Page 86 - Atlas of Small Animal CT and MRI

76 Atlas of Small Animal CT and MRI

Figure 1.5.9 Extraocular Myositis (Canine) MR

(a) T1, DP (b) T2, DP (c) T1+C+FS, DP

(d) T1, TP (e) T2, TP (f) T1+C+FS, TP

(g) T1, TP (h) PD, TP (i) T1+C+FS, TP
1y MC Labrador Retriever with bilateral blepharospasm and reduced response to retropulsion. Images d–e are at the level of the globe and
images g–i are further caudal within the retrobulbar space. There is an increase in volume and loss of definition of the extraocular muscles
(a–c,g–i). This is associated with an increase in extraocular muscle signal intensity on T2 images (b,h). There is diffuse contrast enhance-
ment of the extraaxial muscles (c,i) and ocular adnexa (f), bilaterally. Focal meningeal enhancement is also present in the frontal lobar
region bilaterally (c: arrowheads) and may represent an extension of the inflammatory response through the optic canal or orbital fissure.
Extraocular muscle biopsy revealed chronic lymphohistiocytic myositis and myocyte atrophy, which is consistent with the microscopic
description reported for extraocular myositis. Conjunctival biopsy revealed marked subacute fibrinosuppurative conjunctivitis.

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