Strokes are to your brain what a heart attack is to your heart. When you have a stroke, part of your brain loses its blood supply, which keeps that brain area from getting oxygen. Without oxygen, the affected brain cells become oxygen-starved and stop working properly.

If your brain cells go too long without oxygen, they’ll die. If enough brain cells in an area die, the damage becomes permanent, and you may lose the abilities that area once controlled. However, restoring blood flow may prevent that kind of damage or at least limit how severe it is. That’s why time is critical in treating a stroke.

Strokes fall into three main categories:

• ischemic stroke
• haemorrhagic stroke
• transient ischemic attack (TIA)

Ischemic stroke

During an ischemic stroke, the arteries supplying blood to the brain narrow or become blocked. Blood clots or severely reduced blood flow to the brain cause these blockages. Pieces of plaque breaking off and blocking a blood vessel can also cause them.

Two types of blockages can lead to ischemic stroke:

A cerebral embolism (embolic stroke) occurs when a blood clot forms in another part of the body — often the heart or arteries in the upper chest and neck — and moves through the bloodstream until it hits an artery too narrow to let it pass. The clot gets stuck, stops the flow of blood, and causes a stroke.

Cerebral thrombosis (thrombotic stroke) occurs when a blood clot develops at the fatty plaque within the blood vessel.

According to leading research, 87% of strokes are ischemic.

Haemorrhagic stroke

A haemorrhagic stroke happens when an artery in the brain breaks open or leaks blood. The blood from that artery creates excess pressure in the skull and swells the brain, damaging brain cells and tissues.

Doctors categorize haemorrhagic strokes into two primary types:

An intracerebral haemorrhagic (ICH) stroke is the most common type of haemorrhagic stroke. It happens when the tissues surrounding the brain fill with blood after an artery bursts.

A subarachnoid haemorrhagic (SAH) stroke is less common. It causes bleeding in the area between the brain and the tissues that cover it.

Transient ischemic attack (TIA)

A TIA, or mini-stroke, occurs when blood flow to the brain is blocked temporarily. Symptoms are similar to those of a full stroke. However, they typically disappear after a few minutes or hours when the blockage moves and blood flow is restored.

A blood clot usually causes a TIA. While it’s not technically a full stroke, a TIA serves as a warning that an actual stroke may happen. Because of this, it’s best not to ignore it. Seek the same treatment you would for a major stroke and get emergency medical help.