Presumed optic neuritis of non‐infectious origin in dogs treated with immunosuppressive medication: 28 dogs (2000‐2015)

OBJECTIVE To describe the clinical findings, magnetic resonance imaging features, management and outcome of canine cases with presumed optic neuritis of non-infectious origin that were presented to a UK referral centre from January 2000 to December 2015. MATERIALS AND METHODS The clinical database was searched for optic neuritis. Dogs with acute-onset vision impairment, systemic immunosuppressive treatment and follow-up of ≥6 months were included. Information collected included: age; gender; breed; clinical signs and duration; physical, ophthalmic and neurological examination findings; concurrent systemic disease; and results of electroretinogram, magnetic resonance imaging, cerebrospinal fluid analysis, polymerase chain reaction and serology testing for Toxoplasma gondii, Neospora caninum and canine distemper virus, haematology and serum biochemistry profiles, abdominal ultrasound, thoracic radiography, treatment and outcome. RESULTS Twenty-eight dogs were included, with a total of 48 affected optic nerves. Age at presentation ranged from 6 months to 10.5 years. Fundoscopic evidence of optic nerve disease was present in 34 of 48 (71%) optic nerves. Magnetic resonance imaging revealed enlargement of 32 of 48 (67%) nerves and contrast enhancement of 28 of 48 (58%) nerves. Cerebrospinal fluid analysis performed in 25 of 28 (89%) dogs revealed pleocytosis (>5 nucleated cells/uL) in 11 of 25 (44%) and increased protein (>0.35 g/L) in 11 of 25 (44%). Immunosuppressive prednisolone was administered to all dogs. Prednisolone was used alone in 9 of 28 (32%) dogs; the remaining 19 dogs received a combination of prednisolone with cytosine arabinoside, cyclosporine and/or azathioprine. Vision was recovered in 24 eyes (50%) of 18 affected dogs. CLINICAL SIGNIFICANCE A positive response to treatment was observed in 64% of dogs with presumptively diagnosed optic neuritis treated with immunosuppressive medication.