The brain needs oxygen and nutrients like glucose to provide energy to support normal body function. They’re delivered to the brain through the blood. If the blood supply is disrupted, the brain is deprived of oxygen and nutrients, which results in neurologic dysfunction. An obstruction in a blood vessel with loss of blood supply to an area of the brain is called in infarction. An infarction is also called a stroke.
In most dogs, we don’t know the reason for the infarction. Infarctions can occur secondary to a blood clot, bacterial infection, inflammation or invasion of blood vessels by cancer cells. Rarely, dogs can develop atherosclerosis, similar to people: cholesterol and fat accumulate in the blood vessel wall, obstructing normal flow. Dogs with low thyroid hormone levels or increased fat in their blood are more prone to atherosclerosis. Other disorders that may be associated with infarctions include high blood pressure, diabetes and kidney disease. Hemorrhage into the brain can occur with cancer or disorders that decrease the ability to form blood clots, such as rat poison and anticoagulant drug therapy.
Clinical signs depend on the location of brain injury. Signs come on suddenly and usually one side of the body is more affected than the other. Common clinical signs include abnormal behavior, head-tilt, blindness in one eye and seizures. A presumptive diagnosis of a stroke can be made with MRIs. These are done in specialty practices or at universities. Other diagnostic tests are performed to rule out other neurological diseases that produce similar signs to a stroke. These include routine blood tests, blood pressure measurements, and blood clotting tests.
Most animals show gradual improvement over days to weeks. Prognosis varies with the severity of neurologic damage. Maximum recovery is usually seen within three months. Recurrence is possible, especially in animals with an underlying disease process that cannot be well controlled.
Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum