PMC7326087_01
Cat no. 1. (A,B) Histopathology. (A) Cerebral cortex, the leptomeninx (arrows) and neuroparenchyma (black arrowheads) is severely infiltrated with mononuclear inflammatory cells associated with rod-shaped microglial cells (white arrows) in the adjacent neuroparenchyma. HE, bar = 50 mum. (B) Cerebral cortex showing severe vasculitis with mural and perivascular infiltration of lymphocytes (arrows), macrophages (white arrowheads), and plasma cells (black arrowheads). HE, bar = 60 mum.
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F1
Histology revealed a multifocal moderate lympho-histiocytic and plasmacytic meningoencephalomyelitis and vasculitis (Figure 1). Particularly adjacent to affected blood vessels a moderate microgliosis with rod-shaped microglial cells was present in the neuroparenchyma (Figure 1).
Cat no. 2. (A,B) Magnetic resonance imaging (MRI): Midsagittal (A) and transversal section (B) of the brain of cat 2 at the level of the interthalamic adhesion in T2 weighted (T2w) sequences. Note the intramedullary hyperintense lesions of the brainstem and the subcortical white matter as well as the mass lesion with signal void in the myelencephalon. Left side is marked with L. (C-E) Histopathology. (C) Pons, focally severe meningitis (X) with severe hemorrhages in the adjacent neuroparenchyma (arrow) and vacuolization of the white matter as well as spheroids (arrowheads), HE, bar = 100 mum. (D) Hippocampus, severe neuronal necrosis (arrows) and loss. HE, bar = 50 mum. (E) Cerebral cortex with focally severe, perivascular, lympho-histiocytic encephalitis. HE, bar = 60 mum.
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F2
Additionally, a well-demarcated intraaxial lesion in the myelencephalon reaching into the cranial cervical spinal cord displaying mild mass effect with signal void in T2w and GRASE was visible (Figure 2), which was surrounded by a hyperintense area additionally involving the ventral area of the cerebellar vermis. Histopathology of the brain revealed acute focal extensive segmental neuronal necrosis of deep cortical neurons and neurons of the hippocampal CA2 region (Figure 2) associated with mild edema of the adjacent neuropil and hypertrophy of capillary endothelial cells. At the level of the pons a severe, focal, predominantly lymphocytic perivascular meningitis with extensive meningeal hemorrhage extending into the adjacent subpial neuroparenchyma and acute degeneration and necrosis of the white matter (liquefactive necrosis) associated with myelin sheath dilatation, axonal swellings and infiltration of few neutrophils and gitter cells was detected (Figure 2). Additional lesions consisted of multifocal, mild to severe, perivascular lympho-histiocytic meningoencephalitis (Figure 2).
Cat no. 3. (A,B) Magnetic resonance imaging (MRI): Dorsal (A) and transversal section (B) of the brain at the level of the interthalamic adhesion in T1w sequences post-contrast application. Note the small rim of contrast enhancement in the lateral ependymal lining of the right lateral ventricle and the slightly decreased volume of the right lateral ventricle. Left side is marked with L. (C-F) Histopathology. (C) Hippocampus with severe neuronal loss in the CA2 and CA3 regions (arrowheads). HE, bar = 100 mum. (D) Periventricular white matter with severe microgliosis (black arrowheads), infiltration of gitter cells (blue arrowheads) and gemistocytes (arrows). HE, bar = 50 mum. (E) Brain stem, moderate lympho-histiocytic perivascular encephalitis with prominent microgliosis (arrowheads), astrocytosis and presence of gemistocytes (arrows). HE, bar = 60 mum.
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F3
MRI (Table 1) of the brain revealed only a small focal intraaxial lesion with mild mass effect in the ventro-lateral ependymal lining of the right lateral ventricle, isointense in T2w and T1w to normal white matter, hyperintense in fluid attenuated inversion recovery (FLAIR), and with marked homogenous contrast enhancement (Figure 3). Histology revealed a multifocal mild to moderate, perivascular lympho-histiocytic meningoencephalitis particularly in the cerebral cortex and in the brainstem occasionally associated with prominent astro- and microgliosis (Figure 3). Hippocampal CA2 and CA3 sectors showed extensive loss of neurons associated with mild astro- and microgliosis and the periventricular white matter of the parietal and temporal cerebrum was affected by severe partly nodular, partly diffuse microglial and astroglial proliferation with numerous gemistocytes and gitter cells (Figure 3).
PMC7326087_02
Cat no. 4. (A,B) Magnetic resonance imaging (MRI): Midsagittal section of the spinal cord at the thoracolumbar junction in T2w (A) and T1w post-contrast (B) sequences. First lumbar vertebra is marked with L1. Note the intramedullary hyperintense signal (A) from T11 to L1 and the focal contrast enhancement at the level of T12 (B). (C) Histopathology: Thoracic spinal cord showing a focally extensive severe lympho-histiocytic inflammation (X) associated with dilatation of myelin sheaths and swollen axons (arrowheads). In addition, a severe meningeal fibrosis is present (arrows). HE, bar = 100 mum.
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F4
Only a small round well-demarcated intramedullary area at the level of T12 displayed marked homogeneous contrast enhancement (Figure 4). At the level of T11-13 a severe circumferential meningeal fibrosis including all layers extending into the spinal neuroparenchyma was found (Figure 4).