How is epilepsy diagnosed?

The evaluation of patients with epilepsy is aimed at learning the type of seizures (epileptic or non-epileptic) and their cause, since various seizure types respond best to certain treatments. The diagnosis is based on:

  • The patient's medical history, including any family history of seizures, associated medical conditions, and current medicines the patient is taking. Your doctor will ask you some important questions, including the following:
    • At what age did the seizures begin?
    • What circumstances surrounded your first seizure?
    • What factors seem to bring on the seizures?
    • What do you feel before, during, and after the seizures?
    • How long do the seizures last?
    • Have you been treated for epilepsy before?
    • What medicines were prescribed and in what dosages?
    • Was the treatment effective?
  • Others who have often seen you before, during, and after seizures, such as family and close friends, should be with you at the appointment to give details of your seizures if they involve loss of consciousness (if you passed out).
  • A complete physical and neurological exam of muscle strength, reflexes, eyesight, hearing, and ability to detect various sensations is used so that your doctors can better understand the cause of your seizures. Additional testing often includes:
    • An electroencephalogram (EEG), which measures electrical activity in the brain
    • Imaging studies of the brain, such as magnetic resonance imaging (MRI)
    • Blood tests to measure red and white blood cell counts, blood sugar, blood electrolyte levels, and to check how well your liver and kidney are functioning. Blood tests also help rule out other illnesses.
    • Other tests are used as needed, including magnetic resonance spectroscopy (MRS), positron emission tomography (PET), and single photon emission computed tomography (SPECT).

The most important part of the evaluation is the electroencephalogram (EEG) because it is the only test that directly detects electrical activity in the brain (seizures are defined by abnormal electrical activity in the brain). During an EEG, electrodes (small metal disks) are attached by glue to specific locations on your head. The electrodes are also attached to a monitor to record the brain's electrical activity. The EEG is useful to confirm a diagnosis of epilepsy and to determine the type of epilepsy.

The routine EEG procedure takes about 90 minutes and allows for about 20 minutes of brain wave recording. The results of a short recording may be normal even in people who are known to have epilepsy. Therefore, a repeat EEG recording of 180 minutes or more might be necessary.

Prolonged EEG-video monitoring is an even better diagnostic method. During this type of monitoring, an EEG monitors (checks) the brain's activity and cameras videotape body movements and behavior during a seizure. In order to perform prolonged monitoring, the patient may have to spend several days in a special hospital facility. Prolonged EEG-video monitoring is sometimes required to definitively diagnose epilepsy and to choose the best treatment option.

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