Can a horse break their tongue bone?

For this article, we will answer a very interesting question posed by one of our readers. Can a horse break their tongue bone?

What is the “tongue bone”?

In short, there is no bone present in the tongue itself; but the tongue is attached to a cage-like structure made up of multiple bones, called the hyoid apparatus. So, while strictly speaking they cannot break a bone in the body of the tongue, they can fracture one to which the tongue is attached. 

All about the Hyoid

The hyoid apparatus serves to alter the position and diameter of the larynx and nasopharynx; which allows the horse to take in as much air as possible when running at high speeds as well as supporting and connecting structures inside the head and throat. It is made up of pairs of bones called the stylohyoid, epihyoid, ceratohyoid and thyrohyoid bones and a single bone called the basihyoid. The tongue is attached to the hyoid apparatus by the basihyoid bone; and is also attached to the soft tissue structures of the back of the throat or pharynx. 

The tongue itself is made up of muscles, nerves and tendon

Movement of the tongue is critical in ingesting and chewing food. But as it is attached to the hyoid process, contraction of the muscles of the tongue will alter the shape of the hyoid apparatus; something that is important during high-speed exercise. The tongue contracts to force itself downwards to stabilise and dilate the airways of the nasopharynx, maximising air intake. This mechanism for dilating the airways is the basis behind the use of tongue ties in racehorses; although artificially tying the tongue down is not as useful as the active process of tongue depression by the horse itself. 

Like any bones, those in the hyoid apparatus are vulnerable to fracture or disease

Fractures of these bones are rare and only limited reports are available in the literature about such cases. The most common site of fracture is the stylohyoid bone, usually as a result of trauma or a disease called temporohyoid osteoarthropathy  (THO) which weakens the bone. 

It is important to be aware that clinical signs can vary greatly depending on the