Feline meningoencephalomyelitis of unknown origin: A retrospective analysis of 16 cases.

This study aimed to describe the signalment, clinical signs, magnetic resonance imaging (MRI) findings, cerebrospinal fluid (CSF) analysis, treatment, and outcome of feline meningoencephalomyelitis of unknown origin (FMUO). Medical records from 16 cats meeting the inclusion criteria of CSF pleocytosis, negative CSF polymerase chain reaction (PCR)-infectious disease results, and characteristic MRI findings were retrospectively reviewed. Median age was 9.4 years. Clinical signs included ataxia, proprioceptive deficits, seizures, and spinal hyperesthesia. The CSF nucleated cell count was increased (median 70.7 cells/μL), with predominantly mixed pleocytosis and CSF protein concentration was increased in 15/16 cats. Magnetic resonance imaging showed intraparenchymal infiltrative ill-defined lesions in 13 cases. All cats received a corticosteroid-based treatment protocol; additional therapies included lomustine, cytarabine, and anticonvulsant medications. Mild neurological signs were recorded in 5/12 cats but 7/12 cats were neurologically normal at re-examination. This represents the first study of feline MUO, highlighting FMUO as an important differential diagnosis in cats with variable neurological presentation. Prognosis appears to be good with immunomodulatory therapy.