Subglottic region: normal topography and possible clinical implications

A precise definition of clinically important laryngeal regions and compartments is still a matter of controversy. The often neglected subglottic area was reinvestigated in plastinated serial sections of 21 human adult specimens. The superior border of the subglottic region is defined by the transition of squamous stratified epithelium covering the vocal cords into the respiratory epithelium of the caudal airways. It is found at the inferior margin of the vocal fold at variable distance from the free edge of the vocal cord and bears a high risk of carcinogenesis. The anterior border of the subglottic region is the cricothyroid space between the thyroid cartilage and cricoid arch. Medially, it is bridged by the median cricothyroid ligament. Laterally, the gap between thyroid and cricoid cartilage is filled by adipose tissue in most cases. This provides a broad connection of intra- and extralaryngeal connective tissue. There, cancer may escape the larynx. The conus elasticus is often regarded as a firm fibroelastic membrane within the subglottic region, but its structure may be disturbed by piercing blood vessels or age-related changes, facilitating cancerous spread. The cricoid lamina representing the dorsal border of the subglottic space ossifies preferentially in its superior part, which is often attacked by tumor invasion. The inferior border of the subglottic region is defined at the inferior rim of the cricoid cartilage. At this level, the endocricoid submucosal tissue contains loosely arranged collagenous fibers, which probably do not act as an anatomic barrier.