The optimal treatment for meningoencephalomyelitis of unknown etiology (MUE) remains unknown, despite the widespread use of a variety of immunosuppressive drugs. To compare the efficacy of prednisolone combined with either vincristine and cyclophosphamide (COP group; n= 10) or with cytosine arabinoside (AraC group; n= 9). Nineteen dogs with neurological deficits, neuroimaging, and cerebrospinal fluid abnormalities consistent with a diagnosis of MUE. Prospective, blinded, and randomized clinical trial. Dogs fulfilling the inclusion criteria were randomly allocated to receive 1 drug regimen. Four of 10 dogs in the COP group and 5/9 in the AraC group survived > 12 months but neither the survival time nor the time-to-treatment failure differed between the 2 groups. Treatment with COP resulted in an unacceptable incidence of adverse effects. The adverse effects of COP make it an unsuitable treatment for MUE. Although survival of animals treated with AraC was broadly similar to that reported in recently published studies describing this treatment, it remains unclear whether it confers any benefit over using prednisolone alone.
