Os epihyoideum
The epihyoid is a small connecting bone in the hyoid apparatus (the chain of bones that supports the tongue and larynx). It sits between the larger stylohyoid and the ceratohyoid. The entire hyoid apparatus is mobile and plays roles in swallowing, vocalization, and tongue movement. In horses it is relevant to temporohyoid osteoarthropathy (THO), a condition in which the temporohyoid joint becomes inflamed or fused, sometimes leading to fracture and neurologic signs.
The hyoid apparatus is assessed by throat palpation and guttural-pouch endoscopy. Temporohyoid osteoarthropathy (THO) is a serious condition; CT is the gold standard for diagnosis. Clinical signs can include head shaking, difficulty eating, facial-nerve deficits, or vestibular signs if fracture occurs.
## Overview This entry indicates a structure or condition that is rarely affected on its own. Clinical signs, when present, are usually part of a larger regional problem rather than an isolated disea
Progressive proliferative osteoarthropathy of the temporohyoid joint that may cause fusion of the joint and fracture of the petrous temporal bone, damaging CN VII and CN VIII as they traverse the bone
## Overview Fracture of the hyoid apparatus (the bony support of the tongue and larynx) is uncommon and usually traumatic. It can cause difficulty swallowing, throatlatch swelling, pain on manipulati
Sudden head shaking, difficulty chewing or swallowing, or asymmetric facial expression warrants veterinary evaluation. Do not force the head or mouth if the horse is in pain.
## Overview This entry indicates a structure or condition that is rarely affected on its own. Clinical signs, when present, are usually part of a larger regional problem rather than an isolated disease. Evaluation focuses on the surrounding anatomy. ## Causes Not applicable as a primary condition. ## Diagnosis Assessment of the broader region. ## Treatment Directed at the primary problem. ## Recovery and Prognosis Depends on the underlying condition. ## Prevention Depends on the primary issue. Signs include: rarely produces independent clinical signs; usually part of a larger regional problem
Progressive proliferative osteoarthropathy of the temporohyoid joint that may cause fusion of the joint and fracture of the petrous temporal bone, damaging CN VII and CN VIII as they traverse the bone. Signs include: Consult veterinarian for specific symptoms.; Head shaking; difficulty eating; ear rubbing; acute onset vestibular signs (head tilt, nystagmus, circling); facial nerve paralysis; keratitis (corneal ulceration from inability to blink)
## Overview Fracture of the hyoid apparatus (the bony support of the tongue and larynx) is uncommon and usually traumatic. It can cause difficulty swallowing, throatlatch swelling, pain on manipulation, abnormal respiratory noise, and sometimes epistaxis. Resistance to poll flexion may be noted. ## Causes Trauma to the throat or tongue region, or excessive traction. ## Diagnosis Radiographs or computed tomography of the hyoid bones, endoscopy, and clinical signs of dysphagia or local pain. ## Treatment Conservative management with soft feeds and anti-inflammatories for stable fractures. Surgical repair is rarely required. Supportive care for dysphagia. ## Recovery and Prognosis Generally good for uncomplicated fractures. Persistent dysphagia worsens the outlook. ## Prevention Avoidance of throat trauma. Signs include: difficulty swallowing; swelling under the jaw or throat; pain on throat manipulation; abnormal respiratory noise; possible epistaxis
The hyoid apparatus is assessed by throat palpation and guttural-pouch endoscopy. Temporohyoid osteoarthropathy (THO) is a serious condition; CT is the gold standard for diagnosis. Clinical signs can include head shaking, difficulty eating, facial-nerve deficits, or vestibular signs if fracture occurs.
Sudden head shaking, difficulty chewing or swallowing, or asymmetric facial expression warrants veterinary evaluation. Do not force the head or mouth if the horse is in pain.
See the Epihyoid Bone (Right) on our interactive 3D horse model. Open 3D Model