Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

630 Small Animal Radiolo g y and Ultrasono graphy
A
B
Fig. 5-23 A, A 5-year-old neutered male domestic short-haired cat was hit by a car. The cat’s
mandibular symphyseal fracture has been repaired with a wire suture but the mandibles did not open
smoothly. The dorsoventral view reveals a normal temporomandibular articulation on the right (long
arrows). There is a subtle misalignment of the left temporomandibular joint with the articular
process of the mandible displaced medially (short arrows). B, Close-up view of A. Diagnosis: Left
temporomandibular joint subluxation.
trauma. In these instances, pathologic fracture secondary to periapical abscesses, hyperparathyroidism,
or tumor may be present. The presence of bony proliferation or lysis at the
site of an acute fracture suggests that the fracture is pathologic.
U LT R A S O N O G R A P H I C E VA LUAT I O N O F H E A D T R AU M A
Ultrasonography may be used to evaluate the integrity of the brain when a skull fracture
has produced a bony defect. The fracture fragment may be evident as a hyperechoic structure
with distant shadowing. Intracranial hemorrhage may produce hypoechoic or hyperechoic
areas within the brain depending on the duration of the hemorrhage. Brain abscess
may develop secondary to trauma, and this may be recognized as a hypoechoic, poorly
defined lesion within the brain (Fig. 5-26). Because abscesses and hematomas have similar
appearances, a fine-needle aspirate would be required to make a definitive diagnosis.
O S T E OA RT H R I T I S
Degenerative joint disease of the temporomandibular joints is seen occasionally. It may occur
as a normal aging change or may be secondary to previous fracture or subluxation. With temporomandibular
degenerative joint disease, the subchondral bone will appear irregular, periarticular
osteophytes may be present, and the joint space appears narrowed (Fig. 5-27).
M I S C E L L A N E O U S D I S E A S E S
Otitis Externa and Otitis Media. The external ear canals are common sites of infection.
The normal air-filled external ear canal may be obliterated due to soft-tissue proliferation
or exudate within the ear canal. Dystrophic calcification of the external ear canals may