Neurologic manifestations of cerebrovascular atherosclerosis associated with primary hypothyroidism in a dog.

A 6-year-old, obese, spayed female Doberman pinscher dog was presented for clinical examination with a 1-day history of repeated seizures and a long-term history of periodic bouts of ataxia, circling, and head tilt. The seizures were controlled with phenobarbital, but the dog died 2 days after presentation. Necropsy revealed severe, diffuse, follicular atrophy of the thyroid gland (primary hypothyroidism), severe generalized atherosclerosis, severe pseudolaminar cortical necrosis and acute vasculitis in the cerebrum, and congestive heart failure. The neurologic signs were explained by the pseudolaminar necrosis and associated cerebrovascular atherosclerosis. The cerebrocortical necrosis was believed to be caused by tissue hypoxia secondary to progressive vascular occlusion. Cerebrovascular atherosclerosis, secondary to primary hypothyroidism, was considered the most important cause of the hypoxia.