Long-term outcomes and prognostic factors in dogs with meningoencephalitis of unknown origin and suspected necrotic lesions on magnetic resonance imaging: 37 cases (2007-2020)

OBJECTIVE To describe the long-term outcomes, overall survival, progression-free survival, and prognostic factors in dogs with necrotizing encephalitis (NE). ANIMALS 37 client-owned dogs clinically diagnosed with NE. METHODS All dogs underwent MRI and CSF analysis. Cox proportional hazards regression was used to examine factors related to the risk of relapse and death, including signalment, history, diagnostic investigation results, and treatments be- fore the first relapse. RESULTS The medians of the overall and progression-free survival times were 639 days (IQR, 342 to 1,482 days) and 233 days (IQR, 111 to 775 days), respectively. Overall survival was highly correlated with progression-free survival. Four dogs (11%) died or were euthanized within 3 months of diagnosis. Relapse within 6 months was associated with a shorter overall survival. However, no prognostic factors for overall survival were found. The category of patients with pre- senting clinical signs that lasted 29 days to 6 months (OR, 3.26; 95% CI, 1.35 to 7.90) was associated with a higher risk of relapse. Seizures were presented in 75.7% of dogs, with a recurrence rate of 100%. CLINICAL RELEVANCE This report provides comprehensive follow-up information for dogs with NE, revealing a fair prognosis and low early mortality rate. Seizure is a very common clinical sign with a high recurrence rate.