PMC5954326_01
(a) Images of a 1-year-old mixed breed cat at the time of initial evaluation showing the long thick hair on the head and inability of the observer to appreciate the severe masticatory muscle atrophy. (b) Maximum vertical mandibular range of motion was measured as 12 mm
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Owing to the long haircoat palpation was necessary to appreciate the severe bilaterally symmetrical atrophy of the masticatory musculature (Figure 1a). An intraoral examination was impossible owing to the decreased vertical mandibular range of motion (vmROM) of 11-12 mm as measured with a metric ruler between the upper and lower incisor tips (Figure 1b).
Post-mortem axial CT demonstrating severe bilateral atrophy of the temporalis muscles (white arrows)
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It revealed pronounced bilaterally symmetrical atrophy of the masticatory muscles with no radiographic abnormalities of the temporomandibular joints or other bony structures that would restrict mouth opening (Figure 2).
Histopathologic features, hematoxylin and eosin staining on the temporalis muscle of the cat in Figures 1 and 2 showing marked myofiber loss and fibrosis. Remaining myofibers are atrophic (arrows). A large cluster of mononuclear cells are present in the lower left corner (asterisk). Bar = 50 microm
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All of the temporalis and masseter muscles exhibited similar pathological changes (Figure 3).