Diagnosing epilepsy

• Did anything trigger (set off) the seizure, for example, did you feel tired, hungry, or unwell?
• Did you have any warning that the seizure was going to happen?
• Did your mood change, for example, were you excited, anxious, or quiet?
• Did you make any sound, such as crying out or mumbling?
• Did you notice any unusual sensations, such as an odd smell or taste, or a rising feeling in your stomach? 
• Where were you, and what were you doing before the seizure?

• Did you appear to be ‘blank’ or stare into space?
• Did you lose consciousness or did you become confused?
• Did you do anything unusual, such as mumbling, wandering about, or fiddling with your clothing?
• Did your colour change (become pale or flushed) and if so, where (face or lips)?
• Did your breathing change (for example, become noisy or look difficult)?
• Did a part of your body move, jerk, or twitch? Did you fall down, or go stiff, or floppy?
• Did you wet yourself?
• Did you bite your tongue or cheek?

• How did you feel after the seizure – did you feel tired, worn out, or need to sleep?
• How long was it before you were able to carry on as normal?
• What else did you, or another person, notice ?

It may be helpful to record some information about your seizures to show the specialist when you see them. 

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

Sometimes the cause of someone’s epilepsy can be found, for example, following a head injury, a brain infection (such as meningitis), or a stroke. Some inherited conditions (passed from parent to child), such as tuberous sclerosis, can cause epilepsy. 
However, for many people there are no clear reasons why they have epilepsy.

A sample of blood will usually be taken from your arm, with a syringe. The sample is used to check your general health and to rule out other possible causes for your seizures, such as low blood sugar levels or diabetes.

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. 

An ECG does not give out electrical signals, so having one doesn’t hurt. An ECG can help to rule out if the cause of seizures is due to the way the heart is working.

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

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

Before the test, the technician measures your head to work out where to place the electrodes. Each electrode is held in place using a sticky paste. Once the electrodes are attached they are connected to the recording machine. The test lasts about 30 minutes and you will probably be sitting or lying down. 

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, known as epileptiform brain activity, can sometimes be seen on an EEG recording. Some people can have epileptiform brain activity even when they do not appear to be having a seizure, so an EEG can be particularly useful for them.

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

Some people with epilepsy have seizures that are started, or ‘triggered’, by flashing lights. This is called photosensitive epilepsy and affects about 3% of people with epilepsy. An EEG will usually include testing for photosensitive epilepsy. This involves looking at a light which will flash at different speeds. If you are worried about this you can talk to the technician. 

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

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

For most people there is more chance of irregular brain activity showing when they are tired or when they are going to sleep. 

Having a sleep-deprived EEG might help to get a more useful reading. This test is done in the same way as a normal EEG (see above) but you sleep during the test. To help you sleep you may be asked to stay awake for some, or all, of the night before. In some cases you may be given a mild sedative to help you to sleep.

An ambulatory EEG works in the same way as a normal EEG but it 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. Because brain activity is recorded for longer, there is more chance of a seizure being recorded than during the normal 30 minute test.

Video telemetry usually happens in hospital, normally over a few days. During your stay you will have your own room. A video camera, often mounted on the wall, will record what you are doing. At the same time you will wear a portable EEG so that you are able to move around your room. 

Sometimes you may be able to have video telemetry at home with portable monitoring and video equipment but this is not available in all EEG departments. Being videoed while wearing an EEG means that, if you have a seizure, your doctors can compare the electrical activity of your brain with what is happening to your body. 

In some situations you may also be offered genetic testing.

If the neurologist thinks that autoimmune encephalitis may have been the cause of your seizure, you may be referred for antibody testing.

An MRI scan looks at the structure of the brain and may help to find the cause of your epilepsy. During the scan, detailed pictures are produced using strong magnetic fields. 

Because of the magnetic fields, metal objects in or near the machine can affect, or be affected by, the machine. Before having an MRI scan you will need to remove any metal objects such as jewellery, hearing aids, coins, or keys. If you have a heart pacemaker or any surgical implant that contains metal you may not be able to have an MRI scan.

The scanner makes a loud knocking noise, so before it starts you will be given earplugs to wear. You will also be given a buzzer to hold so you can let the technician know if you are uncomfortable or feeling unwell during the scan. 

The technician is usually on the other side of a window in another room during the scan, but an intercom means you can talk to them. There is also a mirror inside the scanner so you can see the technician during the scan. 

You may be able to have someone in the room with you during the scan. Having an MRI scan to help diagnose epilepsy usually takes about 30 minutes. During the scan you will lie on a platform which slides inside the scanner (a bit like going into a tunnel).

Lying still during the scan is important so that the machine can take clear pictures of your brain. An MRI scan is usually a series of short scans with breaks in between, rather than one long scan. Between each scan the technician might use the intercom to check that you are ok.

Some people may have a CT scan if they are not able to have an MRI scan (for example, if they have a heart pacemaker, if they might need to have an anaesthetic to have an MRI, or if information about what might be causing their seizures is needed quickly). 

CT scans use X-rays to take images of the brain. CT scans are not suitable if you are pregnant because the X-rays could affect an unborn baby.

Images from a CT scan are less detailed than those from MRI scans. 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.