PMC9516294_01
Computed tomography pre-contrast (A) and post-contrast (B) images of the head of a 5-month old Cavalier King Charles Spaniel affected by masticatory muscle myositis. Note the severe, diffuse, and bilateral atrophy of temporalis, masseter, and pterygoid muscles and contrast enhancement of the masticatory muscle in post-contrast image (* temporalis muscle, #masseter muscle, pterygoid muscle, ||digastricus muscle).
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F1
Milan, Italy) of the head highlighted symmetrical reduction in volume of masseter, temporalis, and pterygoid muscles with moderate contrast enhancement (Figure 1); mandibular and retropharyngeal lymphadenomegaly was also reported. Magnetic resonance imaging study (1.5
Magnetic resonance imaging study of the head of a 5-month old Cavalier King Charles Spaniel affected by masticatory muscle myositis; pre-contrast T1-W image (A), post-contrast T1-W image (B), fluid attenuated inversion recovery (FLAIR) (C) and short tau inversion recovery (STIR) (D) images. Note the severe, diffuse, and bilateral atrophy of temporalis, masseter, and pterygoid muscles that appear isointense on T1-W images pre-contrast (A) and showing a strong contrast enhancement (B); these muscles appear hyperintense on FLAIR (C) and STIR (D) images, compared to the signal in normal muscles (* temporalis muscle, #masseter muscle, pterygoid muscle, ||digastricus muscle).
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Tesla, SIGNA Creator, General Electric, Milan, Italy) of the head revealed symmetric and severe masticatory muscle atrophy. Temporalis, masseter, and pterygoid muscles showed diffuse, bilateral and heterogeneous hyperintensity on T2-weighted, fluid attenuated inversion recovery (FLAIR) and short tau inversion recovery (STIR) images; these muscles appeared isointense on T1-weighted sequences compared to the signal of normal muscles (Figure 2). A strong and diffuse contrast enhancement of the masticatory muscle (with the exception of the digastricus muscle) was present after contrast administration (Figure 2), no signal changes, contrast enhancement or swelling of extraocular muscle were identified (Figure 3); regional lymph nodes appeared enlarged.
Magnetic resonance imaging study of the head of a 5-month old Cavalier King Charles Spaniel affected by masticatory muscle myositis; pre-contrast T1-W image (A), post-contrast T1-W subtraction image (B), pre contrast 3D T1-W image (C). Note the absence of extraocular muscle swelling and contrast enhancement; no evidence of exophthalmos.
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A strong and diffuse contrast enhancement of the masticatory muscle (with the exception of the digastricus muscle) was present after contrast administration (Figure 2), no signal changes, contrast enhancement or swelling of extraocular muscle were identified (Figure 3); regional lymph nodes appeared enlarged.
Photomicrograph of histological, hematoxylin and eosin stained, section of a temporalis muscle of a 5-month old Cavalier King Charles Spaniel affected by masticatory muscle myositis. Note the inflammatory infiltration and the interstitial and nodular fibrosis of the temporalis muscle.
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Temporalis and masseter muscle histopathology revealed multifocal, mixed cellular, chronic, moderate to marked myofascitis with myofibrosis and muscle atrophy (Figure 4).