Related Experiment Video
Updated: Aug 29, 2025
Flow Cytometric Analysis of Lymphocyte Infiltration in Central Nervous System during Experimental Autoimmune Encephalomyelitis
Published on: November 17, 2020
Case report: Lympho-histiocytic meningoencephalitis with central nervous system vasculitis of unknown origin in three
Isabel Zdora1,2, Jonathan Raue3, Franz Söbbeler3
1Department of Pathology, University of Veterinary Medicine Hannover, Hannover, Germany.
Abstract:
Meningoencephalitis of unknown origin (MUO) is an umbrella term for a variety of subtypes of meningoencephalitis of dogs and cats with no identifiable infectious agent. In dogs, granulomatous meningoencephalitis (GME), necrotizing meningoencephalitis (NME), and necrotizing leukoencephalitis (NLE) are the most commonly reported subtypes. However, sporadically there are reports about other subtypes such as greyhound encephalitis or eosinophilic meningoencephalitis. The following case series presents three dogs with peracute to acute progressive signs of encephalopathy. The magnetic resonance imaging (MRI) of two dogs (post mortem n = 1/2) showed severe, diffuse swelling of the cortical gray matter with increased signal intensity in T2weighted (w) and fluid-attenuated inversion recovery (FLAIR) and decreased signal intensity in T1w. Additionally, focal to multifocal areas with signal void in both dogs and caudal transforaminal herniation of the cerebellum in one dog was observed. Post mortem histopathological examination revealed lympho-histiocytic encephalitis and central nervous system (CNS) vasculitis in all dogs. No infectious agents were detectable by histopathology (hematoxylin and eosin stain), periodic acid-Schiff reaction (PAS), Ziehl-Neelsen stain and immunohistochemistry for Canine adenovirus-1, Parvovirus, Listeria monocytogenes, Parainfluenzavirus, Toxoplasma gondii, Herpes-suis virus, Pan-Morbillivirus, Tick born encephalitis virus, Severe acute respiratory syndrome coronavirus (SARS-CoV) 2. Furthermore, two dogs were tested negative for rabies virus. To the best of the authors' knowledge, this is the first report of a lympho-histiocytic encephalitis with CNS vasculitis with no identifiable infectious agent. It is suggested to consider this as an additional subtype of MUO with severe clinical signs.
Insights
This study describes a new subtype of meningoencephalitis of unknown origin (MUO) in dogs, characterized by lympho-histiocytic encephalitis and central nervous system vasculitis without an identifiable infectious agent.
Area of Science:
- Veterinary Neurology
- Immunology
- Pathology
Background:
- Meningoencephalitis of unknown origin (MUO) encompasses various inflammatory brain diseases in pets lacking a specific cause.
- Common MUO subtypes in dogs include granulomatous meningoencephalitis (GME), necrotizing meningoencephalitis (NME), and necrotizing leukoencephalitis (NLE).
Observation:
- A case series of three dogs presented with acute, severe encephalopathy.
- Magnetic resonance imaging (MRI) revealed diffuse cerebral swelling, altered signal intensities, and cerebellar herniation in affected dogs.
- Histopathological examination identified lympho-histiocytic encephalitis and central nervous system (CNS) vasculitis.
Findings:
- Extensive diagnostic testing, including histopathology and immunohistochemistry, failed to detect any infectious agents.
- No evidence of common canine viruses, bacteria, or protozoa was found.
- Rabies virus testing was also negative in two of the dogs.
Implications:
- This report suggests a novel subtype of MUO characterized by lympho-histiocytic encephalitis and CNS vasculitis.
- This newly identified condition presents with severe clinical signs and warrants consideration in the differential diagnosis of canine encephalopathies.
- Further research is needed to elucidate the pathogenesis and specific triggers of this emerging MUO subtype.
