A 9-year-old 27.1-kg (59.6-lb) neutered male Labrador Retriever was examined because of progressive lethargy, signs of pain, anorexia, pyrexia, and pelvic limb weakness of 3 days’ duration. The owner also noticed progressive weight loss during the preceding 3 months. On initial examination, the dog had a rectal temperature of 40°C (104°F), and the remainder of the physical examination findings were unremarkable. A neurologic examination was performed. Postural reactions in the right thoracic limb and both pelvic limbs were delayed; spinal reflexes were exaggerated. The dog collapsed and assumed sternal recumbency on elevation of the head.