsion phase post-compression abduction TVF angle average velocity (p=0.003). All subjects demonstrated complete TVF and supraglottic closure during the compression phase of cough, except 2/12 MND subjects demonstrated incomplete supraglottic closure. Maximum post-compression TVF abduction angle and post-compression TVF abduction angular velocity were statistically correlated with PECF (r = 0.49; p = 0.02) and EPRT(r = -0.66); p = 0.001), respectively, when data were analyzed for MND and control participants combined. However this may represent artifact owing to the variable distributions in each group. Correlational analyses for the groups separately were not statistically significant, except the correlation between post-compression maximum TVF abduction angle and PECF demonstrated a strong positive relationship and approached significance in the MND group (r = 0.57; p = 0.09). CONCLUSIONS: Reductions in the speed and extent of TVF abduction are seen during expulsion phase of cough in individuals with MND. This may contribute to cough impairment and morbidity.