Stroke - Diagnosing stroke

Strokes are usually diagnosed by carrying out physical tests and studying images of the brain produced during a scan.

When you first arrive at hospital with a suspected stroke, a doctor will usually want to find out as much as they can about your symptoms.

A number of tests can then be carried out to help confirm the diagnosis and determine the cause of the stroke.

This may include blood tests to determine your cholesterol and blood sugar levels, checking your pulse for an irregular heartbeat and taking a blood pressure measurement.

Brain scans

Even if the physical symptoms of a stroke are obvious, brain scans should also be carried out to determine:

• if the stroke has been caused by a blocked artery (ischaemic stroke) or burst blood vessel (haemorrhagic stroke)
• which part of the brain has been affected
• how severe the stroke is

Different treatment is required for the different types of stroke, so a rapid diagnosis will make treatment more straightforward.

Everyone with suspected stroke should receive a brain scan within 24 hours and some people should be scanned within an hour of the onset of symptoms, 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

This is why a stroke is a medical emergency and why 999 should be dialled when a stroke is suspected – there isn’t time to wait for a GP appointment.

The two main types of scan used to assess the brain in people who have had a suspected stroke are a computerised tomography (CT) scan and a magnetic resonance imaging (MRI) scan. The type of scan you may have largely depends on your symptoms.

CT scans

A CT scan is like an X-ray, but uses multiple images to build up a more detailed, three-dimensional picture of your brain to help your doctor identify any problem areas.

During the scan, you may be given an injection of a special dye into one of the veins in your arm to help improve the clarity of the CT image and look at the blood vessels that supply the brain.

If it is suspected you are experiencing a major stroke, a CT scan is usually able to show whether you have had an ischaemic stroke or a haemorrhagic stroke. It's generally quicker than an MRI scan and can mean you are able to receive appropriate treatment sooner.

MRI scans

An MRI scan uses a strong magnetic field and radio waves to produce a detailed picture of the inside of your body.

For people with more complex symptoms, where the extent or location of the damage is unknown – and in people who have recovered from a transient ischaemic attack (TIA) – an MRI scan is more appropriate. This will provide greater detail of brain tissue, allowing smaller, or more unusually located areas affected by a stroke to be identified.

As with a CT scan, special dye can be used to improve MRI scan images.

Swallow tests

A swallow test is essential for anybody who has had a stroke, as swallowing ability is commonly affected early after a stroke.

When a person cannot swallow properly, there is a risk that food and drink may get into the windpipe and then into the lungs (called aspiration), which can lead to chest infections such as 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 the speech and language therapist for a more detailed assessment.

They will usually not be allowed to eat or drink normally until they have seen the therapist and may therefore need to have fluids or food given directly into an arm vein (intravenously) or through a tube inserted into their stomach via their nose.

Heart and blood vessel tests 

Further tests on the heart and blood vessels might be carried out later to confirm what caused your stroke. Some of the tests that may be carried out are described below.

Carotid ultrasound

A carotid ultrasound scan can help show if there is any narrowing or blockages in the neck arteries leading to your brain.

An ultrasound scan involves using a small probe (transducer) to send high-frequency sound waves into your body. When these sound waves bounce back, they can be used to create an image of the inside of your body.

When carotid ultrasonography is needed, it should happen within 48 hours.

Echocardiography

In some cases another type of ultrasound scan called an echocardiogram may be carried out to produce images of your heart and check for any problem with it that could be related to your stroke.

This will normally involve using an ultrasound probe moved across your chest (transthoracic echocardiogram).

In some cases, an alternative type of echocardiogram called transoesophageal echocardiography (TOE) may also be used.

This involves passing an ultrasound probe down your gullet (oesophagus), usually under sedation. As this allows the probe to be placed directly behind the heart, it produces a clear image of blood clots and other abnormalities that may not get picked up by a transthoracic echocardiogram.