Presumptive steroid-responsive radiculoneuritis in dogs

Background Presumptive steroid-responsive radiculoneuritis (PSRRN) in dogs is a rare condition that is often difficult to distinguish from neoplasia due to overlapping clinical and imaging features. Differentiating between these etiologies is critical to determining prognosis. Hypothesis/Objectives To describe the clinical presentation, diagnostic findings, magnetic resonance imaging (MRI) characteristics, treatment, and outcomes in dogs with PSRRN affecting spinal nerves and nerve roots. Animals Fifteen dogs presented to 2 UK referral centers between 2019 and 2025. Methods Retrospective review of dogs with MRI findings consistent with nerves and nerve roots inflammation involving the C6-T2 or L4-S3 spinal cord segments and a minimum clinical follow-up of 12 months. Results Dogs had a mean duration of 8 weeks (range 4 days-24 weeks) of lameness and monoparesis, and a mean age of 50.6 months (range 12-104 months); 12/15 were male (6 neutered) and 3/15 female (2 neutered). German Shepherd dogs accounted for 4/15 cases. Magnetic resonance imaging consistently revealed contrast-enhancing, T2W, and short τ inversion recovery hyperintense lesions, frequently affecting the L7 and T1 nerves and roots. Lumbar cerebrospinal fluid analysis revealed albuminocytological dissociation in 4/5 dogs. All dogs responded to medical treatment, although 3/15 experienced relapse over a median follow-up of 25 months (range 12-50 months). Conclusions and clinical importance Presumptive steroid-responsive radiculoneuritis should be considered in dogs with diffuse enlargement of spinal nerves and nerve roots and chronic monoparesis. Magnetic resonance imaging findings, while suggestive, are not pathognomonic and highlight the importance of considering inflammatory etiologies in the differential diagnosis of spinal nerve enlargement.