NSE : Information on epilepsy: Diagnosing epilepsy, finding out the causes of seizures, epilepsy tests

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Information on epilepsy: Diagnosing epilepsy

How epilepsy is diagnosed

A person is diagnosed as having epilepsy if they have had two or more seizures that started in the brain. However, getting a diagnosis of epilepsy can be very difficult because there is no single test that can
diagnose epilepsy.

Diagnosing epilepsy involves collecting information from different tests, talking to the person about what has been happening to them, and speaking to anyone else who might have seen the seizures. With all the
collected information the most likely cause of the seizures may be found.

This leaflet looks at how epilepsy is diagnosed. It explains the tests that are usually done and what these tests might show about the seizures the person is having.

What are epileptic seizures?

There are many causes for seizures, but epileptic seizures are all caused by interrupted brain signals. The brain is made up of millions of nerve cells which control how we think, move and feel. The nerve cells
do this by passing electrical signals to each other. In some people these signals may suddenly be interrupted and this can cause an epileptic seizure (sometimes called a ‘fit’ or ‘attack’). When someone has a seizure it is a symptom that the way their brain is working is interrupted.

The brain has many different functions. Personality, mood, memory, movement, consciousness and our senses are all controlled by the brain. These can all be affected if a person has an epileptic seizure.
Epileptic seizures can look different from person to person.

More information on seizures.
More information on epilepsy.

What is epilepsy?

Epilepsy is the tendency to have seizures that start in the brain. To be given a diagnosis of epilepsy you must have had:
• two or more seizures; and
• these seizures must have started in the brain.

Anyone can have a single epileptic seizure at some point in their life. This is why a diagnosis of epilepsy is usually only considered when a person has had more
than one seizure. However, if you have had only one seizure your doctor may still wish to consider what may have caused it, especially if they think it might be something other than epilepsy, for example seizures caused by other conditions such as diabetes.

How is epilepsy diagnosed?

If there is a possibility that you have epilepsy, your GP may refer you to a neurologist. A neurologist is a doctor who specialises in conditions affecting the brain and nervous system, such as epilepsy.

Much of the diagnosis of epilepsy is based on finding out what happened to you before, during and after the seizures.

Apart from the description, there are other things that can help to explain why the seizures have happened. Your medical history and any other medical conditions will also be considered as part of the diagnosis.

What happened during the seizure?

Finding out what happened before, during and after a suspected seizure can often tell a lot about why it might have happened. For example, some types of faints can look like certain epileptic seizures. But often before fainting a person feels cold, clammy and
their vision goes blurry. Whereas epileptic seizures often happen very suddenly and the person may have no warning that a seizure is about to happen.

How you felt afterwards can also help to explain what happened. For example, when someone comes around after an epileptic seizure, they may feel confused, very tired and may want to sleep.

The person who had the seizure may not remember much, if anything, about it. This might be because they were unconscious at the time or very confused
afterwards.

If you see someone having a seizure here are some questions that can help you give useful information about what happened.

• Where was the person and what were they doing before the seizure?

• Did you notice their mood change - were they excited, anxious or quiet?

• Were there any triggers for the seizure– did they feel tired, hungry, or unwell?

• Did they have any warning that the seizure was going to happen?

• Did they have any unusual sensations, such as an odd smell or taste?

• What made you notice the seizure – a noise, did they fall, or did their eyes roll?

• Did they appear to be ‘blank’ or stare into space?

• Did they lose consciousness or were they confused?

• Did they do anything unusual such as mumble, wander about or fiddle with their clothing?

• Did their colour change (become pale or flushed) and if so, where (face or lips)?

• Did their breathing change (e.g. become noisy or look difficult)?

• Did any part of their body move, jerk or twitch?

• Did they fall down, or go stiff or floppy?

• Did they wet themselves?

• Did they bite their tongue or cheek?

• How long did the seizure last?

• What were they like after the seizure– did they need to sleep?

• How long was it before they were able to carry on as normal?

• Did you notice anything else?

Looking at the medical history

Sometimes the cause of someone’s epilepsy can be found. For example, someone might develop epilepsy after they have had a head injury, brain infection (such as meningitis) or stroke. Or there may be a genetic cause (passed from parent to child) for their epilepsy - some inherited conditions, such as tuberous sclerosis, can cause epilepsy.

Finding out more about your medical history can sometimes help to find a reason why seizures have started.

For most people there are no clear reasons why they have epilepsy.

What tests might I have?

Your neurologist may ask you to have some tests to get extra information about the seizures. The tests are usually done by a technician (a person who is trained to do them). The results from the tests are then
passed back to the neurologist to see what they show. The results may indicate that you have epilepsy and may also say why you have epilepsy.

You may not need to have all of the tests mentioned in this leaflet, but the following information explains what the tests are, why they are done and what they might say about the seizures you are having.

Tests to rule out other causes

There are many different causes of seizures and some causes can easily be mistaken for epilepsy. Although seizures with different causes may look similar to epileptic seizures there are often subtle differences which help your doctor to make the correct diagnosis.There are a number of tests that can help
rule out other causes. These include the following tests.

Blood tests

To do a blood test, a sample of blood is taken, usually from your arm, with a syringe. The sample is used to check your general health. The test is also used to rule out other possible causes of the seizures, such as low blood sugar levels or diabetes.

Electrocardiogram (ECG)

An ECG is used to record the electrical activity of the heart. This is done by sticking electrodes (a bit like plasters) to the arms, legs and chest. These electrodes pick up the electrical signals from the heart.

Because an ECG does not give out electrical signals,
having one doesn’t hurt. An ECG can help to rule out the seizure being caused by the way the heart is working.

Tests to diagnose epilepsy

No test can say for certain whether you do or do not have epilepsy. But when the information from the tests is added to the other information about what happens during the seizures, this builds up a clearer picture
of what happened. This may help with the diagnosis and when choosing treatment.

Electroencephalograms (EEG)

An EEG is used to record the electrical activity of the brain by picking up the electrical signals from the brain cells. These signals are picked up by electrodes on the head and are recorded on paper or on a
computer.

The recording shows how the brain is working. Like the ECG, the electrodes only record electrical activity - they do not give out electrical signals and they do not hurt.

Before the test, the technician places the small electrodes on your head – the electrodes are held in place with a sticky paste. The electrodes are connected to the recording machine. The test lasts about 30 minutes and you will probably be sitting or
lying down

More information on EEG

What does an EEG show?

An EEG gives information about the electrical activity of the brain during the time the test is happening. When someone has an epileptic seizure their brain activity changes. This change can sometimes be seen on an EEG recording - it is often called epileptiform
activity. Some people can have epileptiform activity even when they are not having a seizure, so an EEG can be particularly useful for them.

Epileptiform activity can sometimes be provoked by deep breathing. The test may include deep breathing to see if epileptiform activity can be provoked and recorded.

Your results

An EEG test can usually show if someone is having a seizure at the time of the test, but it can’t show what happens in the person’s brain at any other time. So even though your test results might not show any unusual activity it does not completely rule out having
epilepsy. Some types of epilepsy are very difficult to identify with an EEG test.

Some people who do not have epilepsy can sometimes have irregular activity on their EEG. But a result where there is irregular activity does not necessarily mean that the person has epilepsy.

Flashing lights during the EEG

Some people with epilepsy have seizures that are started, or ‘triggered’, by flashing lights. This is called photosensitive epilepsy.

An EEG test will usually include testing for photosensitive epilepsy. You will be asked to look at a light which will flash at different speeds. If this causes any changes in your brain activity the technician can stop the flashing light before a seizure develops.

Sleep-deprived EEG

For some people there is more chance of irregular brain activity happening when they are tired or when they are going to sleep. If this is the case for you, having a sleepdeprived EEG might help get a more useful reading. This test is done in the same way
as a normal EEG but you sleep during the test. To help you sleep, you may be asked to stay awake some, or all, of the night before. In some cases you may be given a mild sedative to help you get to sleep.

Ambulatory EEG

An ambulatory EEG works in the same way as a normal EEG but is portable. It is a small machine that is worn on a belt around your waist. Because it is portable you can move around and carry on with your normal day-to-day routine while the recording happens.

This type of EEG allows brain activity to be recorded for several hours, days or weeks. Because the brain activity is recorded for longer, there is more chance of a seizure being recorded on the EEG than during the
normal 30 minute test.

Video telemetry

Video telemetry testing happens in hospital, usually over a couple of days. During your stay you have your own room. In the room, often mounted on the wall, there is a video camera that records what you are doing. At the same time you will wear a portable EEG
so that you are able to move around your room. Being videoed whilst wearing an EEG means that if you have a seizure your doctor can compare the electrical activity of your brain with what is happening to your body.

The results can help identify what types of seizure you are having, and the most appropriate way of treating them.

Brain scans

Brain scans can be used to help find the cause of someone’s seizures. The scans produce pictures of the brain which might show a physical cause for epilepsy, such as scarring on the brain. But for many people a brain scan does not show up a cause for
their seizures, and even if nothing unusual is seen, the person may still have epilepsy.

The two common types of brain scan are Magnetic Resonance Imaging and Computerised Axial Tomography.

Magnetic resonance imaging (MRI scan)
MRI scans use magnetic fields to create pictures of the brain.
More information on MRI

Computerised axial tomography (CT or CAT scan)
CT scans use X-rays to take images of the brain. CT scans are not suitable if you are pregnant because of the X-rays. During a CT scan you lie on a couch which slides into the scanner.

Unlike MRI scanners, CT scanners do not make a loud noise. The pictures from a CT scan are often less detailed than from MRI scans.

Treating seizures

If a diagnosis of epilepsy is made, your neurologist will talk to you about starting treatment. Epilepsy is usually treated with anti-epileptic drugs (AEDs). AEDs aim to prevent seizures from happening but don’t
cure epilepsy. Up to 70% of people with epilepsy could have their seizures completely stopped with AEDs.

Information on medication for adults
Information on medication for children

AEDs do not stop seizures happening for everyone so other types of treatment may be considered, such as vagus nerve stimulation (VNS) or surgery.

Information on epilepsy surgery.
Information on VNS.

Reactions to a diagnosis

A diagnosis of epilepsy can affect people in different ways. Getting information about epilepsy and asking questions helps some people feel better about their diagnosis.

NSE runs an epilepsy helpline. It is a confidential line for anyone wanting to know more about epilepsy. This includes information on a wide range of topics and
emotional support. The helpline is available on: 01494 601 400 (Monday - Friday, 10am - 4pm).

Some people find counselling helpful. Your GP may be able to refer you to a counsellor. Or to find a qualified counsellor in your area, contact the British Association for Counselling and Psychotherapy (opens new window) or call 0870 443 5252.

Often people want to speak to someone else who has epilepsy to find out how they live with epilepsy. There are epilepsy support groups in the UK for people with epilepsy if you think this might help you.

UK Epilepsy Helpline: 01494 601400
Monday - Friday 10am - 4pm National call rate