Bush Veterinary Neurology Service is proud to publish the Neurotransmitter 2.0 Technically Speaking; a newsletter written by our technicians for technicians.
Strokes – Diagnosis, Treatment and Prognosis
By the BVNS Springfield Staff
A stroke, also known as a cerebrovascular accident, is defined as any sudden loss of blood supply to the central nervous system. Strokes can be broken down into two categories: ischemic and hemorrhagic.
Ischemic strokes are caused by a blockage or obstruction in the blood vessels such as blood clots, platelet clumping, bacteria, tumor cells or parasites. Hemorrhagic strokes are caused by bleeds in the brain from ruptured blood vessels, malformed blood vessels, cancer affected blood vessels or clotting disorders. Ischemic strokes in the spinal cord are most commonly caused by a blockage caused by a piece of connective tissue obstructing a blood vessel. Transient ischemic attacks are strokes that have a sudden onset and resolve within 24 hours.
Clinical Signs
Depending on where the stroke occurs in the brain, patients may show different clinical signs. Strokes that occur in the forebrain may cause patients to circle toward the affected side, they may be uncoordinated, exhibit head pressing, develop weakness on the side opposite to the stroke, or have seizures.
When the event occurs in the vestibular system, there may be a head tilt toward the affected side, nystagmus, postural issues, and nystagmus.
When the damage occurs in the cerebellum patients can have nystagmus, balance and coordination issues, tremors, or a stiff body posture.
Strokes can occur at any age, and Greyhounds and Schnauzers are some of the most common breeds to suffer from strokes.
Diagnosis
Diagnosis is determined by a complete evaluation of all body systems in order to identify possible underlying causes. Blood and urine should be analyzed in order to effectively rule out metabolic causes.
Dogs with hypothyroidism are prone to hyperlipidemia, which is characterized by the accumulation of plasma lipids and cholesterol and can increase the risk of ischemic events in the brain. Metabolic disorders that increase hypercoagulability can also increase the risk of ischemic events. Disturbances in the cardiovascular system should be assessed as hypertension and atrial fibrillation can lead to infarcts in the brain.
An MRI should be performed in order to rule out other intracranial causes for clinical signs such as neoplasia, immune-mediated inflammation or infection. Signal changes in the diffusion-weighted imaging sequence indicate cytotoxic edema caused by ischemic events. Initially, the subtle changes that occur in the brain may not be visible on MRI and are more easily identified during the later stages of a stroke.
Treatment
Treatment of strokes is largely supportive, but the outcome of diagnostic testing can help determine treatments necessary for the underlying cause of the stroke and help prevent future events.
Treatment can include but is not limited to: monitoring at home, hospitalization for continued monitoring and preventative maintenance. At-home care for patients should consist of close monitoring to help determine improvement or decline. Progress, even slow improvement, is a good sign.
Some stroke patients require extensive attention including hand feeding, help ambulating and monitoring or assistance with elimination.
Hospitalization may be necessary for stroke patients, especially if the stroke resulted in seizures, severe vestibular signs or mentation changes.
Patients that have seizures will likely need to be hospitalized for at least 24 hours and released once the patient is seizure-free, stable and the owners are comfortable with at-home care. They will also likely need to be on life-long anti-epileptic medications; once seizure potential has been identified in an animal, they can continue to have seizures.
The care associated with vestibular signs includes managing severe nausea, including IV fluids to help with hydration, and anti-emetics.
Prognosis
The prognosis for strokes (both ischemic and hemorrhagic) depends on the severity of the stroke, response to supportive care, and if there is an identified underlying cause. Dogs or cats with an underlying disease have a poorer prognosis and are more likely to suffer from another stroke.
Common underlying diseases in dogs include hyperadrenocorticism, chronic kidney failure, heartworm disease, neoplasia, and hypothyroidism. In cats, common underlying diseases include hyperthyroidism, hypertrophic cardiomyopathy, chronic kidney failure, diabetes mellitus, and neoplasia.
Most pets who suffer from an ischemic stroke with no underlying condition have a fair to good prognosis and recover within several weeks with supportive care. However, there is the possibility of an acute death within thirty days of the vascular event and so careful monitoring is always recommended.
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References
1. Brooks, W. (2006, July 17). Vascular Accidents (Strokes) in the Brains of Dogs and Cats – Veterinary Partner. Retrieved from https://veterinarypartner.vin.com/default.aspx?pid=19239&id=4952504
2. Gredal, H., Toft, N., Westrup, U., Motta, L., Gideon, P., Arlien-Søborg, P., . . . Berendt, M. (2012, December 1). Survival and clinical outcome of dogs with ischaemic stroke. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/23206661
3. Platt, S. (2008, August). Canine Stroke. Retrieved from https://www.vin.com/apputil/content/defaultadv1.aspx?id=3866650&pid=11268&
4. An Update on Cerebrovascular Disease in Dogs and Cats by Christen Elizabeth Boudreau
5. Vascular Accidents (Strokes) in the Brains of Dogs and Cats by Wendy C. Brooks
6. Choi, Sooyoung & Noh, Daji & Kim, Youngwhan & Jeong, Inseong & Choi, Hojung & Lee, Youngwon & Lee, Kija. (2017). Magnetic resonance imaging characteristics of ischemic brain infarction according to time passage in a canine stroke model. Journal of veterinary science. 19. 10.4142/jvs.2018.19.1.137.
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