Page 257 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

232 CHAPTER 1

VetBooks.ir 1.438 1.439

Fig. 1.439 Ultrasonogram of a mature suture
periosteitis.

1.440

Fig. 1.438 Lateral radiograph of the head of a horse
showing the osseous changes associated with a mature
suture periosteitis.

DISEASE OF THE TEMPOROHYOID TB
ARTICULATION

Definition/overview TH
The temporohyoid articulation is a short cartilagi-
nous region between the proximal extremity of the Fig. 1.440 Dissection to show the tympanohyoid
stylohyoid bone and the petrous temporal bone, articulation (arrow) in a neonatal foal.
which lies immediately ventrolateral to the middle TH = tympanohyoid bone; TB = tympanic bulla.
ear region (Fig. 1.440). Functionally, it is slightly
flexible and thus dampens the movements of the
hyoid apparatus during routine tongue motion. neurological signs. The resulting inflammation and
possible new bone formation can also lead to dam-
Aetiology/pathophysiology age of the glossopharyngeal and vagus nerves (CNs
Disease of the middle ear can result in ossification IX and X, respectively), causing additional neuro-
of the cartilaginous temporohyoid articulation, logical signs. Fracture of the adjacent stylohyoid
but cases may present without any history of ear bone can be associated with acute onset of CN VII
disease. Extension of infection from the middle and VIII deficits.
ear to the temporohyoid articulation is thought
to reduce the flexibility of this region, and nor- Clinical presentation
mal tongue movements may then result in fracture Affected horses may present with a range of signs
of the petrous part of the temporal bone. Due to indicating neurological dysfunction, including head
their close proximity, the facial and vestibuloco- tilt, facial nerve paralysis, keratitis, nystagmus and
chlear nerves (CNs VII and VIII, respectively) ataxia. Head shaking or aural discharge may also be
can be affected and their dysfunction can cause observed.