A stroke is usually defined as the sudden loss of one or more brain functions that occurs when the blood supply to a part of your brain is interrupted or reduced, depriving the brain of oxygen and nutrients.
Not all strokes are the same! Blood flow to the brain can be compromised in different ways that give rise to the type of stroke.
Ischemic Strokes occur when a blood vessel that supplies or drains the brain is narrowed or blocked, slowing down the blood supply to that part of the brain that depends on them. Loss of blood flow is called ischemia.
Most commonly it is caused by clots (thrombi) or fat plaques (atherosclerosis) affecting an artery. These can originate at the site of the blockage – thrombotic – or can occur when a clot or other debris travel from somewhere else (the heart, a neck vessel) and lodges in a smaller artery interrupting the blood supply (embolism or thromboembolism). Common causes leading to arterial ischemic stroke include cerebral artery dissection, heart conditions such as Patent Foramen Ovale (PFO), the reversible cerebral vasoconstriction syndromes, infections like HIV and TB, genetic conditions, drug abuse, blood disorders, and cancers.
Blood flow can also slow down or stop if the vein draining that part of the brain is blocked by clotting (venous thrombosis). These is called venous ischemia and tends to be less severe if the built up pressure in the system did not cause rupture and bleeding.
Hemorrhagic Strokes occur when a blood vessel in your brain leaks or ruptures inside the brain. Bleeding in the brain causes pressure to the nerve cells and comprises their survival. The bleeding can originate from arteries or veins inside or around the brain. Common causes include the rupture of brain aneurysms, subarachnoid hemorrhage, arterial malformations, blood disorders, the reversible cerebral vasoconstriction syndromes, cerebral venous sinus thrombosis and drug abuse.
Cerebral Venous Sinus Thrombosis (CVST) occurs when blood flow slows down or is blocked by a blood clot (called a venous thrombosis) in the vein that drains the brain. Lack of blood flow in this region is called venous ischemia and tends to be less severe is the build-up in pressure from the blockage does not cause rupture or bleeding. It is possible for the pressure to become too high, causing damage to the vessel and forming a hemorrhage.
Transient ischemic attack (TIA) resembles a stroke, producing similar symptoms, but usually lasts only a few minutes and causes no permanent damage. It occurs due to the temporary blockage of an artery to the brain by a thrombus, that spontaneously passes once again restoring blood flow to the brain.
What happens after a stroke?
The severity and degree of damage to brain tissue after a stroke is not the same for everyone. Since a stroke can happen in many different parts of the brain some people may have trouble with movement, talking, listening or vision, while some people may only experience minor changes. While strokes often cause permanent damage, rehabilitation can help the brain recover and overcome certain obstacles one may face immediately after the stroke. In addition, many factors such as the type of stroke, which part of the brain area was injured, and the age at injury all contribute to a person’s outcome.
Cerebral Venous Sinus Thrombosis (CVST) when a blood clot forms in the brain’s venous sinuses preventing blood from draining out of the brain. As a result, blood leaks into the brain tissues, forming a hemorrhage.
