Tests for epilepsy
To diagnose epilepsy, your doctor will review your symptoms and medical history and may order a number of tests to help determine the cause of your seizures.
An important part of diagnosis is an eyewitness account – a good description of the seizure(s) or symptoms. If possible, take someone who has seen the seizure(s) or events when visiting the doctor, so they can also be asked questions.
Also try to find out if anyone in the family has ever had seizures before.
As part of diagnosis, the doctor will do routine physical and neurological examinations which may include blood tests. If epilepsy is suspected, there are several tests that may help to diagnose the condition and possibly establish a cause.
This is a brief guide to the tests that help diagnose epilepsy. Not everyone will need every test. If you are unsure why your doctor has suggested certain tests and not others, then it is best to ask.
Sometimes, all or many tests for epilepsy can return normal.
For more information about episodes that could be misdiagnosed or confused with seizures click here
Procedures to help diagnose epilepsy:
- EEG – This is a non-invasive test used to look at the electrical activity of the brain.
- Neuroimaging – These are brain scans and include MRI, SPECT, PET and CT scans.
- Neuropsychological tests – Look at how your brain is working and how the epilepsy affects your day to day functioning.
Tests for epilepsy
An electroencephalogram (EEG) is a test commonly done to look at the electrical activity of the brain – that is, the brain waves or how the brain is functioning. Brain cells communicate by producing tiny electrical impulses and seizures are a result of abnormal electrical activity, so it is logical to perform the EEG first.
If a person is thought to be having seizures, they are referred to a clinic to have an electroencephalogram (EEG). It is a simple, painless test and involves no needles or injections.
During the test, small discs called electrodes are placed on the surface of the scalp. The EEG machine then records the electrical activity of the brain on disc, computer or to paper.
An EEG usually takes about one hour. It is important to be relaxed because movement can affect results.
Most of the test is done with the eyes closed, and sometimes you will be asked to open them briefly. It is routine to be asked to breathe deeply (hyperventilate) for a 2-3 minutes and later have a flickering strobe light, flickering at various speeds. These forms of stimulus can provoke EEG changes in some forms of epilepsy.
For the test, it is important to have clean hair and scalp. Do not apply any hair products such as gel or hairspray on the morning of the test. It is also important to inform the person doing the test of any medications you are taking.
It is not uncommon for people with epilepsy to have a normal EEG in-between seizures.
An EEG recorded during sleep can also give additional information. This may sometimes be needed if your first EEG returns normal.
Also, no electrical current from the machine passes into the person’s brain during the procedure.
The technicians cannot read your thought processes or know what you are thinking.
Other types of EEG recordings
EEG video monitoring / telemetry
This is a method of recording the EEG over a long period, which using both EEG and video recording. This is done in hospital, either on a ward or in a specialised video-telemetry unit.
This procedure aims to record the person’s seizures (by video) and the brains electrical activity (EEG) at the same time. This combined information is one of the most valuable tools for diagnosing epilepsy. The advantage over routine EEG is the doctor is able to study exactly what happened during any attacks on the video and match this up with the EEG recording.
This monitoring may be needed for a few hours or several days, depending on the frequency of symptoms and seizures.
This monitoring is also used in the lead-up to surgery for epilepsy.
Video telemetry is, of course, quite restricting and you will most likely have to stay in hospital several days. Most institutions need a family member or friend to stay with you as a ‘buddy’. This is for safety reasons and the person is also needed to quickly alert staff to a seizure.
It is best to take something to do to keep you occupied. It can be a long, tiring and sometimes frustrating process.
Sleep deprived EEG / video telemetry
Some people may be asked to have a sleep-deprived EEG or video telemetry to record sleep which can increase the chance of detecting abnormal brain activity. If your routine EEG has been normal or has shown features which are not clear enough to make a definite diagnosis, the doctor may ask for a sleep EEG. Sometimes abnormalities associated with epilepsy can become more apparent in EEG during sleep.
The EEG changes a lot during sleep and sometimes these changes can trigger abnormal EEG changes seen with epilepsy.
For this procedure you will be asked to have less sleep the night before. This increases the chance of recording abnormal electrical activity. It is not a disaster if you do not sleep during the test, because even if you just become drowsy, there is still the chance of detecting abnormal activity.
The test can be performed in the same way as for a routine EEG or video telemetry, depending on the unit, but the person is asked to sleep during the test. Occasionally sleep is induced by a mild sedative, which is given about half an hour prior to recording, but most times you will be put in a quiet, relaxing environment with a bed and lights out.
EEG ambulatory monitoring
Sometimes abnormalities, events, or seizures are not picked up on the above tests. The hospital setting is far from normal, and often you are not under the everyday stressors that can trigger events. If the doctor would like something more wants to record a seizure or event, an ambulatory recording may be needed. This can be done when the person at home.
Ambulatory recordings are done when it is necessary to do a recording over several hours or days, making it more likely to detect any abnormalities or seizures. A compact portable EEG recorder may be worn which records brain activity while the person carries out usual daytime activities, and also during sleep. The person will also be asked to keep a diary of symptoms.
The electrodes are glued to the scalp and connected to the compact portable EEG recorder. This device is to be worn at home and there is usually a button you can press to mark an episode on the device.
This allows the EEG to be recorded over a much longer period than a routine EEG – for several days if need be – and in a normal setting. This greatly increases the chances of finding abnormalities. It is also more likely to actually record the EEG during an event, particularly and this may allow doctors to decide whether the events are seizures or not. The recording may also give a very clear picture of any patterns and how often they are occurring.
It is a very useful and cost effective tool to help in the diagnosis of epilepsy or other events.
For more information about ambulatory EEG click here
Neuroimaging – MRI, CT, SPECT and PET scans
When used for epilepsy, neuroimaging is images (pictures) taken of the brain, or a brain scan. It can be done to look at the structure and function of the brain. These scans may further help when diagnosing and treating epilepsy.
Pictures are taken of the brain that may show changes in brain tissue and how the brain is working. Changes may show for example:
- the presence of scar tissue from an injury
- a lesion or tumour
- degeneration or shrinking of brain tissue
- changes in blood flow in the brain
- changes to how some areas are functioning
Common imaging tests include:
MRI or Magnetic Resonance Imaging looks at the brain structure. It generates clear and detailed images of the brain without the use of x-rays, but instead uses strong magnetic fields and radio waves. Images can be generated in either two or three dimensions.
The MRI machine makes loud thumping and banging noises. Earplugs or earmuffs should be available.
Because of the strong magnetic field people with pacemakers, cerebral aneurysm clips and any other metal surgical implants will not be able to have a MRI scan.
It is important to remove jewellery, hairclips, hearing aids, credit cards, coins, keys, even makeup and hair gels which could interfere with the scan.
The MRI scan is not known to have any harmful effects.
It is best to tell staff or your GP when booking the scan if you suffer from claustrophobia (fear of being in a confined space) and you may be allowed to take a light relaxant before the scan.
For more information on MRI scans Click Here
Functional MRI (fMRI).
A functional MRI measures the changes in blood flow that happens when specific parts of the brain are working. Doctors may use an fMRI before surgery to identify the exact locations of critical functions, such as speech and movement, so that surgeons can avoid injuring those places while operating. Click here to see more.
SPECT uses a computer to generate pictures of the blood flow within the brain. It is often done twice, once when no seizure has occurred (interictal) and another immediately after a seizure (ictal) – although the radioactive substance is injected and absorbed while the seizure is happening. Blood flow in the area causing seizures should be lower in-between seizures and increased during seizures.
This test is often used as part of the workup for surgery for epilepsy.
For more information on SPECT click here
PET scanning measures metabolic activity showing how the brain is working (function) rather than how it looks (structure). It produces a 3D image of the brain. In a person with epilepsy, the area causing seizures will have less activity because the cells are not as active in-between seizures (unless a seizure occurs when the substance is injected which will increase brain activity in this region).
The person will be asked to fast for the test because it is glucose metabolism that is being measured. With someone with epilepsy, often a video telemetry EEG is performed at the same time, so it is necessary to arrive early to set this up.
PET may be done to help establish if someone is suitable for epilepsy surgery.
For more information on PET scans Click Here
Computed Tomography (CT) is a procedure that uses x-rays to take pictures of the brain. It is not commonly performed when trying to diagnose epilepsy. CT scans can show abnormalities in the brain that might be causing seizures, such as tumours, bleeding, and cysts.
For more information on CT scans Click Here
Although these tests don’t diagnose epilepsy, they assess a range of learning domains including thinking, memory and speech skills. This gives your doctor an overall picture of how well your brain works and if there are any areas that aren’t working well, which may be the area causing the seizures. It can also help find out how the epilepsy is affecting your ability to reason, concentrate, solve problems, or remember.
Most of the tests done include answering questions or performing tasks. You may do some on a computer, using pencil and paper, or using other objects. The tests are meant to test your limits, so don’t be disheartened if they seem hard.
For more information about neuropsychological tests click here
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