Emedinews:Insights on Medicolegal Issues:Forensic anatomy and importance of larynx in postmortem examination

Medicolegal Update
(Dr Sudhir Gupta, Additional Prof, Forensic Medicine & Toxicology, AIIMS)

• The larynx consists of a large ‘V’–shaped thyroid cartilage. Below the smaller cricoid cartilage, at the upper margin of the posterior wing of the thyroid on each side, are the superior horns or ‘cornuae’, which are connected by the thyrohyoid membrane to the greater horns of the hyoid bone, which lies immediately above.
• The hyoid bone lies at the root of the tongue. The hyoid calcifies at variable times; the body is usually calcified, but the horns may calcify irregularly, both in space and time. In teenagers and young adults, they are usually cartilaginous and the joints mobile.
• In middle and later life, the hyoid and thyroid horns calcify and become more brittle.
• The cricoid cartilage is a modified upper tracheal ring but can also become partly calcified as age increases.
• No meaningful ages can be placed on any calcification, but traumatic fractures can occur at any time except in children and most teenagers.
• The pressure is mainly bilateral, so that the sides of the larynx are squeezed. Particularly vulnerable structures are the four ‘cornuae’ or horns, which protect backwards to maintain the patency of the airway around the glottis
• Lateral pressure of the fingers can displace any of the four horns inwards, either by direct pressure or by pressure on the thyrohyoid membrane, which then drags the horns medially. In young persons, the horns are so pliable that they return to their normal position on release of the pressure but, variably beyond the third decade, they may be sufficiently calcified to fracture.
• Though the hyoid bone has received most attention in publications as being the marker of violence to the larynx, in fact the thyroid horns are far more vulnerable. Simpson (1985) found that, in 25 successive deaths from manual strangulation, there were 22 fractures of thyroid horns but only one fractured hyoid.