Clinical signs, diagnostic imaging, histopathology and outcome in a dog with meningoencephalomyelitis of unknown origin and concurrent involvement of the cauda equina and left sciatic nerve

Abstract A 3‐year‐old, female, neutered toy poodle dog was presented with generalised tremors, neck pain and obtundation. Neurological examination revealed a multifocal localisation (brainstem and cervical spinal cord). Magnetic resonance imaging findings and cerebrospinal fluid tap were consistent with meningoencephalomyelitis of unknown origin. After immunosuppressive treatment, the dog improved, but while tapering experienced two relapses. During the second relapse, clinical presentation revealed multifocal clinical signs affecting the brainstem, the lumbosacral spinal cord and the left sciatic nerve. Magnetic resonance imagings of the brain, lumbosacral spinal cord and the left sciatic nerve, cerebrospinal fluid analysis and histopathology of the left sciatic nerve confirmed a recurrence of a meningoencephalomyelitis of unknown origin involving the central nervous system and the peripheral nervous system. Immunosuppressive treatment was re‐instituted, with improvement of clinical signs. At 1‐year follow‐up, the dog remains clinically stable with no treatment.