Corticosteroid monotherapy versus combined cytarabine continuous rate infusion and corticosteroid therapy in dogs with meningoencephalitis of unknown origin: A blinded, randomized, controlled trial

Abstract Background Treatment options available for meningoencephalitis of unknown origin (MUO) in dogs are suboptimal, and currently, no single treatment protocol appears to be superior. Objectives Compare neurological deterioration rates at 7 days between dogs with MUO treated with corticosteroids alone or combined with cytosine arabinoside (CA) continuous rate infusion (CRI) and compare clinical deterioration and survival at 30 and 100 days. Animals Sixty‐nine dogs with magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) features or both compatible with MUO. Methods Parallel, blinded, randomized controlled trial. Simple randomization into 2 treatment groups: 4 mg/kg/day prednisolone (or dexamethasone equivalent) for 2 days or 200 mg/m2 CA CRI over 8 hours plus 2 mg/kg/day prednisolone. Blinding of the treatment protocol was carried out using reversible redaction of clinical records, and treatment failure was defined as deterioration of neurological assessment or death. Using intention‐to‐treat analysis, proportions failing treatment at 7, 30, and 100 days were compared using Fisher's exact test. All‐cause mortality at 100 days was compared using Kaplan‐Meier survival curves. Results Thirty‐five dogs were allocated to corticosteroid only, and 34 dogs were allocated to combined CA CRI and corticosteroid. Proportions failing treatment at 7, 30, and 100 days were 7/35 (20%), 9/35 (26%), and 15/35 (43%) in the corticosteroid‐only group and 8/34 (24%), 11/34 (32%), and 23/34 (68%) in the corticosteroid and CA CRI group. All‐cause mortality at 100 days was not significantly different between groups (P = .62). Clinically relevant treatment‐related adverse effects were not observed. Conclusions and Clinical Importance We found no difference in outcome between corticosteroid monotherapy and combined cytarabine CRI and corticosteroid therapy at 7, 30, and 100 days after diagnosis in dogs with MUO.