Cyclosporine and prednisolone treatment leads to fewer relapses compared with prednisolone alone in dogs with suspected meningomyelitis of unknown origin.

Objective: The use of cyclosporine as an add-on therapy for meningitis or meningomyelitis of unknown origin (MUO) with only spinal cord involvement has never been described in dogs. The objective of this retrospective study was to evaluate the potential efficacy of cyclosporine combined with prednisolone compared with prednisolone alone in dogs with suspected spinal MUO.

Methods: A retrospective study was conducted on dogs with a presumed diagnosis of spinal MUO treated with prednisolone and cyclosporine (group A) or prednisolone alone (group B) from 2018 to 2023. A positive outcome was defined as a resolution of clinical signs for at least 1 year after diagnosis, and a negative outcome was defined as lack of improvement or relapses within 1 year of presentation.

Results: 47 dogs were included. Twenty-one dogs were included in group A: 16 (76%) recovered, but clinical relapses were observed in 3 (14%). Twelve (57%) showed a positive outcome. Twenty-six patients were enrolled in group B: initial recovery was observed in all dogs, but 16 (62%) showed clinical relapses, 1 (4%) died due to pulmonary complications, and 9 (35%) had a positive outcome. The side effects were mostly mild: 48% in group A and 31% in group B. No significant associations were found between the outcome and the groups.

Conclusions: Prednisolone alone was significantly associated with a higher recovery rate but with a greater frequency of relapses compared with cyclosporine/prednisolone.

Clinical relevance: Cyclosporine could be considered a valid additional treatment in dogs with spinal MUO, potentially leading to a lower recurrence rate than prednisolone alone.