DIAGNOSIS: DIAGNOSTIC TESTS FOR EPILEPSY

The actual diagnosis of epilepsy can be made by the doctor after the patient has explained what happens during and after a seizure. This the patient can do easily with the help of a witness as some people lose consciousness and they are totally unaware of what is happening. The doctor may also suggest some tests for an actual diagnosis of epilepsy.

There are a number of procedures available to assist the doctor in making an accurate diagnosis of the type of epilepsy a person has. The doctor may recommend the following tests;

1. Electroencephalogram (EEG)

An electroencephalogram (EEG) is a written record of the brain’s electrical rhythm. The EEG will pick tiny electrical signals given off by the communicating nerve cells. This will show that neurons in the brain are communicating in a normal manner or some are firing in an unusual manner. Also it will reveal the part of the brain that is affected.

To record these rhythms a small number of small metal discs, called electrodes, are placed against the scalp at various points. They are held in place by a glue-like substance, which can easily be washed off later. With the electrodes in place, the person will either sit or lie down in a restful state with his or her eyes closed. The test takes about thirty minutes. During this time the person will be asked to perform certain simple tasks, such as blinking, breathing deeply or some form of mental activity. The test usually includes a series of flashing lights at various frequencies since some forms of epilepsy may be stimulated in this way.

Sometimes it is necessary to obtain a recording over a period of hours or days. A portable EEG can be attached to the person to perform the test while carrying out normal activities, including sleep. This is called EEG telemetry. In certain circumstances it is necessary to admit the person to hospital and monitor the brain’s activity through EEG telemetry and continual video recording at the same time. This enables the doctor to match brain rhythms with behaviour and seizure activity.

2. The Computerized Tomography (CT Scan)

Computerized Tomography (CT) provides cross sectional images of the brain. It is used to reveal any obvious structural abnormality or damage which might be present. The person lies on an X-ray table, which is moved slowly into the CT unit, which contains the scanner. Only the upper part of the head moves within the scanner. An X-ray device rotates around the person’s head in an arc formation, recording a number of images of the brain. To make the images clearer, a dye is injected into a vein in the person’s arm. The whole procedure takes about 45 minutes and provides valuable information for diagnosing epilepsy.

3. The Magnetic Resonance Imaging (MRI)

Magnetic Resonance Imaging (MRI) is a method of scanning the brain without using x-rays. It uses magnetic fields and radio waves to form an image of the structure of the brain. The MRI reveals far smaller structural abnormalities that the CT scan can not reveal and the MRI easily points out if a person is suitable for brain surgery. During the MRI scan the person’s head is surrounded by a magnetic field. The energy changes that result are used to produce computer images, which look like two-dimensional slices through the brain.

The magnetic field and the radio frequency waves are completely painless and cause no physical harm. At most the person may feel some discomfort from having to lie still in the “tunnel” while the machine is scanning their head. To minimize discomfort, a fan circulates air and a mirror at the end of the tunnel allows the person to see the room and scanner operator. An intercom call button is right beside the person’s hand so verbal communication can be maintained throughout. Some people choose to wear earplugs to block out the metallic thumping noise of the machine. The MRI scan takes about an half and a hour.

4. Positron Emission Tomography (PET)

Positron Emission Tomography (PET) is a non-invasive imaging technique that creates a three-dimensional image of the brain. Short acting radioisotopes are injected into the blood. The person rests for about 30 minutes. During the scan a mask is placed gently over the person’s face to limit movement. The functioning of the brain is revealed such as the way in which blood flows. This type of brain scan is extremely costly and has been largely replaced by the Single Photon Emission Computed Tomography, (SPECT Scan) which uses different radioisotopes, which are able to hold the image of the blood flowing through the brain for up to 24 hours. The SPECT Scan looks at blood flow through the brain during a seizure (ictal phase) and compares this with inter-ictal (seizure free) scan this highlights the “hot spot” or origin of the seizure in the brain. The actual scan usually takes about 20 to 30 minutes.

For more information please contact the Swaziland Epilepsy Organization at 404 7028 or 7712 9856. Email - admin@epilepsy.org.sz
Website – www.epilepsy.org.sz