Clinical presentation, prognostic factors, and outcomes of meningoencephalitis of unknown origin in older dogs

BACKGROUND: The clinical presentation and outcomes of older dogs with meningoencephalitis of unknown origin (MUO) have not been described previously. HYPOTHESIS/OBJECTIVES: Compare clinical presentations and outcomes of an older cohort (≥8 years old) of dogs diagnosed with MUO compared to a younger cohort. ANIMALS: Client-owned dogs diagnosed with MUO including 71 dogs ≥ 8 years old and 142 control dogs < 8 years old. METHODS: Multicenter retrospective case-control study. Data were collected from the clinical records of 2 referral centers and referring veterinarians were contacted for additional survival data. Survival and relapse rates of the older and younger cohorts were compared. RESULTS: On presentation, older dogs were found to be significantly more likely to have behavior changes (P = .01), cranial nerve deficits (P < .001), and comorbidities (P < .001) compared with younger dogs. On multivariate analysis, median survival time between the 2 groups did not differ significantly (16 months for older dogs and 24 months for younger dogs, P = .48). No significant difference was found in relapse rates between the 2 groups: 67/103 (65.0%) younger dogs and 20/48 (41.7%) older dogs relapsed within the study period. CONCLUSIONS AND CLINICAL IMPORTANCE: Older dogs with MUO were found to have similar survival times and relapse rates compared to younger dogs with MUO.