Abstract: Background - Severe meningoencephalitis of unknown etiology (MUE) typically carries a guarded prognosis. Standard cytarabine arabinoside (CA) dose for MUE is 100-300 mg/m2.
Objective - Describe clinical outcome of 62 dogs with severe MUE treated with monthly 600 mg/m2 CA
Animals - 62 client-owned dogs from a private specialty hospital
Methods: All dogs presenting within a 30-month period with rapidly progressive severe neurological abnormalities with marked MRI and/or CSF changes suggestive of MUE were included. 600 mg/m2 CA was initially administered intravenously over 6-12 hours, followed by monthly 600 mg/m2 subcutaneous CA for a minimum of 6 months or until death.
Results: No severe negative effects were noted with 600 mg/m2 CA. Immunosuppressive corticosteroids were used for ≤7 days in all dogs before tapering. 38/62 (61%) dogs returned to normal with survival times > 6 months. 36/62 (58%) dogs showed dramatic neurological improvement within 48 hours of the initial dose of CA. 25/62 (40%) dogs died due to poor disease control (median time to death=24 days, mean=84 days, range 1-340 days), including 9/14 (64%) dogs with thoracolumbar myelitis and 6/7 (86%) dogs with suspected necrotizing disease. Negative medication effects were mild and attributed to corticosteroids as they resolved with taper.
Conclusions: 600 mg/m2 cytarabine was well tolerated and effectively controlled disease in the majority of dogs with severe MUE. Corticosteroids were tapered rapidly in most dogs, minimizing negative treatment side effects and suggesting disease control was likely attributable to CA. Necrotizing diseases and thoracolumbar myelitis carried a more guarded prognosis.
