Strokes are acute vascular injuries in the central nervous system (often the brain). They occur because of a sudden onset of dysfunction in the brain caused by an abnormal blood supply. The abnormal blood supply occurs for one of two reasons: ischemia (or lack of blood) or hemorrhage.
An ischemic event occurs due to obstruction of a blood vessel. In the case of thrombosis, the obstruction (typically a blood clot) develops within a clogged vessel. In the case of an embolism, the blood clot forms somewhere else and travels through the vessels to the site of the occlusion.
When a hemorrhage is to blame for a stroke, it’s because a ruptured blood vessel is leaking. This blood then expands in the spaces around the brain tissue, causing compression.
In both cases, the brain tissue loses blood supply, either from an inherent lack of blood or from compression, and eventually the tissues will die off, causing clinical signs.
Clinical signs of strokes generally start abruptly. In the case of ischemic events, signs typically don’t progress after a few hours, but hemorrhagic vascular injuries may get worse over time and can be fatal.
Clinical signs depend on where in the brain the accident occurs. Major strokes can lead to seizures, coma, and death. Mild strokes in our pets may go unnoticed or chalked up to old age or behavior change. Head tilts, gait abnormalities, unequal pupils, slow reflexes, and tremors are just some of the clinical signs of strokes in pets, but all of these can also occur for other more benign reasons.
Strokes can occur for many reasons, but often the underlying cause is unknown. In some cases, blood vessels are weakened due to genetics or chronic disease. In the dog, strokes can also occur secondary to a very long list of conditions, including:
Sepsis, or blood infections
Tick borne disease, such as Ehrlichia and Rocky Mountain Spotted Fever
High blood pressure
Hyperadrenocorticism, or Cushing’s Disease
Diagnosis might be made based on your pet’s clinical signs and health history, or with brain imaging, such as a CT scan or MRI may be needed. The increasing availability of brain imaging in veterinary medicine shows us that strokes, while still rare, are occurring in our pets more often than we initially thought.
Treatment will vary, depending on the underlying cause for the stroke and the severity of the clinical signs. One lucky break for pets, however, lies in the part of the brain that controls voluntary movement. So often in humans, strokes can be devastating, leaving the patient partially paralyzed. In pets, though, voluntary muscle activity is controlled in a different part of the brain, so strokes are often less obvious in pets.
If you think something might be up with your pet, whether it’s a subtle change in behavior or a more obvious gait abnormality or head tilt, check in with your veterinarian. While odds are that a stroke isn’t to blame, it’s good to rule it out or check for underlying causes.
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