Associations Between Laryngeal and Cough Dysfunction in Motor Neuron Disease with Bulbar Involvement
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True vocal fold (TVF) dysfunction may lead to cough ineffectiveness. In individuals with motor neuron disease (MND), cough impairment in the context of dysphagia increases risk for aspiration and respiratory failure. This study characterizes differences and associations between TVF kinematics and airflow during cough in individuals with bulbar MND. Sequential glottal angles associated with TVF movements during volitional cough were analyzed from laryngeal video endoscopy examinations of adults with bulbar MND (n = 12) and healthy controls (n = 12) and compared with simultaneously collected cough-related airflow measures. Significant group differences were observed with airflow and TVF measures: volume acceleration (p ≤ 0.001) and post-compression abduction TVF angle average velocity (p = 0.002) were lower and expiratory phase rise time (p = 0.001) was higher in the MND group. Reductions in maximum TVF angle during post-compression abduction in the MND group approached significance (p = 0.09). All subjects demonstrated complete TVF and supraglottic closure during the compression phase of cough, except for incomplete supraglottic closure in 2/12 MND participants. A strong positive relationship between post-compression maximum TVF abduction angle and peak expiratory cough flow was observed in the MND group, though it was not statistically significant (r = 0.55; p = 0.098). Reductions in the speed and extent of TVF abduction are seen during the expulsion phase of cough in individuals with MND. This may contribute to cough impairment and morbidity.
KeywordsMotor neuron disease (MND) Cough Laryngeal function True vocal folds (TVFs) Amyotrophic lateral sclerosis (ALS) Primary lateral sclerosis (PLS) Deglutition Deglutition disorders
We thank the individuals with MND and healthy control participants who took part in this study. Many thanks also to James Kobler, PhD, Harvard Medical School, for the use of his custom angle-marking Matlab code. In addition, many thanks to Carolyn Baylor, PhD, for her help and expertise with reliability measures. This study was supported by NIH/NIDCD F31 DC011689 (2011–2012) and in part by the Walter C. and Anita C. Stolov Research Fund (2010–2011).
Conflict of interest
The authors have no conflicts of interest to declare.
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