Epilepsy can be diagnosed when an individual has had two seizures without a clear provoking cause or one seizure with a high risk of having more seizures. A physician taking care of an individual who had an event concerning for a seizure will use information from the individual’s medical history as well as the results of diagnostic tests to determine what type of seizures and what type of epilepsy that individual has. Early identification of the type of seizures and the type of epilepsy is important as it often influences treatment decisions and long-term prognosis.

Potential Types of Diagnostic Tests

  • Medical History
    • Obtain a clear history of the event concerning for a seizure, including from a witness who can describe what the event looked like. Information such as whether one part of a person’s body moved first or how the person appeared during or after the event can help determine what type of seizure they may have had.
      • Identify key components of past and recent medical history including:
        • Known risk factors for seizures and epilepsy:
          • Complications around the time of birth, such as being born early (prematurely)
          • Traumatic brain injury
          • Central nervous system infections
          • Febrile seizures
          • Other medical conditions
        • Recent symptoms (illness, head injury, lack of sleep, dehydration)
        • Developmental history
        • Medications/exposure to toxins (ethanol alcohol, illicit drugs, etc.)
        • Family history
        • Febrile seizures or epilepsy in 1st and 2nd degree relatives
  • Laboratory tests
    • Common tests:
      • Glucose
      • Electrolytes
      • Serum alcohol level
      • Toxicology drug screen
      • Anti-seizure medication levels (where applicable)
    • Blood tests usually don’t explain why a person had a seizure and are not needed in all cases unless there are other concerning signs or symptoms.
  • Electroencephalogram (EEG)
    • An electroencephalogram (EEG) is a test that measures the electrical activity in the brain. It can help determine what type of seizures or epilepsy a person has and if seizures are coming from one area of the brain.
    • This test may be performed immediately after a person has a seizure (for example in the emergency room) or when the person sees a neurologist as an outpatient.
  • Neuroimaging
    • Neuroimaging refers to tests that take pictures of the brain to identify any changes in the brain’s structure that could explain why a person may have had a seizure.
    • Computed Tomography (CT) scans are rapid tests that detect serious abnormalities, such as bleeding in the brain or large tumors, that may require immediate treatment and are often performed in the emergency room.
    • Magnetic Resonance Imaging (MRI) scans take more detailed pictures and can identify more subtle changes in structure of the brain. These scans usually happen a few days or weeks after a person has had a seizure. Because they take a long time to obtain, children and adolescents often require sedation with medication to help them lie still during MRI scans.
  • Other Tests
    • Genetic tests look for changes in how a person’s body was programmed to develop that could make them more likely to have epilepsy. These include but are not limited to:
      • Karyotype (less commonly used in current practice)
      • Chromosome Microsomal Analysis
      • Targeted gene testing/gene panels
      • Whole exome sequencing
    • Metabolic tests look for changes in the how the body processes nutrients that could put them at risk for seizures. These include but are not limited to:
      • Blood tests or urine tests
      • CSF: Sometimes a physician will recommend a lumbar puncture to collect the fluid around the brain and spinal cord, called cerebrospinal fluid (CSF) for specialized testing.
    • Other testing
      • A referral to see an eye doctor, ophthalmologist
      • Rarely skin or muscle biopsies

Additional Resources

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American Academy of Pediatrics