The most frequently used diagnostic tool for epilepsy is the electroencephalograph (EEG). This test uses electrodes attached to the scalp to read the brain's electrical messaging system. People who have epilepsy often have unusual brain wave patterns even when they are not having a seizure. EEG is most accurate, however, when it is performed within 24 hours of a seizure.
The EEG test usually lasts about an hour and can be done in the doctor's office or as an outpatient at the hospital. In some cases, however, a doctor may want a 24-hour recording. Brain activity can be quite different during sleep, and it can be helpful to measure brain waves during sleep time.
Portable EEG units can be used to monitor brain waves throughout the day and during many different types of activities. The doctor may also want to do video monitoring along with the EEG. Some medical centers have special video monitoring units that help them determine whether seizures are caused by epilepsy or by some other condition such as narcolepsy or heart disease.
About half the people who have had an epileptic seizure have normal EEG readings. Therefore, other diagnostic tests may be needed.
Brain imaging is often used when an adult has had a first seizure or when a child is having convulsive seizures that are not caused by fever.
Computerized tomography (CT or CAT scan) and Magnetic Resonance Imaging (MRI) can be used to reveal the structure of the brain. Both use computers to produce precise images of the brain. These tests are useful in identifying tumors, cysts, and other structural abnormalities.
Positron Emission Tomography (PET) and functional MRI (fMRI) can be used to monitor the brain's activity and to detect abnormalities in its working. These tests can find damaged areas in the brain that are the focal points for seizures. They can help determine whether a patient is a good candidate for surgery and can be used to guide surgery.
Doctors use blood tests to screen for metabolic or genetic disorders that may be linked to seizures and to look for other conditions that may cause seizures, such as infections, lead poisoning, anemia, or diabetes. Metabolic and genetic screening is most often done when examining a child.
Developmental, Neurological, And Behavioral Tests
Tests to measure coordination and muscle control, behavior, and intellectual capacity can help find out what is causing epilepsy and how the seizures may be affecting the patient.