PMC6448120_01
(a) Image of an 8-year-old tortoiseshell spayed female domestic shorthair cat on initial presentation with open bite. (b) Rostral aspect of the oral cavity under general anaesthesia. Note the bilateral submucosal haematomas involving the retromolar areas (white arrows). The vertical mandibular range of motion (vmROM) was 22 mm
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Oral examination showed painful mouth opening with a restricted vertical mandibular range of motion (vmROM), and an inability to close the mouth (Figure 1).
CT of the head. Transverse reconstructions at the level of both rami. (a) Irregular periosteal new bone on both mandibulae and parietal bones (white arrows); dystrophic mineralisation in temporalis/pterygoid muscles (black arrows). (b,c) Bilateral, non-enhancing, ill-defined hypodense areas in temporalis and medial pterygoid muscles (white arrowheads)
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Selected reconstructed images are provided (Figure 2).
Photomicrograph of a section of the needle-core biopsy of the right temporalis muscle. (a) Extensive replacement of the muscle (asterisks) by a dense mesenchymal tissue exhibiting progressive ossification (arrows). Haematoxylin and eosin, bar = 250 microm. (b) Proliferation of fibroblasts (white arrows) and osteoblasts (black arrow) gradually forming trabeculae of mineralised lamellar bone. Note residual atrophic muscle fibres embedded in the lesion (black arrowheads). Haematoxylin and eosin, bar = 100 microm
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The mesenchymal tissue was composed of peripheral fascicles of activated fibroblasts and intermediate osteoblasts depositing woven bone and gradually forming trabeculae of lamellar bone (Figure 3).