Diagnosis
In some cases, all or many tests for epilepsy can return normal.
An important part of diagnosis is an eyewitness account - a good description of the event(s) or symptoms. If possible, take an eyewitness 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.
The following pages offer a guide to the tests used when diagnosing epilepsy. Not everyone with epilepsy needs every test. For example, CT and MRI are rarely useful in people with genetic forms of epilepsy, while PET and SPECT are generally used in people undergoing assessment for surgical treatment.
If you are unsure why your doctor has ordered or not ordered a particular test, you should ask.
For more information about episodes that could be misdiagnosed or confused with seizures click here
Procedures for aiding the diagnosis of 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 CT, MRI, SPECT and PET scans.
EEG (Electroencephalogram)
Routine EEG
An Electroencephalogram (EEG) is a test commonly performed 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. 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.
A normal EEG recording (Picture Courtesy of Wikipedia)
During the test, small discs called electrodes are placed on the surface of the scalp by parting the hair and holding them in place with temporary glue, or sometimes a special cap. 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 performed 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.
Many people who have epilepsy have normal EEGs in-between seizures.
An EEG recorded during sleep can also give added information. This may sometimes be required 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 more sophisticated method of recording the EEG over long periods, which uses both EEG and video recording. This is done in hospital, either on one of the wards or in a specialised video-telemetry unit.
This procedure aims to simultaneously record persons episodes (by video) and the brains electrical activity (EEG). This combined information is valuable in diagnosis and understanding a person's events and their correlation with EEG. 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 simultaneous EEG recording.
This monitoring may be needed for hours or days, depending on the frequency of symptoms and episodes.
Monitoring is usually done in hospital and is a good way for the doctor to determine an accurate diagnosis. It is also used in the lead-up to surgical treatment of epilepsy.
The disc electrodes are glued to the scalp and wrapped in a bandage. There is a head-box which is sometimes wrapped on top of the head, or placed around the neck or directly beside you. There is a lead from this head-box it to monitoring equipment, confining the you to the hospital room. The camera is focussed on you and can be moved to different positions in the room. There is a also ‘seizure alarm’ button to press if an event occurs.
Video-telemetry is, of course, quite restricting. It is important to remain in view of the camera for most of the time, and you are often given a remote control to move the camera when or after you move. This means being in or on the bed or in a chair at the bedside. Of course, the camera cannot record in the bathroom or toilet. However, if you are in hospital for several days, you will not be connected to the system for every second. The cable connecting the head-box to the videotelemetry system can be unplugged quite easily, allowing for showers etc.
Most institutions require a family member or friend to stay with you as a 'buddy'. This person is also needed to quickly alert staff to a seizure.
It is preferable that some hobbies or activities are taken into hospital to keep you occupied. It can be a long and sometimes frustrating process. Many institutions also encourage you to wear everyday clothes rather than pyjamas (it is easier with clothes that button or zip up the front rather than pull over the head).
Sleep deprived EEG / video telemetry
Some people may be asked to have a sleep-deprived EEG or video telemetry to record sleep and increase the chance of detecting abnormal brain activity. If your routine EEG has been normal or has shown features which are suspicious but not clear enough to make a definite diagnosis, the doctor may ask for a sleep EEG. This is because abnormalities can become more apparent in EEG during drowsiness and light sleep - particularly some abnormal brain activity seen in epilepsy.
The EEG changes significantly during sleep and sometimes these changes can trigger abnormal EEG changes seen with epilepsy.
For this procedure you will be asked to reduce your sleep time the night before. This increases the likelihood of recording abnormal electrical activity. It is not a disaster if you do not sleep as there is still the likelihood of detecting abnormal activity, especially if you are drowsy.
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, episodes, 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 definitive to diagnose your condition, an ambulatory recording may be asked for.
In certain cases it is necessary to obtain a recording over several hours or days making it more likely to detect any abnormalities or episodes. The electrodes are glued to the scalp and connected to the a compact portable EEG recorder. This is worn to record brain activity while you carry out normal daytime activities, and during sleep. This device can be taken home and you will also be asked to keep a diary of symptoms.
There is often 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 detecting abnormalities.
It is also more likely to actually record the EEG during an attack, particularly if these are occurring quite often. This may allow doctors to distinguish whether the episodes are epilepsy or not. The recording may also give a very clear picture of any patterns or how often they are occurring.
Neuroimaging - MRI, CT, SPECT and PET scans
Neuroimaging, or brain scanning, is predominantly performed to look at the structure of the brain. The techniques outlined below may further assist in the diagnosis of epilepsy. Pictures are taken of the brain that may show changes in brain tissue structure and cell function. Changes may indicate 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 metabolism of substances such as glucose
Common tests include:
MRI Scanning
MRI or Magnetic Resonance Imaging produces clear and detailed images of the brain without the use of x-rays. It uses strong magnetic field and radio frequency waves that produce and measure energy changes in the brain and then generates images. Technology has advanced and the MRI can now produce three-dimensional images of the brain on a computer. Two-dimensional images can be printed onto film.
The person is lies on a table and the table moves inside the scanner, which is like a tunnel. During the scan, the machine makes a loud thumping noise. This can be distressing for those who dislike confined spaces, a mirror at the person's head provides a view of the room and the operator, while a call button and an intercom allows contact. Earplugs should also be available.
The procedure lasts from 30-45 minutes.
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 advisable to tell staff prior to the scan if you suffer from claustrophobia (fear of being in a confined space).
Again, complete stillness is required during this test and young children may require sedation or a light, general anaesthetic. The entire procedure takes from 30-60 minutes.
For more information on MRI scans Click Here.
CT Scanning
Computed Tomography (CT) is a procedure that uses x-rays to take pictures of the brain, displayed as cross-sectional images or slices.
The person lies on a table, and only the head moves into the CT scanner. Pictures are taken at many angles to generate the brain images. Sometimes to enhance the different structures and give more contrast, a dye is injected into a vein of the arm or hand. On occasion a person is allergic to the dye: this may cause a skin rash and, rarely, difficulty with breathing.
The entire procedure takes from 30-45 minutes. The test is painless except for the discomfort of the injection if this is required.
As complete stillness is required during the test, young children may require sedation or a light, general anaesthetic.
For more information on CT scans Click Here.
SPECT Scanning
SPECT also uses a computer to generate pictures of the blood flow within the brain. It is often performed twice, in a seizure free period (interictal) and immediately after a seizure (ictally) – although the radioactive substance (Cerotec) is injected during the seizure. Both scans are compared to identify changes in blood flow in the brain. Blood flow in the area triggering seizures can be reduced in-between seizures and temporarily increased during seizures.
A radioactive substance is injected into a vein and is carried to the brain via the bloodstream. The person lays on a table and the head moves inside the scanner. The scan produces a picture of the brain highlighting blood flow.
Scans usually take 30 minutes and are mostly performed in hospital as part of EEG/Video monitoring. This test is often used as part of the workup for surgery for epilepsy.
PET Scanning
PET scanning measures metabolic activity, looking at function rather than structure of the brain. It produces a three dimensional image of the brain. In a person with epilepsy, the region of the brain where the seizures originate from often has decreased metabolism, the cells are not as active in-between seizures (unless a seizure occurs during the uptake of the substance which will increase activity in the region, thus increases metabolism).
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 simultaneously, so it is necessary to arrive early for application of the EEG electrodes.
The radioactive substance is injected and the person will be given ear plugs and eye patches to reduce any outside stimulation that can influence the scan. This is a 30-minute period and remaining awake at this time is also important. Blood tests will also be taken during this period. After this, the scan commences, a mask will be put over your face to assure no movement, and your head moves into the scanner.
It can last from 30-45 minutes.
PET is may be done to help establish if someone is suitable for epilepsy surgery.
For more information on PET and SPECT scanning Click Here.
