The World Stroke Organization established World Stroke Day in 2006 to demonstrate how significantly important it is to increase awareness and information about this life-threatening condition. Stroke is the second leading cause of death worldwide and a foremost contributor to disability. Data from a study in 2020 found stroke affected approximately 13.7 million people and close to 5.5 million deaths every year.

One in four people will have a stroke during their lifetime!

Strokes can be caused by bleeding or a burst blood vessel in the brain, or from a blocked artery or blood clot. When the stroke is instigated by a clot it is called an ischaemic stroke, which is the most common type. Approximately 87% of strokes are ischaemic. It occurs when the blood vessels in the brain become blocked or narrowed, leading to diminished blood flow to the brain.

Blocked or blood vessels with restricted blood flow commonly result from a build-up of fatty deposits or clots from other debris which have travelled through the blood stream. These usually come from the heart and imbed themselves in the brain’s blood vessels.

What happens to the brain after a stroke?

For each hour a person experiences an ischaemic stroke, this is what is lost:

• 120 million neurons (nerve cells which send and receive signals).
• 830 billion synapses (junction where neurons communicate with each other).
• 714km of myelinated fibres (nerve fibres wrapped in a myelin sheath which insulates the fibre and improves electrical signals). 

However, damage starts immediately!

1.9 million neurons, 14 billion synapses, 12km of myelinated fibres are destroyed every minute.

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History of stroke

Hippocrates first used the term ‘apoplexy’ to describe a group of neurological conditions, including stroke. It was defined as “stagnation or blockage of the blood's circulation, whereby all motion and action of the spirit were (suddenly) taken away from the living human body causing a complete biomechanical shutdown”. Referencing Hippocratic views, any blockage or clot may cause an excess of blockages in the brain, resulting in ‘apoplexy’.

Thrombosis and stroke

A blood clot in a vein, such as deep vein thrombosis (DVT) rarely causes a stroke. A clot in an artery, arterial thrombosis, can cause a stroke. Ischaemic obstruction produces two types of conditions – thrombotic and embolic. Thrombotic stroke develops when there is a build-up of plaque which constricts blood flow (usually due to atherosclerosis) and narrows the vascular chamber creating a blood clot. Embolic stroke occurs when there is a reduction in blood flow to the brain resulting in an embolism, instigating serious stress and eventually the death of brain cells. Another term associated with these types of strokes is cerebral arteriosclerosis, which is a disease where the arteries in the brain become hard, thick and narrow due to the fatty deposits within the artery walls.

Factors which may increase the risk of a stroke:

Lifestyle

• Obesity
• Physical inactivity
• Excessive alcohol intake
• Smoking

Medical

• High blood pressure
• High cholesterol
• Diabetes
• Obstructive sleep apnea
• Cardiovascular disease
• Genetic history

Other

• Age – 55+.
• Race or ethnicity – African Americans and Hispanics.
• Sex – men have a higher risk.
• Hormones – oral contraceptives or hormone replacement therapies.

If you would like some information about atherosclerosis and cardiovascular disease, please visit our webpage CVD and thrombosis.

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References

• Kuriakose, D., & Xiao, Z. (2020). Pathophysiology and treatment of stroke: present status and future perspectives. Int J Mol Sci.;21(20):7609. doi: 10.3390/ijms21207609. PMID: 33076218.
• Saver, J.L. (2006). Time is brain - quantified. Stroke, 37.1: 263–266.
• Tsoucalas, G., Papaioannou, T.G. & Karamanou, M. (2019). The Hippocratic Doctrine of ‘the acute brain suffering’ as the brain stroke.” Journal of stroke and cerebrovascular diseases , 28.2: 412–417.
• Stroke - Symptoms and causes - Mayo Clinic
• What is Venous Thromboembolism? | CDC
• Hypercoagulability - StatPearls - NCBI Bookshelf (nih.gov)
• Cerebral Arteriosclerosis | National Institute of Neurological Disorders and Stroke (nih.gov)