Abstract
Background: Listeria rhombencephalitis, infection of the brainstem with Listeria monocytogenes, occurs mainly in humans and farmed ruminants and is associated with high fatality rates. Small ruminants (goats and sheep) are a large animal model due to neuropathological similarities. The purpose of this study was to define magnetic resonance imaging (MRI) features of listeria rhombencephalitis in naturally infected small ruminants and correlate them with histopathology. Secondly, the purpose of this study was to compare the results with MRI findings reported in humans.Methods: Twenty small ruminants (13 sheep and 7 goats) with listeria rhombencephalitis were prospectively enrolled and underwent in vivo MRI of the brain, including T2-weighted, fluid attenuation inversion recovery, and T1-weighted sequences pre- and post-contrast administration and postmortem histopathology. In MRI, lesions were characterized by location, extent, border definition, signal intensity, and contrast enhancement. In histopathology, the location, cell type, severity, and chronicity of inflammatory infiltrates and signs of vascular damage were recorded. In addition, histopathologic slides were matched to MRIs, and histopathologic and MRI features were compared.Results: Asymmetric T2-hyperintense lesions in the brainstem were observed in all animals and corresponded to the location and pattern of inflammatory infiltrates in histopathology. Contrast enhancement in the brainstem was observed in 10 animals and was associated with vessel wall damage and perivascular fibrin accumulation in 8 of 10 animals. MRI underestimated the extension into rostral brain parts and the involvement of trigeminal ganglia and meninges.Conclusion: Asymmetric T2-hyperintense lesions in the brainstem with or without contrast enhancement can be established as criteria for the diagnosis of listeria rhombencephalitis in small ruminants. Brainstem lesions were similar to human listeria rhombencephalitis in terms of signal intensity and location. Different from humans, contrast enhancement was a rare finding, and abscessation was not observed.
Highlights
Listeriosis is an important foodborne infection with the facultative intracellular bacterium Listeria monocytogenes (LM) occurring mainly in humans and farmed ruminants [1, 2]
Twenty animals (13 sheep and 7 goats) were enrolled after confirmation of neurolisteriosis based on histopathological examination and detection of LM by bacteriological culture and/or immunohistochemistry of brain tissue
If we evaluate the suitability of small ruminants as an animal model from the imaging standpoint, we should appreciate that small ruminants suffer from the rhombencephalitis type of neurolisteriosis and not the meningoencephalitis type
Summary
Listeriosis is an important foodborne infection with the facultative intracellular bacterium Listeria monocytogenes (LM) occurring mainly in humans and farmed ruminants [1, 2]. Neurolisteriosis generally develops as diffuse meningitis or meningoencephalitis, whereas between 1 and 24% of patients suffer from brainstem involvement or rhombencephalitis [5,6,7,8,9,10]. Rhombencephalitis is a term interchangeably used with brainstem encephalitis and defined as the isolated infection of the brainstem and optionally the cerebellum. It was first described in humans by Eck in 1957 [11]. Infection of the brainstem with Listeria monocytogenes, occurs mainly in humans and farmed ruminants and is associated with high fatality rates. The purpose of this study was to define magnetic resonance imaging (MRI) features of listeria rhombencephalitis in naturally infected small ruminants and correlate them with histopathology. The purpose of this study was to compare the results with MRI findings reported in humans
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