Asymmetric lumbosacral transitional vertebra and subsequent disc protrusion in a cocker spaniel.

A 10-year-old cocker spaniel bitch presented with severe lumbosacral pain and acute onset left pelvic limb lameness. A diagnosis of asymmetric lumbosacral transitional vertebra with disc protrusion at L6-L7 was made by computed tomography. The cauda equina and left L6 nerve root were surgically decompressed with a dorsal laminectomy and lateral foraminotomy, which led to rapid resolution of the clinical signs.