Bilateral extracapsular soft-tissue ossification affecting range of TMJ motion in an Airedale terrier

A 3 mo old female Airedale terrier presented with decreased range of motion of the temporomandibular joint (TMJ), which was first recognized at weaning. Computed tomography (CT) revealed abnormal, bilateral ossification of the soft tissues extending from the region of the tympanic bullae to the medial aspect of the angular process of each mandible. Those ossified structures most closely approximated the location of the lateral pterygoid muscles. The ossified structures were present at presentation and initially manifested as complete ossification on the right side. The condition progressed to complete bilateral ossification by 3 yr of age. The mandibular condyles associated with the temporomandibular joints were malformed. The patient had severe mandibular distoclusion with deviation of the mandible to the left. The left mandibular cheek teeth were positioned in a caudal cross bite. A single treatment of manual stretching and breakdown of the ossified muscle of mastication by placement of tongue depressors within the oral cavity resulted in no increase in TMJ range of motion as measured by the incisal opening. This is the first reported case of spontaneous false ankylosis of the TMJ in an Airedale terrier.