Medically reviewed by Carina Fung, PharmD, BCPPS

Epilepsy Diagnosis

Generally speaking, epilepsy is diagnosed13 when a person has had two unprovoked seizures (or one unprovoked seizure with a high chance of having more) that weren’t caused by a known, reversible medical condition, such as alcohol withdrawal or extremely low blood sugar (hypoglycemia).

In order to diagnose you with epilepsy, your healthcare provider will ask about your signs, symptoms, and personal and family health histories. They may also order several tests to diagnose the condition and determine the underlying cause of your seizures. This evaluation may include14:

  • Blood tests: Blood tests may be used to check for signs of conditions that may be associated with seizures, including infections and genetic conditions.
  • Neurological exam: Your provider or a specialist may check your motor abilities, behavior, mental function, and other faculties in order to diagnose your condition and determine the type of epilepsy you may have.

Your healthcare provider may also suggest that you undergo testing used to detect brain abnormalities, including:

  • Electroencephalogram (EEG): EEG is the most commonly used test to diagnose epilepsy. This test uses electrodes attached to your scalp with a cap or adhesive substance to record your brain’s electrical activity. People with epilepsy commonly have changes in their normal brain wave patterns, even when they aren’t having a seizure.

    The provider conducting this test may monitor you on video while you’re awake or asleep in order to monitor any seizures you may experience. Recording your seizures may help them determine the kind of seizures you have and rule out the possibility of other conditions.

You may be instructed to do something that will trigger seizures, such as getting little sleep, prior to this test. An EEG may be performed in a provider’s office or in the hospital. In some cases, you may also have an ambulatory EEG. This involves wearing the monitoring device home while it records your seizure activity over the course of several days.

  • High-density EEG: A high-density EEG involves placing electrodes closer together (roughly half a centimeter apart) than in a conventional EEG. This test may help a provider more precisely determine which parts of your brain are affected by your seizures.

  • Computerized tomography (CT) scan: CT scans use X-rays to take cross-sectional images of your brain, helping to reveal abnormalities (such as tumors, cysts, or bleeding) that may be causing seizures.

  • Magnetic resonance imaging (MRI): MRI uses radio waves and powerful magnets to create a highly detailed image of your brain. Like CT scans, MRI can help detect abnormalities in the brain.

  • Functional MRI (fMRI): This type of MRI measures how your blood flow changes when specific areas of your brain are engaged. An fMRI may be used before surgery to identify the precise locations of the areas of your brain responsible for critical functions (such as speech and movement), so surgeons can avoid damaging them while operating.

  • Single-photon emission computerized tomography (SPECT): This type of test involves injecting a small amount of low-dose radioactive material into a vein to create a detailed, 3-D map of the blood flow activity in your brain during seizures.

    A SPECT test is primarily used if you’ve undergone an EEG and MRI, and neither test was able to determine the location in your brain where your seizures are originating. In some cases, a provider may conduct a particular type of SPECT test called subtraction ictal SPECT coregistered to MRI (SISCOM) to collect even more highly detailed results.

  • Positron emission tomography (PET) scan: Like SPECT tests, PET scans involve injecting low-dose radioactive material into a vein to help visualize the active areas of the brain and detect any abnormalities that may be causing seizures.

  • Neuropsychological testing: Neuropsychological testing uses a series of tests to assess your cognitive (thinking), memory, and speech skills. The results of these tests can help your provider determine which areas of your brain are affected by your epilepsy.

Along with the results of these tests, your provider may use a combination of the following analysis techniques to determine where in your brain your seizures start:

  • Magnetoencephalography (MEG): This test measures the magnetic fields produced by your brain activity to identify the areas in which your seizures may be originating.
  • Curry analysis: This technique involves projecting EEG data onto an MRI of the brain to reveal where your seizures are occurring.
  • Statistical parametric mapping (SPM): SPM is a method that involves comparing the areas of the brain that have increased metabolic activity during seizures to normal brains, which can also help indicate where your seizures begin.

Ultimately, an accurate diagnosis of the types of seizures you have and where they originate provides the best chance for finding the most effective treatment for your epilepsy.

Disclaimer: The information on this site is generalized and is not medical advice. It is intended to supplement, not substitute for, the expertise and judgment of your healthcare professional. Always seek the advice of your healthcare professional with any questions you may have regarding a medical condition. Never disregard seeking advice or delay in seeking treatment because of something you have read on our site. RxSaver makes no warranty as to the accuracy, reliability or completeness of this information.

If you are in crisis or you think you may have a medical emergency, call your doctor or 911 immediately.