Why have you had a stroke?

It is surprisingly difficult to tell why someone has just had a stroke. Although a great deal is known about the causes of a stroke, the evidence often disap­pears in the initial stages. For example, if the stroke was caused by a blood clot that has travelled from an abnormality in the heart, a heart scan – carried out to try to find the source of a suspected embolus – will often fail to provide evidence of an abnormal blood clot. This is because the offending clot is now in the brain, having caused the stroke.
Despite these problems, strokes become much more fre­quent as people get older. Strokes can affect the very young (even tiny children), but are very rare at
this age. As our population ages, the average age of a person with a stroke is about 75 years. Stroke gets more common with increasing age; however, better stroke pre­vention has reduced the general risk of stroke. These two factors have worked in opposite directions (age­ing society increasing the number of strokes and better prevention decreasing the number), and overall the numbers of people having strokes in the UK has remained fairly constant over the past two decades. The chance of an 80 year old having a stroke is about 30 times greater than the chance of a 50 year old having one. This is probably the result of wear and tear of the blood vessels. Not a lot can be done about ageing, but it is possible to control other risk factors associated with having a stroke.

ATHEROSCLEROSIS

Atherosclerosis is the name given to the common problem of the hardening and furring up of the arteries. It can start at quite a young age when fatty streaks (atheroma) appear in the blood vessel wall. As people get older, these fatty streaks can cause suffi­cient damage to trigger the forma­tion of a blood clot (thrombus) within the artery, leading to narrowing and a reduced blood flow. These blood clots can eventually block the blood vessel and cause a stroke if the artery leads to the brain. Most ischaemic strokes and TIAs are caused by these types of problems.

You can reduce your risk of atherosclerosis by altering your lifestyle. Eating a low-fat diet, with five portions of fresh fruit and veg­etables daily, and taking regular exercise, will not only decrease the risk of atherosclerosis and help to reduce the risk of having a stroke, but will also protect against other circulatory problems, such as coronary heart disease and high blood pressure. It is particularly important to cut down on saturat­ed fat, found in red meat and dairy products, as this type of fat increases the levels of blood cholesterol, a fatty substance that encourages blood clots to form.

HIGH BLOOD PRESSURE

The medical term for high blood pressure is ‘hypertension’. Most people know that hypertension is bad for you, but far fewer people realise that this is because the higher your blood pressure, the higher your risk of a stroke. When blood is forced through your circu­latory system at high pressure, your artery walls receive a pound­ing. This damages the artery walls so that atherosclerosis and blood clots are more likely to occur.
Blood pressure is measured at two points in the heartbeat cycle. The highest pressure in the circulation occurs when the heart is con­tracting (the systolic pressure) and the lowest when the heart is at rest between beats (the diastolic pressure). This gives a blood pres­sure measurement of two figures (systolic/diastolic), for example, 120/80. Researchers now know that, when your blood pressure rises and remains at a certain level, lowering your blood pressure will reduce your risk of a stroke. This is a rapidly changing subject at the moment, but most blood pressure experts would certainly want your blood pressure to be lower than 150/90. The latest recommend­ations consider a blood pressure below 140/85 to be ideal.
For patients with diabetes, kidney impairment or already have cardiovascular disease a lower target of 130/80 is recommended. Some experts predicted that, if the average blood pressure could be lowered in the UK, there would be a dramatic reduction in the number of people who have strokes.

Reducing your blood pressure

A high salt intake has been linked to high blood pressure. Salt increases blood pressure because it attracts fluid into the circulation, increasing the volume of blood, and reduces the amount of fluid lost through the kidneys. Some experts have sug­gested that some simple measures could dramatically reduce the stroke rate in the whole population. These measures include limiting the amount of salt in processed foods (for example, tinned soup) or labelling the salt content of all foods to allow consumers the chance to avoid salty foods.
Other methods of lowering blood pressure include cutting down on alcohol and taking regular exercise. If all these methods fail, doctors can prescribe safe and effective blood pressure-lowering pills.
Unfortunately, high blood pressure often causes no symp­toms and, even if your blood pressure is dangerously high, you may feel relatively well. It is therefore important to have your blood pressure checked regularly every year or so by your doctor or practice nurse as a routine part of health screening.

SMOKING

Most people know that smoking is bad for their health, but many do not realise just how bad. Recent research has demonstrated that about half of all smokers will die prematurely from a smoking-related disease (for example, a heart attack, chronic bronchitis, a stroke, lung cancer, etc.). These odds of a premature death are considerably more than those for winning the national lottery. The good news is that stopping smok­ing improves your health almost immediately. You can probably halve your future risk of a stroke or a heart attack if you give up smoking. This is far better than any pill that your doctor could prescribe.
If you give up smoking, you will have much better health and also save money. Nicotine replacement therapy, such as patches or gum, can help you give up smoking and are available without a prescription from pharmacies. Some people find that other methods such as hypnosis are also helpful.

HEART CONDITIONS

Atrial fibrillation is the most common heart problem known to increase the chances of having a stroke. It becomes more common as people get older and affects about one in twenty people aged over 65 years old. It occurs when the heart beats irregularly, and increases the chance of blood clots forming in the heart. The blood clots can cause a stroke if they are carried by the circulation from the heart to the brain. Treatment with a blood-thinning medication such as aspirin or warfarin can reduce the risk of a stroke. If you notice that your heart rhythm has become irregular (for example, you experi­ence palpitations), you should go to your doctor for a check-up.

STROKE IN YOUNGER PEOPLE

Although stroke is mainly a disease of elderly people, it can strike at any age, and is a particular tragedy for people under the age of 55 years. The diagnosis is often difficult because stroke is uncommon in this younger age group. The
cause may be unusual and may mimic other complicated medical conditions. For this reason, an opin­ion from a neurologist (a specialist of diseases affecting the brain and nerves) is often very useful.

Causes of stroke in young people

• Brain haemorrhages:

A brain haemorrhage can occur at any age and can be responsible for the rare strokes that affect younger people. Some haemorrhages – from, for example, a dilated weakening of an artery (aneurysm) that may have been present from birth – are so severe that they cause death in min­utes or hours. This sort of stroke is one of the causes of an unexpected death in a previously fit and healthy
person. It often results in a sudden severe headache and collapse, lead­ing to immediate coma. A CT (com­puted tomography) scan can con­firm the diagnosis and patients will need specialised care in hospital. Surgery can be life-saving for some patients, especially those with a bleed resulting from a cerebral aneurysm.

• Heart problems:

Some rare problems affecting the heart can cause stroke in younger people. These are generally conditions that cause blood clots to form in the heart, such as a congenital abnor­mality present from birth. Blood clots can cause strokes if they leave the heart and block an important blood vessel in the brain. If a young person has this type of stroke, he or she often needs to be assessed by a team of doctors, including a heart specialist. Heart ultrasound scans (echocardiograms) involve placing a probe on the chest and may show a hole in the heart or another problem causing abnormal blood clots. Even better pictures can be obtained by placing the probe in the gullet (oesophagus). These scans are called TOEs, short for transoesophageal echocardiograms.

• Damage to a blood vessel:

Blood vessels in the neck can sometimes tear and split. This can cause a stroke if the vessels become blocked or abnormal blood clots are formed. The med­ical term for this problem is called a ‘dissection’. The carotid artery carries the main blood supply to the brain in the front of the neck. This artery can be damaged by trauma to the front of the neck such as attempted strangulation, sports injuries (rugby tackles) and car accidents.

• Abnormal blood clotting:

There are many inherited problems affecting blood clotting (see table) but most of these are rare. Some people have a history of a number of medical problems as a result of blood clots (for example, deep vein thrombosis). Special blood tests are therefore useful, especially if the stroke has occurred before 35 years of age.

• The pill:

The oral contracep­tive pill can cause a stroke in women, but the risk is very small. If 10,000 women take the pill for one year, on average one of these women will have a stroke as a result. These figures are based on the use of the combined pill, which includes an oestrogen and a progestogen. The risk is about three times that of a similar aged woman not on the pill. The risk appears to be higher if you smoke cigarettes. Despite this threefold risk, the chance of a stroke is still tiny, because strokes are so rare during the child-bearing years. This risk is also small when com­pared with the usual risks of preg­nancy. Overall, the benefits of the pill usually overwhelm the small increased risk of a stroke.

• Hormone replacement therapy:

Unfortunately, hormone replacement therapy (HRT) can cause simi­lar problems to the contraceptive pill, with large clinical trials demonstrat­ing the risks and benefits of treat­ment. The combined use of oestrogen and progesterone (for women with a uterus) and the use of oestrogen alone (for women who have had a hysterectomy) are both associated with a small increase in the risk of stroke. HRT can carry additional risks (for example, pulmonary embolism) but also some benefits (for example, a reduction in bone fractures), so this subject is complicated and needs careful discussion with a doctor.

• Illegal drugs:

Recreational drugs, such as cocaine or Ecstasy, or drugs used to enhance sports performance illegally can cause strokes in younger people. Unfor­tunately, an increasing number of drug-associated strokes are occur­ring and these are clearly avoidable disasters.

• Migraine:

Migraine is very com­mon but still poorly understood. The symptoms of flashing lights and spreading abnormal sensations affecting the arms, face or legs are very common. Occasionally, these attacks can also be associated with temporary weakness. Very rarely, the migraine attack leaves a more permanent physical weakness called a migrainous stroke.

• Rare inherited forms of strokes:

Sometimes, a stroke in young adulthood may be caused by genetic problems, and one syndrome has recently been shown to run in families. It is very rare and causes multiple strokes. The syndrome has the name cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy or CADASIL for short.