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Use of three-dimensional computed tomography for diagnosis and treatment planning for open-mouth jaw locking in a cat

Rebekah C. Beam DVM1, David A. Kunz DVM2, Cristi R. Cook DVM, MS, DACVR3, Robert L. Carson DVM4, Phillip Briscoe DVM5, and James L. Cook DVM, PhD, DACVS6
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  • 1 Comparative Orthopaedic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211
  • | 2 Department of Veterinary Medicine and Surgery, Veterinary Medical Teaching Hospital, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211
  • | 3 Comparative Orthopaedic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211
  • | 4 General Veterinary Clinic, 3740 Highway MM, Hannibal, MO 63401
  • | 5 General Veterinary Clinic, 3740 Highway MM, Hannibal, MO 63401
  • | 6 Comparative Orthopaedic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211

Abstract

Case Description—A 2.5-year-old spayed female Persian cat was evaluated for acute inability to close its mouth.

Clinical Findings—A wry-mouth malocclusion was evident, and the right side of the mandible was longer than the left side. The right mandibular tooth row appeared to be lowered. The lower jaw was persistently maintained in an open position. The presumptive diagnosis was open-mouth jaw locking. Diagnostic imaging with computed tomography and 3-dimensional reconstruction was performed for definitive diagnosis and to achieve a better understanding of the lesions. Imaging revealed locking of the right ramus of the mandible, which was displaced ventrolaterally, causing the coronoid process to impinge on the right zygomatic arch.

Treatment and Outcome—A bilateral partial ostectomy of the rostroventral margins of the zygomatic arches with an autogenous fat graft implantation was performed. The cat recovered without complications and by the following morning was bright, alert, and responsive and eating canned cat food comfortably. One year after surgery, the owner reported that the cat had continued to function well, was eating normally, and had not had any observed locking episodes since surgery.

Clinical Relevance—Unlike radiographic imaging, computed tomography may be used to create 3-dimensional reconstructions of structures in cases of suspected open-mouth jaw locking; improve evaluation of the lesions; and improve decision-making and client education for diagnosis, treatment options, and prognosis.

Abstract

Case Description—A 2.5-year-old spayed female Persian cat was evaluated for acute inability to close its mouth.

Clinical Findings—A wry-mouth malocclusion was evident, and the right side of the mandible was longer than the left side. The right mandibular tooth row appeared to be lowered. The lower jaw was persistently maintained in an open position. The presumptive diagnosis was open-mouth jaw locking. Diagnostic imaging with computed tomography and 3-dimensional reconstruction was performed for definitive diagnosis and to achieve a better understanding of the lesions. Imaging revealed locking of the right ramus of the mandible, which was displaced ventrolaterally, causing the coronoid process to impinge on the right zygomatic arch.

Treatment and Outcome—A bilateral partial ostectomy of the rostroventral margins of the zygomatic arches with an autogenous fat graft implantation was performed. The cat recovered without complications and by the following morning was bright, alert, and responsive and eating canned cat food comfortably. One year after surgery, the owner reported that the cat had continued to function well, was eating normally, and had not had any observed locking episodes since surgery.

Clinical Relevance—Unlike radiographic imaging, computed tomography may be used to create 3-dimensional reconstructions of structures in cases of suspected open-mouth jaw locking; improve evaluation of the lesions; and improve decision-making and client education for diagnosis, treatment options, and prognosis.

Contributor Notes

Dr. Beam's present address is Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824.

Address correspondence to Dr. James L. Cook.