Generally, the main cause of stroke is bleeding or blockage of blood vessels, which either lowers or reduces the blood supply to the brain. Due to this, a sufficient amount of nutrients and oxygen is not available to the brain, which in turn leads to the death of brain cells.
Though a stroke generally takes place in the above-mentioned manner, the causes of different types of strokes are distinct.
An ischemic stroke takes place when blood cannot flow to the brain due to a blood clot. This blood clot is usually due to atherosclerosis which refers to the build-up of fat deposits on a blood vessel’s inner lining. A part of the fat deposits can break and cause blockage to the blood flow into the brain. The entire concept is similar to what happens during a heart attack, where a blood clot blocks the blood flow to a part of the heart.
A haemorrhagic stroke occurs when blood is spilled into the surrounding tissues due to the breaking of or rupturing of a blood vessel in the brain. Haemorrhagic strokes are further classified into three major types. The first one is an aneurysm, which leads to a part of the weakened blood vessel ballooning outward and rupturing sometimes.
The second one is an arteriovenous malformation in which the blood vessels are formed in an abnormal manner. If a rupture occurs in such an abnormally formed blood vessel, a hemorrhagic stroke can take place. Thirdly, substantially high blood pressure can weaken the small blood vessels in the brain, thereby resulting in bleeding into the brain.
TIA occurs when anything causes a temporary blockage to the blood flow to the brain. The blood clot and the symptoms of TIA last for a short period.
An ICH is caused because of bleeding within the brain tissue. It is commonly caused due to hypertension, arteriovenous malformations, or head trauma.
Subarachnoid haemorrhage is caused due to bleeding in the surrounding spaces of the brain. A ruptured aneurysm, AVM, or head injury are some of the reasons which can cause SAH.
A blood clot that is formed somewhere else in the body and travels through the bloodstream into the brain bears the potential to cause an embolic stroke. It is found that around 15% of all embolic strokes occur in humans having atrial fibrillation, which is a kind of abnormal heart rhythm characterised by an ineffective beating of the heart’s upper chambers.
A thrombus or blood clots developed in the arteries which supply blood to the brain possess the capability of causing a thrombotic stroke.