Dentigerous Cysts - Tooth in Ear

Horse ear
Unless the cyst is causing discomfort or becomes infected, surgery may not be necessary. Image: John Slater/Getty Images

What is a tooth in the ear? It sounds gruesome.  How could there be such a thing is a tooth in a horse’s ear? It's just a myth, right?  As it turns out, this is a real, but rare condition and doesn’t just occur in a horse’s ear. Although it’s most usual to find these cysts on the horse’s head and jaw, they can occur anywhere. Dentigerous cysts are congenital, which means that if your horse has one, it was born with it.

And as alarming as it sounds, they are rarely dangerous with good hygiene. Because they are rare, you probably won’t see a lot of them, but you won’t be surprised if someone mentions their horse has a tooth in its ear.

Other Names

ear teeth, erratic tooth, dentigerous cysts, heterotrophic polydontia, temporal odontoma, temporal teratoma, tooth in ear

Symptoms

A dentigerous cyst can appear as a firm swelling at the base of a young horse’s ear, or under the jaw. There may be a channel that drains a sticky, pale fluid from the swelling. The cysts may be invisible until infection sets in. The cysts can also form in the horse’s nasal passages, where they can cause either a constriction or pressure that is uncomfortable for the horse. Occasionally, these cysts may be found on other areas of the body.

Causes

Dentigerous cysts are small bits of tooth material that have formed where they should not be.

A sac will form around the dental material, lined with a mucous membrane like that found in the sinuses or mouth. The dental material will be formed from birth, but may not be obvious until the cyst becomes infected and starts to drain. This usually happens somewhere around two years of age, but it can happen sooner or not be evident until the horse is older.

Diagnoses

Your veterinarian will determine the type of cyst your horse has, whether it be benign, cancerous or infected. Because the membrane inside the cyst secretes fluids, the cyst may appear pliable, or quite hard. Imaging will confirm the diagnoses and help you and your vet decide what the best treatment option is.  

Treatment

Often, dentigerous cysts can be left without harming the horse. They may look unsightly, and require a bit more care, but are usually not dangerous. If they are causing discomfort or infection is a problem, they can be surgically removed under general anesthetic. The actual dental material that caused the cyst may or may not be found and if there is residual material left behind, another cyst may form. Often, owners opt to leave them alone, unless they are causing a problem. If they become large, they can be drained by your veterinarian. Draining a cyst can provide an entry for infection, so discuss the best strategy with your veterinarian. You may decide that surgery is the route for you and your horse, or you may decide that a less aggressive strategy is the best option.

Prevention

Because the placement of the dental material in places where dental material doesn’t belong happens before a foal is born, there is little that owners can do to prevent this condition.

If your horse develops a dentigerous cyst, keep it clean, especially if there is drainage,  and cover it to keep flies off to ward off infection.

Resources

http://www.merckmanuals.com/vet/digestive_system/congenital_and_inherited_anomalies_of_the_digestive_system/cysts_and_sinuses_of_the_head_and_neck.html