A stroke is a serious medical condition that occurs when the blood supply to part of the brain is cut off.
Strokes are a medical emergency and prompt treatment is essential because the sooner a person receives treatment for a stroke, the less damage is likely to happen.
If you suspect that you or someone else is having a stroke, phone immediately for an ambulance.
Read more about the symptoms of a stroke.
Why do strokes happen?
Like all organs, the brain needs the oxygen and nutrients provided by blood to function properly. If the supply of blood is restricted or stopped, brain cells begin to die. This can lead to brain damage and possibly death.
Types of stroke
There are two main types of stroke:
- ischaemic (accounting for over 80% of all cases) – the blood supply is stopped due to a blood clot
- haemorrhagic – a weakened blood vessel supplying the brain bursts and causes brain damage
There is also a related condition known as a transient ischaemic attack (TIA), where the supply of blood to the brain is temporarily interrupted, causing a 'mini-stroke'. TIAs should be treated seriously as they are often a warning sign that a stroke is coming.
Who is at risk from stroke?
People over 65 years of age are most at risk from having strokes, although 25% of strokes occur in people who are under 65. It's also possible for children to have strokes.
If you're south Asian, African or Caribbean, your risk of stroke is higher. This is partly because of a predisposition (a natural tendency) to developing diabetes and heart disease, which are two conditions that can cause strokes.
Smoking, being overweight, lack of exercise and a poor diet are also risk factors for stroke. Also, conditions that affect the circulation of the blood, such as high blood pressure, high cholesterol, atrial fibrillation (an irregular heartbeat) and diabetes, increase your risk of having a stroke.
Read more about the causes of stroke.
Treating a stroke
Treatment depends on the type of stroke you have, including which part of the brain was affected and what caused it.
Most often, strokes are treated with medicines. This generally includes drugs to prevent and remove blood clots, reduce blood pressure and reduce cholesterol levels.
In some cases, surgery may be required. This is to clear fatty deposits in your arteries or to repair the damage caused by a haemorrhagic stroke.
Read more about treating stroke.
Life after a stroke
The damage caused by a stroke can be widespread and long-lasting. Some people need to have a long period of rehabilitation before they can recover their former independence, while many will never fully recover.
The process of rehabilitation will be specific to you, and will depend on your symptoms and how severe they are. A team of specialists are available to help, including physiotherapists, psychologists, occupational therapists, speech therapists and specialist nurses and doctors.
The damage that a stroke causes to your brain can impact many aspects of your life and wellbeing, and depending on your individual circumstances, you may require a number of different treatment and rehabilitation methods.
Read more about recovering from a stroke.
Can strokes be prevented?
Strokes can usually be prevented through a healthy lifestyle. Eating a healthy diet, taking regular exercise, drinking alcohol in moderation and not smoking will dramatically reduce your risk of having a stroke. Lowering high blood pressure and cholesterol levels with medication also lowers the risk of stroke substantially.
Read more about preventing stroke.
If you suspect you or someone else is having a stroke, phone immediately for an ambulance.
Even if the symptoms of a stroke disappear while you're waiting for the ambulance to arrive, you or the person having the stroke should still go to hospital for an assessment. Symptoms that disappear may mean you have had a transient ischaemic attack (TIA) and you could be at risk of having a full stroke at a later stage.
After an initial assessment, you may need to be admitted to hospital to receive a more in-depth assessment and, if necessary, for specialist treatment to begin.
Recognising the signs and symptoms of a stroke
The signs and symptoms of a stroke vary from person to person but usually begin suddenly. As different parts of your brain control different parts of your body, your symptoms will depend upon the part of your brain affected and the extent of the damage.
The main stroke symptoms can be remembered with the word FAST: Face-Arms-Speech-Time.
- Face – the face may have dropped on one side, the person may not be able to smile or their mouth or eye may have drooped
- Arms – the person with suspected stroke may not be able to lift one or both arms and keep them there because of arm weakness or numbness
- Speech – their speech may be slurred or garbled, or the person may not be able to talk at all despite appearing to be awake
- Time – it's time to call an ambulance immediately if you see any of these signs or symptoms
It's important for everyone to be aware of these signs and symptoms. If you live with or care for somebody in a high-risk group, such as someone who is elderly or has diabetes or high blood pressure, being aware of the symptoms is even more important.
Symptoms in the FAST test identify about nine out of 10 strokes.
Other signs and symptoms may include:
- numbness or weakness resulting in complete paralysis of one side of the body
- sudden loss of vision
- communication problems, difficulty talking and understanding what others are saying
- problems with balance and coordination
- difficulty swallowing
- sudden and severe headache, unlike any the person has had before, especially if associated with neck stiffness
- blacking out (in severe cases)
'Mini-stroke' or transient ischaemic attack (TIA)
The symptoms of a transient ischaemic attack (TIA) are the same as a stroke, last from between a few minutes to a few hours, then completely disappear. However, never ignore a TIA as it's a serious warning sign there is a problem with the blood supply to your brain.
There is about a 1 in 10 chance those who have a TIA will experience a full stroke during the four weeks following the TIA. If you have had a TIA, you should contact your doctor, local hospital or out-of-hours service, as soon as possible.
Stroke is a largely preventable condition. Many risks can be reduced by making lifestyle changes. However, some things that increase the risk of stroke cannot be changed, including:
- age – you're more likely to have a stroke if you're over 65 years old, although about a quarter of strokes happen in younger people
- family history– if a close relative (parent, grandparent, brother or sister) has had a stroke, your risk is likely to be higher
- ethnicity – if you're south Asian, African or Caribbean, your risk of stroke is higher, partly because rates of diabetes and high blood pressure are higher in these groups
- your medical history – if you have previously had a stroke, TIA or heart attack, your risk of stroke is higher
Ischaemic strokes, the most common type of stroke, occur when blood clots block the flow of blood to the brain. Blood clots typically form in areas where the arteries have been narrowed or blocked by fatty cholesterol-containing deposits known as plaques. This narrowing of the arteries is caused by atherosclerosis. As we get older our arteries become narrower, but certain things can dangerously accelerate the process. These risks include:
- high blood pressure (hypertension)
- high cholesterol levels (often caused by a high-fat diet, but can result from inherited factors)
- a family history of heart disease or diabetes
- excessive alcohol intake (which can also make obesity and high blood pressure worse, as well as causing heart damage and an irregular heartbeat)
Diabetes is also a risk factor, particularly if poorly controlled, as the excess glucose in the blood can damage the arteries. Another possible cause of ischaemic stroke is an irregular heartbeat (atrial fibrillation), which can cause blood clots that become lodged in the brain. Atrial fibrillation can be caused by:
- high blood pressure
- coronary artery disease
- mitral valve disease (disease of the heart valve)
- cardiomyopathy (wasting of the heart muscle)
- pericarditis (inflammation of the bag surrounding the heart)
- hyperthyroidism (overactive thyroid gland)
- excessive alcohol intake
- drinking lots of caffeine; for example, tea, coffee and energy drinks
Haemorrhagic strokes (also known as cerebral haemorrhages or intracranial haemorrhages) usually occur when a blood vessel in the brain bursts and bleeds into the brain (intracerebral haemorrhage). In about 5% of cases, the bleeding occurs on the surface of the brain (subarachnoid haemorrhage). The main cause of haemorrhagic stroke is high blood pressure (hypertension), which can weaken the arteries in the brain and make them prone to split or rupture. Things that increase the risk of high blood pressure include:
- being overweight or obese
- drinking excessive amounts of alcohol
- a lack of exercise
- stress, which may cause a temporary rise in blood pressure
Another important risk of haemorrhagic stroke is treatment with medicines given to prevent blood clots, such as warfarin. Haemorrhagic stroke can also occur from the rupture of a balloon-like expansion of a blood vessel (aneurysm) and badly-formed blood vessels in the brain. A traumatic head injury can also cause bleeding into the brain. In most cases, the cause is obvious, but bleeding into the lining of the brain (subdural haematoma) can occur without any obvious signs of trauma, especially in the elderly. The symptoms and signs can then mimic a stroke.
Strokes are usually diagnosed by studying images of the brain (brain imaging) and carrying out physical tests.
Your doctor may check for the causes of your stroke by taking blood tests to determine your cholesterol and blood sugar levels, checking your pulse for an irregular heartbeat and taking a blood pressure measurement.
Even if the physical symptoms of a stroke are obvious, brain imaging should also be carried out to determine:
- if the stroke has been caused by a blocked artery or burst blood vessel
- which part of the brain has been affected
- how severe the stroke is
- the risk of a transient ischaemic attack (TIA)
Different treatment is required for each type of stroke so a rapid diagnosis will make treatment more straightforward.
CT and MRI scans
A CT scan is like an X-ray, but uses multiple images to build up a more detailed, three-dimensional (3D) picture of your brain. An MRI scan uses a strong magnetic field and radio waves to produce a detailed picture of the inside of your body.
The type of scan you may have in hospital depends on your symptoms. If it's suspected you had a major stroke, a CT scan is sufficient to identify whether the stroke is due to bleeding or clotting. It's quicker than an MRI scan and improves the chances of rapidly delivering treatments such as clot-busting drugs (thrombolysis) that might be used in appropriate cases, but are time-limited and require the results of the scan before the treatment can be given safely.
For people with more complex symptoms, where the extent or location of the damage is unknown, and in patients who have recovered from a transient ischaemic attack, an MRI scan is more appropriate. This will provide greater detail of brain tissue, allowing smaller, or more unusually located strokes to be identified.
All patients with suspected stroke should receive a brain scan within 24 hours. Some patients should be scanned within the hour, especially those who:
- might benefit from clot-busting drugs (thrombolysis) such as alteplase or early anticoagulant treatment
- are already on anticoagulant treatments
- have a lower level of consciousness
After the injection of a dye into an arm vein, both CT and MRI can be used to take pictures of the blood vessels in the brain, as well as the blood vessels in the neck that take blood to the brain from the heart. This is known as CT or MR angiography and is often done immediately after taking pictures of the brain itself.
A swallow test is essential for anybody who's had a stroke.
Swallowing problems affect over a third of people after a stroke. When a person cannot swallow properly, there's a risk food and drink may get into the windpipe and then into the lungs (called aspiration), which can lead to chest infections and pneumonia.
The test is simple. The person is given a few teaspoons of water to drink. If they can swallow this without choking and coughing they will be asked to swallow half a glass of water.
If they have any difficulty swallowing, they will be referred to a speech and language therapist for a more detailed assessment. They will usually be kept ‘nil by mouth’ until they have seen the therapist and may therefore need to have fluids or food given directly into an arm vein (intravenous drip) or through the nose using a nasogastric tube.
Heart and blood vessel tests
Further tests on the heart and blood vessels might be carried out later to confirm what caused the stroke. These may include:
Ultrasound (carotid ultrasonography)
An ultrasound scan uses high-frequency sound waves to produce an image of the inside of your body. Your doctor may use a wand-like probe (transducer) to send high-frequency sound waves into your neck. These pass through the tissue creating images on a screen that will show if there's any narrowing or clotting in the arteries leading to your brain.
This type of ultrasound scan is sometimes known as a doppler scan or a duplex scan. Where carotid ultrasonography is needed, it should happen within 48 hours.
Catheter angiography (arteriography)
Dye is injected into your carotid or vertebral artery via a tube called a catheter. This gives a more detailed view of your arteries than can be obtained using ultrasound, CT angiography or MR angiography.
In some cases, an echocardiogram may be used to produce images of your heart using an ultrasound probe placed on your chest (transthoracic echocardiogram). In addition, transoesophageal echocardiography (TOE) may also be used. This involves an ultrasonic probe that's passed down the food pipe (oesophagus), usually under sedation. Because it's directly behind the heart, it produces a clear image of blood clots and other abnormalities that may not get picked up by the transthoracic echocardiogram.
Ischaemic strokes can be treated using a 'clot-busting' medicine called alteplase, which dissolves blood clots (thrombolysis). However, alteplase is only effective if started during the first four and a half hours after the onset of the stroke. After that time, the medicine has not been shown to have beneficial effects. Even within this narrow time frame, the quicker alteplase can be started the better the chance of recovery. However, not all patients are suitable for thrombolysis treatment.
You'll also be given a regular dose of aspirin (an antiplatelet medication), as this makes the cells in your blood, known as platelets, less sticky, reducing the chances of further blood clots occurring. If you're allergic to aspirin, other antiplatelet medicines are available.
You may also be given an additional medication called an anticoagulant. Like aspirin, anticoagulants prevent blood clots by changing the chemical composition of the blood in a way that prevents clots from occurring. Heparin, warfarin and more recently rivaroxaban are examples of anticoagulants.
Anticoagulants are often prescribed for people who have an irregular heartbeat that can cause blood clots.
If your blood pressure is too high, you may be given medicines to lower it. Medicines that are commonly used include:
- thiazide diuretics
- angiotensin-converting enzyme (ACE) inhibitors
- calcium channel blockers
Read more about treating high blood pressure.
If the level of cholesterol in your blood is too high, you will be given a medicine known as a statin. Statins reduce the level of cholesterol in your blood by blocking an enzyme (chemical) in the liver that produces cholesterol.
Some ischaemic strokes are caused by a narrowing in the carotid artery, which is an artery in the neck, which takes blood to the brain. The narrowing, known as carotid stenosis, is caused by a build-up of fatty plaques.
If the carotid stenosis is particularly bad, surgery may be used to unblock the artery. This is done using a surgical technique called a carotid endarterectomy. It involves the surgeon making an incision in your neck in order to open up the carotid artery and remove the fatty deposits.
Emergency surgery is often needed to treat haemorrhagic strokes to remove any blood from the brain and repair any burst blood vessels. This is usually done using a surgical procedure known as a craniotomy.
During a craniotomy, a small section of the skull is cut away to allow the surgeon access to the cause of the bleeding. The surgeon will repair any damaged blood vessels and ensure there are no blood clots present that may restrict the blood flow to the brain. After the bleeding has been stopped, the piece of bone removed from the skull is replaced.
Following a craniotomy, the patient may have to be placed on a ventilator. A ventilator is a machine that assists someone with their breathing. It gives the body time to recover by taking over its normal responsibilities, such as breathing, and it will help control any swelling in the brain.
The patient will also be given medicines, such as ACE inhibitors, to lower blood pressure and prevent further strokes from occurring.
Transient ischaemic attack (TIA)
The treatment for a TIA involves addressing the risk factors that may have led to it, to try to prevent a bigger, more serious stroke.
If you have a TIA, the treatment you receive will depend on what caused it, but you will typically be given one of the medicines outlined above or a combination of them. So, if high blood pressure and high cholesterol levels put you at risk of having a stroke, you may be given a combination of statins and ACE inhibitors.
If the risk of a stroke is high due to a build-up of fatty plaques in your carotid artery, a carotid endarterectomy may be required.
A poor diet is a major risk factor for a stroke. High-fat foods can lead to the build-up of fatty plaques in your arteries and being overweight can lead to high blood pressure.
A low-fat, high-fibre diet is recommended, including plenty of fresh fruit and vegetables (five portions a day) and whole grains. You should limit the amount of salt you eat to no more than 6g (0.2oz) a day because too much salt will increase your blood pressure. 6 grams of salt is about one teaspoonful.
There are two types of fat – saturated and unsaturated. You should avoid food containing saturated fats because these will increase your cholesterol levels.
Foods high in saturated fat include:
- meat pies
- sausages and fatty cuts of meat
- ghee – a type of butter often used in Indian cooking
- hard cheese
- cakes and biscuits
- foods that contain coconut or palm oil.
However, a balanced diet should include a small amount of unsaturated fat, which will help reduce your cholesterol levels.
Foods high in unsaturated fat include:
- oily fish
- nuts and seeds
- sunflower, rapeseed, olive and vegetable oils
Combining a healthy diet with regular exercise is the best way to maintain a healthy weight. Having a healthy weight reduces your chances of developing high blood pressure.
Regular exercise will make your heart and blood circulatory system more efficient. It will also lower your cholesterol level and keep your blood pressure at a healthy level.
For most people, at least 150 minutes (2 hours and 30 minutes) of moderate-intensity aerobic activity (i.e. cycling or fast walking) every week is recommended.
If you're recovering from a stroke, you should discuss possible exercise plans with the members of your rehabilitation team. Regular exercise may be impossible in the first weeks or months following a stroke but you should be able to begin exercising once your rehabilitation has progressed.
Smoking doubles your risk of having a stroke. This is because it narrows your arteries and makes your blood more likely to clot.
If you stop smoking, you can reduce your risk of having a stroke by up to half. Not smoking will also improve your general health and reduce your risk of developing other serious conditions, such as lung cancer and heart disease.
Excessive alcohol consumption can lead to high blood pressure and an irregular heartbeat (atrial fibrillation). Both are major risk factors for stroke.
Because alcoholic drinks are rich in energy (high in calories) they also cause weight gain. Heavy drinking multiplies the risk of stroke by more than 3 times.
The 2 most common psychological conditions found in people after a stroke are:
- depression – many people experience intense bouts of crying and feel hopeless and withdrawn from social activities
- anxiety disorder – where people experience general feelings of fear and anxiety, often punctuated by intense, uncontrolled feelings of anxiety (anxiety attack)
You'll receive a psychological assessment from a member of your healthcare team within the first month after your stroke.
Feelings of anger, anxiety, depression, frustration and bewilderment are all common, although they may fade over time. Your healthcare team, family, friends and organisations can all provide you with the support and care you need.
Advice should be given to help deal with the psychological impact of stroke. This includes the impact on relationships with other family members and any sexual relationship. There should also be a regular review of any problems of depression and anxiety, and psychological and emotional symptoms generally.
These symptoms tend to settle down over time but if symptoms are severe or last a long time, doctors can refer people for expert healthcare from a psychiatrist or clinical psychologist. For some people, medicines and psychological therapies, such as counselling or cognitive behavioural therapy (CBT) can help. CBT is a therapy that aims to change the way you think about things in order to produce a more positive state of mind.
Cognitive is a term used by scientists to describe the many processes and functions our brain uses to process information.
1 or more cognitive functions can be disrupted by a stroke. Cognitive functions include:
- communication – both verbal and written
- spatial awareness – having a natural awareness of where your body is in relation to your immediate environment
- executive function – the ability to plan, solve problems and reason about situations
- praxis – the ability to carry out skilled physical activities, such as getting dressed or making a cup of tea
As part of your treatment, each one of your cognitive functions will be assessed and a treatment and rehabilitation plan will be created.
You can be taught a wide range of techniques that can help you re-learn disrupted cognitive functions, such as recovering communication skills through speech therapy.
There are also many methods to compensate for any loss of cognitive function, such as using memory aids or a wall planner to help plan daily tasks.
Most cognitive functions will return after time and rehabilitation, but you may find they don't return to their former levels.
The damage that a stroke causes to your brain also increases the risk of developing vascular dementia. Dementia may happen immediately after a stroke or may develop some time after the stroke occurred.
Strokes can cause weakness or paralysis in one side of the body. Also, many people have problems with coordination and balance. Many people suffer from extreme tiredness (fatigue) in the first few weeks after a stroke, and may also have difficulty sleeping, making them even more tired.
As part of your rehabilitation, you should be seen by a physiotherapist, who will assess the extent of any physical disability before drawing up a treatment plan.
Physiotherapy will normally begin as soon as your medical condition has stabilised. At first, your physiotherapist will work with you to improve your posture and balance.
After this, you'll have short sessions of physiotherapy that last a few minutes. The sessions will then increase in duration as you start to regain muscle strength and control.
The physiotherapist will work with you by setting goals. At first, these may be simple goals like picking up an object. As your condition improves, more demanding long-term goals, such as standing or walking, will be set.
A care worker or carer, such as a member of your family, will be encouraged to become involved in your physiotherapy. The physiotherapist can teach you both simple exercises you can carry out at home.
Sometimes, physiotherapy can last months or even years. The treatment is stopped when it's no longer producing any marked improvement to your condition.
After having a stroke, many people experience problems with speaking and understanding, as well as with reading and writing. This is called aphasia and sometimes also known as dysphasia.
Aphasia can be caused by damage to the parts of the brain responsible for language, or be due to muscles involved in speech being affected. You should see a speech and language therapist as soon as possible for an assessment, and to start therapy to help you with communication skills.
Stroke can sometimes damage the parts of the brain that receive, process and interpret information sent by the eyes. Some people may have double vision, or lose half of their field of vision in one eye. This means they're able to see everything on one side of the eye, but are blind on the other side.
Sex after stroke
Even if you've been left with a severe disability, it's important to experiment with different positions and find new ways of being intimate with your partner. Having sex will not put you at a higher risk of having a stroke. There's no guarantee you will not have another stroke but there's no reason why it should happen while you're having sex.
Be aware that some drugs can reduce your sex drive (libido), so make sure your doctor knows if you have a problem, there may be other medicines that can help.
Bladder and bowel control
Some strokes damage the part of the brain that controls bladder and bowel movements. This can result in urinary incontinence and difficulty with bowel control.
Most people who've had a stroke regain control in a week or so. If there are still problems when they leave hospital after a stroke, there is help available from the hospital, your doctor or acommunity continence nurse.
If you've had a stroke, you can't drive for 1 month. Whether you can return to driving depends on what long-term disabilities you may have and the type of vehicle you drive.
Your doctor can advise about whether you can start driving again a month after your stroke or whether you need further assessment at a mobility centre.
Caring for someone
There are many ways you can provide support to a friend or relative who has had a stroke to speed up their rehabilitation process. These include:
- helping them practice physiotherapy exercises in between their sessions with the physiotherapist
- providing emotional support and reassurance that their condition will improve with time
- helping motivate the person to reach their long-term goals
- adapting to any needs they may have, such as speaking slowly if they have communication problems
Caring for somebody after a stroke can be a frustrating and sometimes lonely experience. The advice outlined below may help.
Be prepared for changed behaviour
Someone who has had a stroke can often seem as though they have had a change in personality and appear to act irrationally at times. This is due to the psychological and cognitive impact of a stroke. They may become angry or resentful towards you. Upsetting as it may be, try not to take it personally. It's important to remember that a person will return to their old self as their rehabilitation progresses.
Try to remain patient and positive
Rehabilitation can be a slow and frustrating process, and there will be periods of time when it appears little progress has been made. Encouraging and praising any progress, no matter how small it may appear, can help motivate someone who has had a stroke to achieve their long-term goals.
Make time for yourself
If you're caring for someone who's had a stroke, it's important not to neglect your own physical and psychological wellbeing. Socialising with friends or pursuing leisure interests will help you cope better with the situation.
Ask for help
There's a wide range of support services and resources available for people recovering from strokes, and their families and carers. This ranges from equipment that can help with mobility, to psychological support for carers and families.
The hospital staff involved with the rehabilitation process can provide advice and relevant contact information.
Will I be able to lead a normal life again?
- A third of people will make an almost full recovery physically and should be encouraged to lead a normal life.
- A third of people will have a significant amount of disability. This will vary from the severely disabled, e.g. people who need help getting in and out of bed, to milder things, such as needing help with bathing.
- A third of people will be severely affected by stroke and will die within the year. The majority of these people will die in hospital in the first few weeks.
There are complications that can arise as a result of a stroke, many of which are potentially life-threatening.
The damage caused by a stroke can interrupt your normal swallowing reflex, making it possible for small particles of food to enter your respiratory tract (windpipe).
To prevent any complications from dysphagia, you may be fed using a feeding tube. The tube is usually put into your nose and then passed into your stomach, but it may be directly connected to your stomach during surgery.
How long you will need a feeding tube can vary from a few weeks to a few months, but it's rare to have to use a tube for more than six months.
Hydrocephalus is a condition that occurs when there's too much cerebrospinal fluid (CSF) in the cavities (ventricles) of the brain. About 10% of people who experience a haemorrhagic stroke will develop hydrocephalus.
CSF is produced in the brain to protect it and the spinal cord and carry away waste from brain cells. It flows continuously through the ventricles and over the surface of the brain and spinal cord. Any excess CSF usually drains away from the brain and is absorbed by the body.
Damage caused by a haemorrhagic stroke can stop the CSF from draining, and an excess of fluid can build up. Symptoms include:
- sickness and vomiting
- loss of balance
However, the condition can be treated by placing a tube into the brain to allow the fluid to drain properly.
Deep vein thrombosis
Around 5% of people who have had a stroke will experience a further blood clot in their leg, known as deep vein thrombosis (DVT).
This normally occurs in people who have lost some or all of the movement in their leg, as immobility will slow the blood flow in their veins, increasing blood pressure and the chances of a blood clot.
Symptoms of DVT include:
- warm skin
- redness, particularly at the back of the leg, below the knee
If you have DVT, prompt treatment is required because there's a chance the clot may move into your lungs, which is known as a pulmonary embolism and can be fatal.
DVT can be treated using anti-clotting medicines. If it's felt that you're at risk of DVT, your stroke team may recommend you wear a compression stocking. This is a specially designed stocking that can reduce the blood pressure in your legs.