Diagnosis and treatment of dynamic closed-mouth jaw locking in a dog.

CASE DESCRIPTION: A 5-year-old neutered male English Bulldog was evaluated for intermittent closed-mouth jaw locking of approximately 1 week's duration. CLINICAL FINDINGS: Initial physical examination revealed a nonpainful inability to open the jaw with and without manual assistance; however, manipulation of the jaw after the dog was sedated for diagnostic imaging restored jaw function. Anesthesia was subsequently induced, and computed tomography was performed with the jaw open and closed; contrast agent-enhanced images of the closed jaw were also obtained. No abnormalities of the temporomandibular joints or retrobulbar space were detected. Fluoroscopic examination of movement of the temporomandibular joints revealed a dynamic interference of the rostrodorsal aspect of the coronoid process of the left mandibular ramus with the medial surface of the frontal process of the left zygomatic bone or the left orbital ligament. TREATMENT AND OUTCOME: Partial excision of the coronoid process of the left mandibular ramus was performed. The dog recovered without complication and was able to open and close its jaw and eat within 6 hours after surgery. No additional episodes of jaw locking were detected during the 6 months after surgery. CLINICAL RELEVANCE: To the authors' knowledge, closed-mouth jaw locking in animals attributable to dynamic interference of the rostrodorsal aspect of the coronoid process of a mandibular ramus with the medial surface of the frontal process of a zygomatic bone or an orbital ligament has not been described. Surgical excision of the coronoid process of the mandibular ramus appeared to provide a successful outcome in the dog of this report.

Locked jaw syndrome in dogs and cats: 37 cases (1998-2005).

A consecutive series of cases of dogs and cats with locked jaw syndrome (inability to open or close the mouth) are reported in this study. Dogs were significantly overrepresented (84.0%) and adult dogs were more frequently affected (81.0%). Temporomandibular joint ankylosis due to fracture was the most common cause (54.0%) of locked jaw syndrome. Additional potential causes of locked jaw syndrome are masticatory muscle myositis, neoplasia, trigeminal nerve paralysis and central neurological lesions, temporomandibular joint luxation and dysplasia, osteoarthritis, retrobulbar abscess, tetanus, and severe ear disease. Treatment of locked jaw is directed towards the primary cause. It is important to treat the tonic spasm in order to minimize periarticular fibrosis. Surgical intervention is recommended for temporomandibular joint ankylosis. Masticatory muscle myositis treatment is initiated by gradually opening the mouth, with medical treatment based on immunosuppressive therapy. Fracture and masticatory muscle myositis are associated with a relatively good prognosis in regard to short-term outcome as compared to animals with central neurologic lesions or osteosarcoma which have a poor prognosis.

Intermittent open-mouth lower jaw locking in five dogs.

Intermittent open-mouth lower jaw locking was documented in 5 dogs. In contrast to what has been reported in other cases, pronounced radiographic abnormalities in the temporomandibular joints were not observed. In 4 of the dogs, locking episodes started at a later age (35 to 83.5 months) than had been reported by others (6 to 22 months). Duration and frequency of locking were variable. Lateral shifting of the jaw and lack of neurologic deficits indicated a temporomandibular joint abnormality. Excision of the rostroventral portion of the involved zygomatic arch prevented locking in all cases. This syndrome involves variable severity of temporomandibular joint dysplasia, which could account for the variable age of onset and random frequency of locking episodes.