The different types of stroke are dependent on the specific cause – is the underlying reason because blood flow has been blocked by blood clots or has a blood vessel ruptured?
Blood vessels or arteries which supply blood to the brain narrow or experience a blockage. Blood clots can severely reduce blood flow, causing a life-threatening situation within a matter of minutes.
The most common types of ischemic stroke are:
- Thrombotic stroke (a blood clot forms in the arteries): A thrombotic stroke is often caused by plaque or fatty deposits which have accumulated in the arteries and result in a blockage known as atherosclerosis.
- Embolic stroke: A blood clot, known as an embolus or other form of debris forms elsewhere in the body, such as the heart and when moving through the blood stream causes a blockage to the blood vessels supplying the brain.
- Transient ischemic attack or TIA: This type of stroke is sometimes referred to as a mini-stroke. Blood flow to the brain becomes blocked for less than 5 minutes. Symptoms as a result of the blockage are temporary and appear to ‘resolve’ within a handful of minutes without a seemingly damaging effect. A TIA is considered a serious form of stroke as well and shouldn’t be taken lightly. In most TIA cases a blood clot is responsible for causing the blockage and serves as a warning for a possible major stroke down the line. It is strongly advisable to seek medical attention for a TIA, as you would for any other major stroke. Arteries may be partially blocked, which places a person at higher risk for a more serious stroke at any stage. A partial blockage can still cause damage to the brain.
Leaking blood from a ruptured artery in the brain can cause excess pressure in the skull. This pressure can lead to swelling and severe damage to cells and tissue as blood accumulates in the tissues surrounding the brain.
Types of haemorrhagic stroke that occur include:
- Intracerebral stroke: When an artery ruptures, tissue surrounding the brain fills with blood, often as a result of high blood pressure, vascular malformations, use of blood-thinning medications, and trauma.
- Subarachnoid stroke: Bleeding occurs between the brain and tissues surrounding it and is typically associated with a sudden and intense headache. A small sack-shaped pouch on an artery (an aneurysm) ruptures, causing blood vessels to widen and narrow erratically, which leads to the rupturing of the blood vessels during a subarachnoid haemorrhage stroke.
Hypertension (uncontrolled high blood pressure), aneurysms (weak spots in the walls of blood vessels) and overtreatment with anticoagulants (blood thinning substances) are often underlying causes of a haemorrhagic stroke. Less common causes include arteriovenous malformation (a rupturing of a blood vessels which are abnormal or thin-walled), which is often present at birth.