Long-term observations of feline meningoencephalitis of unknown etiology: clinical, CSF, and MRI findings

A 4-year-old female, neutered Turkish Angora cat presented with acute onset of obtundation, right-sided head turn, and rolling. Postural reactions were either absent or decreased in all four limbs. Cranial nerve examination (menace response, pupillary light, and oculocephalic reflex) were absent or decreased. Magnetic resonance imaging (MRI) demonstrated demarcated lesions in the thalamus and brainstem, which were marked hyperintense on T2-weighted and fluid-attenuated inversion recovery images and isointense on T1-weighted images. Cerebrospinal fluid (CSF) nucleated cell count was markedly elevated (258 cells/µl) with a neutrophilic pattern. The CSF polymerase chain reaction for infectious agents was negative. Feline meningoencephalitis of unknown etiology (FMUE) was the most promiment diagnosis. The cat underwent prednisolone monotherapy (3 mg/kg, twice daily), gradually tapered off. Follow-up clinical signs, MRI, and CSF analysis were performed at 33, 118, and 611 days after the initial therapy. At 33rd days, abnormalities of clinical signs, MRI, and CSF had almost disappeared. At 139th days, since all examinations showed normal findings, treatment stopped. At 611th days, the final examinations showed no remarkable findings. This is the first case describing changes in the clinical signs, MRI findings, and CSF analysis of FMUE with long-term follow-up.