Open-mouth jaw locking in cats: a literature review and use of CT in three cases

Abstract

Open-mouth jaw locking has been reported in cats of a wide range of ages, from 1-10 years. Cats with all skull types (brachycephalic, mesaticephalic and dolichocephalic) may be affected, but brachycephalic breeds seem to be over-represented. A CT scan with the jaw locked in place is recommended for diagnosis and surgical planning purposes; two of the cases reported here document the first cases of TMJ dysplasia in cats to be definitively diagnosed using CT. Trauma and symphyseal or TMJ laxity may also predispose to development of the condition. Partial coronoidectomy and partial zygomatic arch resection performed alone or in combination are generally successful at preventing recurrence. Bilateral partial zygomectomy with bilateral partial coronoidectomy has not previously been reported as a surgical treatment, and is recommended when open-mouth jaw locking occurs bilaterally.

Feline skull injuries: Treatment goals and recommended approaches

“…2,10,13,14,17 Locking-jaw syndrome Locking-jaw syndrome is caused by impingement of the dorsal edge of the coronoid process, which moves laterally, on the zygomatic arch ( Figure 21), preventing closure of the mouth. 26 This occurs after maximal opening of the jaw (eg, during yawning, grooming or vocalisation). A breed predisposition to this condition is seen in Persian cats.…”

“…Typically, the malpositioned coronoid process can be palpated laterally to the zygomatic arch and the mouth cannot be closed manually. 11,26 Radiography is the imaging modality commonly used in the investigation of openmouth jaw locking. However, CT scanning is superior to radiography for assessment of the TMJ and to rule out other potential underlying causes, and makes the initial diagnosis of jaw locking easier.…”

“…However, CT scanning is superior to radiography for assessment of the TMJ and to rule out other potential underlying causes, and makes the initial diagnosis of jaw locking easier. 26 There are two main approaches for the management of these patients -closed reduction and surgical treatment. ✜ Closed reduction Under sedation or general anaesthesia, the mouth is opened further, and medial pressure is applied over the coronoid process to achieve reduction.…”

Feline skull injuries: treatment goals and recommended approaches

“…16 ✜ Temporomandibular joint fractures and disorders Locking-jaw syndrome in cats has been described in the literature, and reported to be over-represented in cats with brachycephalic conformation of the skull. 2 It has frequently been associated with temporomandibular joint dysplasia, but it has also been linked to traumatically induced conformational changes of the mandible and zygomatic arch 2,18,19 or even muscular pathology. 18,19 Although other surgical approaches might be applied, the use of rongeurs for partial removal of the zygomatic arch is reported in the literature as an option for this purpose.…”

“…2 It has frequently been associated with temporomandibular joint dysplasia, but it has also been linked to traumatically induced conformational changes of the mandible and zygomatic arch 2,18,19 or even muscular pathology. 18,19 Although other surgical approaches might be applied, the use of rongeurs for partial removal of the zygomatic arch is reported in the literature as an option for this purpose. 2 Additionally, our colleagues mentioned that the bi-gnathic encircling and retaining device (BEARD) technique is extensively explained in our manuscript but is not commonly used in practice.…”