PMC4672276_01
(A) Transverse T2-weighted turbo spin echo MR image of a 1-year-old spayed female Shih Tzu presenting for episodic multifocal encephalopathy. There are bilaterally symmetric, teardrop-shaped hyperintensities of the caudate nuclei suggestive of a metabolic encephalopathy. (B) Transverse FLAIR MR image at the same level as in (A) reveals the caudate nuclear lesions are hypointense with hyperintense rims. This suggests a low-protein cavitated lesion within the caudate nuclei surrounded by either edema, proteinaceous fluid, inflammation, or, less likely, neoplastic tissue. (C) Formalin fixed brain, dog. Photograph of a transverse section of the cerebrum at the level of the caudate nuclei. There are bilateral, linear cavitated foci of necrosis within the caudate nuclei adjacent to the internal capsule; bar = 5 mm. (D) Brain, dog. Photomicrograph at the same level as (C). Bilateral, linear, cavitated foci of necrosis are present adjacent to the internal capsule. H&E stain; Subgross Image, bar = 1.5 mm.
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F1
Cervical and brain MRI performed with a 1.5-T unit3 revealed non-contrast-enhancing bilaterally symmetric, teardrop-shaped T2-hyperintensities of the caudate nuclei that were hypointense with hyperintense periphery on FLAIR and hypointense to gray matter on T1-weighted images (Figures 1A,B). On post-mortem examination, gross abnormalities included bilateral cavitated foci within the caudate nuclei (Figure 1C), pallor of several focal skeletal muscle bundles, dorsal and pelvic limb muscle wasting, multifocal to coalescing hepatic parenchymal pallor, and congestion of multiple organs. Histopathological examination of the brain identified severe, bilateral focal necrosis of the caudate nuclei with cavitation, Gitter cell infiltration, rare axonal swelling (spheroids), regional rarefaction and gliosis (Figure 1D).
(A) Transverse T2-weighed turbo spin echo MR image at the level of the cerebellar nuclei. There are subtle, bilaterally symmetric hyperintensities of the cerebellar nuclei (white arrow) that correspond to areas of vacuolation on histopathology. (B) Brain, dog. Subgross photomicrograph of the cerebellum and medulla. Multifocal regions of pallor are present at the level of the lateral, interposital, and fastigial nuclei (white arrows), corresponding with the MRI. H&E stain. (C) Brain, dog. High magnification photomicrograph of the cerebellum within a pale region denoted by the arrows in (B). Note the myelin vacuolation (white arrows) and axonal swelling (spheroid, black arrow). There are increased numbers of glial cells in this region, including microglia and astroglia, which are multifocally undergoing cytoplasmic swelling. H&E stain; 400 x magnification; bar = 20 mum.
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F2
Non-contrast enhancing, bilaterally symmetric, subtle T2-hyperintensities of the cerebellar nuclei that remained hyperintense on FLAIR and isointense to gray matter on T1-weighted images were also identified (Figure 2A). In the cerebellum, neuropil vacuolation was present at the level of the lateral, interposital, and fastigial nuclei, accompanied by gliosis, glial cytoplasmic swelling, and axonal spheroid formation (Figures 2B,C).
Photomicrograph of cryosections of the triceps muscle stained with oil red O stain reveals the presence of numerous intramyofiber lipid droplets, consistent with a lipid storage myopathy. Oil red O stain; bar = 50 mum.
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F3
The most striking abnormality was the presence of numerous vacuoles within most myofibers containing excessive and variably sized intramyofiber lipid droplets utilizing the oil red O stain for neutral triglycerides (Figure 3).