Nessler J, Wohlsein P, Junginger J, Hansmann F, Erath J, Söbbeler F, et al. Meningoencephalomyelitis of Unknown Origin in Cats: A Case Series Describing Clinical and Pathological Findings. Front Vet Sci. 2020.
Meningoencephalomyelitis of unknown origin (MUO) refers to any one of a group of immune mediated inflammatory neurologic conditions. These non-infectious diseases lead to inflammation of the brain and a variety of neurologic signs. While these are relatively common conditions in dogs, they are much less frequently diagnosed in cats. This family of diseases can only be definitively diagnosed on biopsy of the brain. As this is rarely practical, often times a working diagnosis is attained based on MRI and cerebral spinal fluid (CSF) findings. There is little data in the literature on this condition in cats, especially looking at both clinical and pathologic findings.
The purpose of this case series was to describe the clinical and histopathological findings in a group of cats diagnosed with MUO. It was designed as a retrospective case series based on a single referral center. Cases from 2012-2019 were reviewed to find cats who received a neurology consultation, MRI and/or CSF tap, and necropsy. Necropsy results needed to be confirmatory of MUO. There were no exclusion criteria defined.
Of 207 cats with either an MRI or CSF tap, 38 cats had a suspected MUO, in 11 cats MUO was presumed, and in 4 cats it was confirmed with necropsy. The median age of these cats was 7 years, which is older than cats with infectious encephalitis (1-4.88 years).
In addition to neurologic signs, ¾ cats had systemic evidence of inflammation including fever, weight loss, elevated white cells, and decreased appetite. These extra-neurologic signs appear more common in cats than similarly affected dogs. MRI of cats with MUO showed multifocal intraparenchymal lesions in the CNS with contrast enhancement.
CSF changes were fairly minor, with albuminocytologic dissociation most commonly seen but results often normal. This was contrasted with patients with infectious encephalitis who often had very active CSF samples.
In three of the necropsied cats, histopathology revealed a multifocal, lympho-histiocytic meningoencephalitis. The final case was diagnosed as lympho-histiocytic myelitis.
This paper has obvious limitations, as a fairly small case series. However, it provides a framework for the understanding, diagnosis, and treatment options for cats with this uncommon condition. Further work is needed in larger numbers of cats, especially focused on treatment options and long-term prognoses. (MRK)