Stroke (Vascular Accidents) in Pets

What Causes a Stroke?

A stroke can be caused by anything that blocks an artery supplying oxygen-rich blood to the brain. A common cause of stroke in pets is a thrombus or embolus that lodges in a blood vessel supplying the brain. When this happens, the condition is called thromboembolism or embolism.

The underlying cause can be identified in approximately 50% of dogs with vascular accidents, and about 30% of these dogs have hypertension (high blood pressure).

A vascular accident can also happen when there is bleeding in a small area of the brain, a tumor in a blood vessel that interferes with blood circulation, a temporary spasm of a blood vessel, or the presence of inflammation that interferes with blood flow to the brain.

When the brain is deprived of blood circulation and oxygen, the neurons can be injured or killed. This can lead to a loss of function and integrity that is dictated by the area of the brain that’s affected.

Signs of Stroke in Pets

The symptoms exhibited by dogs and cats affected by stroke will depend to a large extent on two important factors:

1. The area(s) of the brain that has been affected

2. The degree and length of time the area was deprived of blood and oxygen

Some stroke symptoms are reversible or partly reversible, while others are irreversible. A stroke is generally non-progressive after the first 72 hours of onset.

Common symptoms include:

• Change in mental alertness
• Loss of certain eye reflexes
• Nystagmus (back and forth eye movements)
• Weakness on one side of the body
• Weakness of the legs
• Walking in circles or wobbly movements
• Head pressing
• Head tilt
• Tremors or seizures

Factors That Increase a Pet’s Risk of Stroke

The incidence of vascular accidents is significantly less common in pets compared to humans. In dogs, approximately 50% of stroke cases have high blood pressure. The most common factors that can increase a dog’s risk of vascular accident include:

• Cushing’s disease
• Chronic kidney failure
• Heartworm disease
• Hypothyroidism-related atherosclerosis
• Abnormally high blood fat levels (usually in miniature schnauzers)
• Cancer

In cats, high blood pressure accompanies about 30% of vascular accidents. The common underlying medical conditions include:

• Hyperthyroidism
• Chronic kidney failure
• Diabetes mellitus
• Hypertrophic cardiomyopathy
• Migrating heartworm larvae
• Migrating Cuterebra larvae

Breed Predispositions

Some dog breeds appear to have higher risks of stroke. These breeds include:

1. Greyhounds are significantly more likely to be evaluated because of ischemic stroke, compared with all other dog breeds combined.

2. Cavalier King Charles Spaniels appear predisposed to ischemic strokes which are characterized by a sudden blockage of the blood supply to a part of the cerebellum. The blockage may be caused by the rupture of an artery in the cerebellum or a blood clot.

In cats, there is no particular breed that has been identified as having a higher risk of having a vascular accident.

How Strokes are Diagnosed in Animals

A dog or cat that is suddenly exhibiting neurologic symptoms could have suffered from a vascular accident. However, there is a need to eliminate other potential causes such as poisoning, head trauma, metabolic disease, infection, or even cancer.

The onset of vascular accidents is sudden and may progress over 24-72 hours. Gradual or partial recovery may follow, except if death occurred as a result of a severe initial injury.

Hemorrhagic stroke (bleeding accidents) tends to be more severe than clotting accidents (thrombosis or embolism). The good news is that hemorrhagic strokes are far less common in pets than they are in humans.

After a thorough physical exam and measurement of blood pressure by a veterinarian, basic blood and urine tests will be performed. Other tests may be recommended depending on the patient’s medical history and initial findings.

Magnetic resonance imaging (MRI) can reveal if there is a hemorrhage, blood clot, or structural changes in specific areas of the brain. Both radiography (x-ray) and CT-scan are not as adequate and sensitive enough to detect damaged areas of the brain or blood clots compared to MRI.

Another test that can be used to distinguish a vascular accident from other types of conditions affecting the nervous system is thromboelastography (TEG). Your vet may refer you to a veterinary neurologist for more specialized care and medical intervention.

Treatment Options for Pets That Have Suffered a Stroke

The treatment regimen for vascular accidents in pets primarily involves supportive care. There is no specific treatment for stroke. Oxygenation of the brain should be maximized to provide a healthy environment for the healing of damaged nerves.

Specific medications will also be given to address the symptoms exhibited by a cat or dog, such as seizures, increased intracranial pressure, high blood pressure, or abnormal bleeding.

In severe cases, patients may need special home care and physical therapy to help regain function and mobility. Compromised patients, however, will need hospital confinement for intensive nursing care, including supplemental oxygen or ventilator to assist breathing, feeding tube, and other procedures that may be necessary depending on how much function was lost or affected.

Prognosis and Recovery

Prognosis and recovery time depend on the extent of damage that occurred in the brain and how quickly treatment was started. Pets with underlying diseases that predisposed the vascular accident generally have shorter survival times. They also have a higher risk of recurrence.

Read more:

Vestibular Disease in Dogs

Seizures in Cats

Seizures in Dogs

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