The conus elasticus (cricovocal membrane) is a fibroelastic membrane forming the lateral walls of the infraglottic larynx, extending from the upper border of the cricoid cartilage to the vocal ligaments above. It is thickened in the midline anteriorly as the median cricothyroid ligament, and its free upper borders form the vocal ligaments (the structural core of the vocal folds). The conus elasticus supports the inferior vocal folds and defines the subglottic airway.
Forms the lateral walls of the subglottic larynx, supports the vocal folds from below through its vocal ligament free borders, and maintains the patency of the subglottic airway against the external neck structures.
The median cricothyroid ligament, the thickened anterior midline portion of the conus elasticus, is the structure pierced in emergency cricothyrotomy and in elective tracheostomy as a landmark. Subglottic stenosis following prolonged intubation affects the conus elasticus level of the larynx, producing exertional dyspnoea and stridor. Transient or permanent subglottic stenosis is managed by endoscopic balloon dilation, laser resection, or laryngotracheal reconstruction with cartilage grafting.
In cannot-intubate-cannot-oxygenate airway emergencies, the median cricothyroid ligament (anterior conus elasticus) is incised or punctured to establish an emergency airway, identified by palpating the soft midline tissue between the thyroid and cricoid cartilages.
Chronic pressure necrosis from a tracheal tube cuff at the subglottic conus elasticus level causes fibrotic scarring and luminal narrowing, producing exertional dyspnoea and stridor with a characteristic hourglass or glottic web pattern on endoscopy and CT.
