Meningoencephalomyelitis of Unknown Origin in Cats: A Case Series Describing Clinical and Pathological Findings

Abstract

Meningoencephalomyelitis of unknown origin (MUO) is an umbrella term describing inflammatory changes of the central nervous system (CNS) with suspected non-infectious etiology. Diagnosis of MUO mostly remains presumed in a clinical setting. Histopathological and immunohistochemical examination of CNS tissue represent additional tools for detection of inflammation and the exclusion of specific infectious agents. While MUO is well-described in canine patients, only little is known about MUO in cats. Previous reports of feline MUO involve either clinical findings or histopathological examination but not both. The present case series is the first report describing both clinical and histopathological findings of feline MUO: Four cats (age: 1.7–17.8 years) showed acute to chronic progressive neurological signs of encephalopathy or myelopathy. Three cats had extraneural signs (hyperthermia, weight loss, hyporexia, leukocytosis). Magnetic resonance imaging (MRI) showed multifocal intraparenchymal lesions in forebrain, brainstem or spinal cord with homogenous contrast enhancement (2/2). Cerebrospinal fluid (CSF) examination was normal or displayed albuminocytologic dissociation. Histopathology revealed a multifocal, lympho-histiocytic meningoencephalitis in three cases and a lympho-histiocytic myelitis in one case. Immunohistochemistry for feline parvovirus, feline coronavirus, feline herpesvirus, tick borne encephalitis virus, Borna disease virus, morbillivirus, rabies virus, suid herpesvirus-1, and Toxoplasma gondii were negative in all cases. One Sentence Summary This case series is the first one reporting both clinical and histopathological findings in cats with MUO. Feline MUO incorporates heterogeneous subtypes of sterile CNS inflammation.

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“…It has been described first in the 1970s in the Swedish Lake Mälaren region between Stockholm and Uppsala 7 , which remains a hotspot of ‘staggering disease’ to the present. Neurologic disorders possessing striking similarity with this disease entity have been described also in domestic cats in other European countries, particularly in Austria 6, 8, 9, 10, 11 , and even in other felids 12, 13 .…”

“…In addition, fever, behavioural changes such as abnormal vocalization or affectionate behaviour, hypersalivation, depression, hyperaesthesia in dorsal back and lumbar/tail region, reduced spinal reflexes and postural reactions, affection of cranial nerves and opisthotonus were reported in some of the cases. In one animal, generalized seizures were specifically recorded ( Supplemental Table S4 ) 6, 8 . Duration from the reported disease onset to euthanasia ranged from one week to more than one year, with most of the cats being euthanized within less than two months (median two weeks) ( Supplemental Figure S5c; Supplemental Table S3 ).…”

“…In addition, frozen brain samples from 21 cats originating from Sweden, Austria, and Germany without encephalitis were included as controls. An additional control group was composed of eight cats from Germany that had suffered from encephalitis of other types or causes, such as CNS manifestation of feline coronavirus (FCoV)-associated feline infectious peritonitis (FIP), vasculitic disorders and immune-mediated limbic encephalitis ( Table 1 ) 6 . Metadata were provided by the submitters and/or extracted from the previous publications, including course and duration of disease, age, sex, origin, and outdoor access of the cats ( Supplemental Table S3 ), as well as clinical signs ( Supplemental Table S4 ).…”

“…The samples dated back to 1991 to 1993 (Austria) or 2017 to 2022 (Germany and Sweden). Some of these cases were published previously 6,8,11 . In addition, frozen brain samples from 21 cats originating from Sweden, Austria, and Germany without encephalitis were included as controls.…”

“…The latter holds true particularly for the large histopathologically convergent panel of non-suppurative, lymphohistiocytic encephalitides. A considerable proportion of these cases remains unsolved using conventional diagnostic methods, such as immunohistochemistry (IHC), in-situ hybridization (ISH), and polymerase chain reaction (PCR) techniques for regional neurotropic pathogens 2, 3, 4, 5, 6 .…”