A staggering 100,000 people suffer a stroke in England and Wales each year. Andy Stenson takes a closer look at this debilitating condition
To understand a stroke and its implications, we must first consider what one is. For the human brain to function at peak levels, blood must flow through its many vessels. If blood flow is obstructed to any part, the brain loses its energy supply and becomes injured. If blood is obstructed for more than several minutes, the brain cells' injury becomes permanent and tissue dies in the affected region. The loss or alteration of bodily function that results from an insufficient supply of blood to part of the brain is called a stroke.
Strokes are generally divided into two groups, with sub-groups in each. If we consider an isolated blood vessel, blood flow to the brain tissue can be hampered in two ways:
• The vessel clogs (ischaemic stroke).
• The vessel ruptures, causing blood to leak into the brain (haemorrhagic stroke).
Ischaemic strokes
Ischaemic strokes account for about 83% of all cases. It results from an obstruction, typically a blood clot, called a cerebral thrombosis or cerebral embolism.
Ischaemic strokes occur as a result of an obstruction within a blood vessel supplying blood to the brain. The underlying condition for this type of blockage is the development of fatty deposits lining the vessel walls. This condition is called atherosclerosis. These fatty deposits can cause two types of obstruction:
• Cerebral thrombosis, which refers to a thrombus (blood clot) that develops at the clogged part of the vessel.
• Cerebral embolism, which refers generally to a blood clot that forms at another location in the circulatory system, usually the heart and large arteries of the upper chest and neck. A portion of the blood clot breaks loose, enters the bloodstream and travels through the brain's blood vessels until it reaches vessels too small to let it pass. A second important cause of embolism is an irregular heartbeat, known as atrial fibrillation. It creates conditions where clots can form in the heart, dislodge and travel to the brain.
Haemorrhagic stroke
Haemorrhagic stroke accounts for about 17% of stroke cases. It results from a weakened vessel that ruptures and bleeds into the surrounding brain. The blood accumulates and compresses the surrounding brain tissue. The two types of haemorrhagic strokes are cerebral haemorrhage or sub-arachnoid haemorrhage.
Haemorrhagic stroke occurs when a weakened blood vessel ruptures. Two types of weakened blood vessels usually cause haemorrhagic stroke: aneurysms and arteriovenous malformations (AVMs):
• An aneurysm is a ballooning of a weakened region of a blood vessel. If left untreated, the aneurysm continues to weaken until it ruptures and bleeds into the brain.
• An arteriovenous malformation (AVM) is a cluster of abnormally formed blood vessels. Any one of these vessels can rupture, also causing bleeding into the brain.
• Also called TIAs, transient ischaemic attacks are minor or warning strokes. In a TIA, conditions indicative of an ischaemic stroke are present and the typical stroke warning signs develop. However, the obstruction (blood clot) occurs for a short time and tends to resolve itself through normal mechanisms.
Even though the symptoms disappear after a short time, TIAs are strong indicators of a possible major stroke. Steps should be taken immediately to prevent a stroke. Factors that can increase the risk of stroke are:
• Increasing age. The chance of having a stroke more than doubles for each decade of life after age 55. While stroke is common among the elderly, many people under 65 also have strokes.
• Sex. The most recent data show that, overall, the incidence and prevalence of stroke are about equal for men and women. However, at all ages, more women than men die of stroke.
• Heredity and race. The chance of stroke is greater in people who have a family history of stroke.
• Prior stroke. The risk of stroke for someone who has already had one is increased many times.
• High blood pressure. High blood pressure is the most important risk factor for stroke. In fact, stroke risk varies directly with blood pressure. Many people believe the effective treatment of high blood pressure is a key reason for the accelerated decline in the death rates for stroke.
• Cigarette smoking. In recent years, studies have shown cigarette smoking to be an important risk factor for stroke. The nicotine and carbon monoxide in cigarette smoke damage the cardiovascular system in many ways. The use of oral contraceptives combined with cigarette smoking greatly increases stroke risk.
• Diabetes mellitus. Diabetes is an independent risk factor for stroke and is strongly correlated with high blood pressure. While diabetes is treatable, having it increases a person's risk of stroke. People with diabetes often also have high cholesterol and are overweight, increasing their risk even more.
• Carotid artery disease. The carotid arteries in your neck supply blood to your brain. A carotid artery damaged by atherosclerosis ' a fatty build up of plaque in the artery wall ' may become blocked by a blood clot, which may result in a stroke. If you have a diseased carotid artery, your doctor may hear an abnormal sound in your neck, called a bruit, when listening with a stethoscope.
p Heart disease.People with heart problems have more than twice the risk of stroke compared to those whose hearts work normally. Atrial fibrillation (the rapid, uncoordinated beating of the heart) in particular raises the risk for stroke. Heart attack is also the major cause of death among stroke survivors.
• Transient ischaemic attacks (TIAs). A person who has had one or more TIAs is almost 10 times more likely to have a stroke than someone of the same age and gender who has not.
• High red blood cell count. A moderate or marked increase in the red blood cell count is a risk factor for stroke. The reason is that more red blood cells thicken the blood and make clots more likely.
• Excessive alcohol intake. Excessive drinking, an average of more than one drink a day for women and more than two drinks a day for men, and binge drinking can raise blood pressure, contribute to obesity, high triglycerides, cancer and other diseases, cause heart failure and lead to stroke.
• Drug abuse. Intravenous drug abuse carries a high risk of stroke from cerebral emboli. Cocaine use has been closely related to strokes, heart attacks and a variety of other cardiovascular complications.
Andy Stenson is senior life and disability underwriter of Scottish Equitable Protect
