Thyroepiglotticus Muscle: Anatomy and Clinical Significance
Primary Function
The thyroepiglotticus muscle actively contributes to epiglottic downfolding during swallowing by exerting mechanical force on the epiglottis, working in concert with the aryepiglotticus muscle to facilitate airway protection. 1
Anatomical Structure and Mechanism
The thyroepiglotticus muscle is part of the active mechanism of epiglottic movement during deglutition, contrasting with purely passive mechanical theories:
Active vs. Passive Mechanisms: While passive theories focus solely on mechanical forces transmitted through the median hyoepiglottic ligament and pre-epiglottic adipose tissue, the active mechanism incorporates muscular contributions from both the aryepiglotticus and thyroepiglotticus muscles to achieve epiglottic downfolding 1
Timing of Action: Epiglottic downfolding occurs simultaneously with anterior hyoid bone displacement and thyrohyoid approximation during the swallow sequence 1
Lateral Ligamentous Support: Distinct fascial condensations (lateral hyoepiglottic ligaments) run from the lateral epiglottic edge to the hyoid bone near the greater horns, exerting preferential traction on the upper third of the epiglottis as the larynx elevates 1
Clinical Significance for Airway Protection
The thyroepiglotticus muscle functions as part of a coordinated airway protective system:
Coordinated Reflex Behaviors: The muscle participates in highly coordinated reflex behaviors including cough and swallow, whose common purpose is airway protection 2
Pharyngeal Coordination: The pharynx functions not as a passive space but as an active participant in airway protection, with muscles like the thyroepiglotticus contributing to this protective mechanism 2
Potential Clinical Implications
Dysfunction of the thyroepiglotticus muscle may contribute to aspiration risk in neurodegenerative diseases, though these mechanisms remain understudied in clinical populations:
Neurodegenerative Disease Risk: Impairment of airway protective mechanisms involving muscles like the thyroepiglotticus could lead to aspiration pneumonia in conditions affecting neuromuscular coordination 2
Dysphagia Consequences: Given that unilateral vocal fold immobility alone causes significant dysphagia (particularly to liquids) and aspiration pneumonia risk, combined dysfunction of multiple laryngeal structures including the thyroepiglotticus would likely compound these risks 3
Research Gap: These vital airway protective mechanisms involving the thyroepiglotticus have not been adequately evaluated in clinical conditions and require further study in both healthy and pathologic human populations 2
Common Clinical Pitfalls
Overlooking Active Muscular Contribution: Clinicians may incorrectly assume epiglottic movement is purely passive, missing potential muscular dysfunction as a cause of aspiration 1
Incomplete Swallowing Assessment: Standard dysphagia evaluations may not specifically assess thyroepiglotticus function, potentially missing a treatable component of aspiration risk 2