Case Report: Spinal proliferative meningitis with arachnoid diverticulum formation in a dog.

This case report describes a 4-year-old Golden Retriever with chronic progressive motor impairment of pelvic limbs. A neurological examination revealed non-painful ambulatory paraparesis, and magnetic resonance imaging detected an eccentric cystic lesion that compressed the thoracic part of the spinal cord. The surgical approach consisted of spinal cord decompression and lesion excision, along with vertebral column stabilization. A neuropathological examination revealed dural and arachnoid hypertrophic calcifying changes with lymphoplasmacytic and neutrophilic infiltration. This is the first documented case of inflammatory meningoproliferative spinal cord disorder associated with arachnoid diverticulum formation in dogs.