Causes and Diagnoses

Causes and Diagnoses of Epilepsy and Seizure Disorders

Epilepsy is a condition that can have many causes and can occur at any age. In generalized epilepsy, abnormal electrical discharges involve all areas of the brain, which may look completely normal and have no structural abnormality. This type of epilepsy is thought to be caused by a genetic predisposition. In some cases, generalized epilepsies are associated with universal brain abnormalities that are sometimes caused by:

  • Brain infections
  • Head injuries
  • Lack of oxygen

Diagnosing Epilepsy and Seizure Disorders

Many people with seizures are first seen in an emergency room. About half of the people who experience a single seizure will never have another seizure and treatment is not recommended. Those with recurrent seizures are first treated as an outpatient by a neurologist or general medicine physician. The first step in diagnosing epilepsy involves reviewing your seizure history. Your physician will request:

  • Standardized seizure questionnaire
  • Seizure diary
  • Medication log
  • Information from someone who has observed the seizure

Your physician will also perform a thorough physical examination of your nervous system, checking mental function such as memory, simple arithmetic, naming objects, movement, muscle strength, walking, balance and coordination, sensation and reflexes.

Diagnostics and Testing

Tests and Procedures

In order to reach a diagnosis, one or more of the following tests may be ordered to help your physician provide you with the best treatment options. For more information, click the name of the test to take you to the health encyclopedia.

Electroencephalograph (EEG)

Electroencephalograph (EEG) records the electrical activity in the brain. Electrodes are pasted to the patient's head in specific places, and wires are then connected from the electrodes to an EEG machine. Brain wave activity may show a pattern, which helps the doctor determine whether or not someone has epilepsy. Sharp waves support the diagnosis of epilepsy and can help identify the type of epilepsy.

Diagnostic Video EEG Monitoring

Diagnostic Video EEG Monitoring is used to diagnose patients who do not respond to epilepsy medications. Video EEG monitoring is continuous EEG monitoring and continuous videotaping of the patient.

This monitoring is usually performed in the hospital over several days. This allows the doctor to observe the behavior that occurs during the seizure and how it is related to the electrical activity in the brain. Often the patient's anti-epileptic medication is reduced to allow seizures to occur so they can be recorded.

Video EEG monitoring can help to:

  • Confirm the diagnosis of epilepsy
  • Determine the type of epilepsy and the best medication for it
  • Allow medication change under supervision
  • Pinpoint the region of the brain where the seizures begin, which is essential if epilepsy surgery is being considered
  • Learn what to expect during Video-EEG Monitoring (pdf)

Brain Imaging

Magnetic Resonance Imaging (MRI) or Computerized Tomography (CT)

Magnetic Resonance Imaging (MRI) or Computerized Tomography (CT) scan may be performed to look for any growths, scarring, or other conditions in the brain that may be causing seizures.

PET Scan (Positron Emission Tomography)

PET scan (Positron Emission Tomography) shows the brain's use of oxygen or sugar (glucose). A very low, safe dose of a radioactive substance is injected into a vein in the arm, and the scanner records its circulation. The image shows areas of the brain that are more active than others. This test can help identify the area(s) of the brain where partial seizures begin.

Ictal SPECT (Single Photon Emission Computed Tomography)

Ictal SPECT (Single Photon Emission Computed Tomography) is a scan that shows the blood flow in the brain and is used to locate the site where the seizure begins. A very low, safe dose of a radioactive substance is injected into a vein in the arm as soon as possible after a seizure begins. The scan is performed soon afterwards. An image is produced which highlights the area of greatest blood flow during the seizure.

Functional MRI (fMRI)

Functional MRI (fMRI) is a brain scan that evaluates the structure of the brain that is responsible for movement or sensation activity. The person will be asked to look at pictures, listen to sounds, or squeeze a ball during the scan, and the image will highlight the area of the brain engaged in the task.

Magneto-encephalography (MEG)

Magneto-encephalography (MEG) measures electrical currents in the brain. MEG is similar to an EEG but is much more accurate. When it is combined with MRI, it is extremely helpful for identifying areas of the brain where the seizure begins.

Neuropsychological Testing

Neuropsychological testing measures a person's memory and cognition. Neuropsychological testing can sometimes help identify areas of the brain that are not functioning normally, which may provide a clue to the area where the seizure begins. For example, impaired memory for words may indicate abnormal left temporal function.

Wada Test

Wada test is performed during and brain angiogram to determine which side of the brain is responsible for language and memory. A medicine will be injected to put one side of the brain to sleep at a time. The patient is asked to read and talk during the exam.

Learn what to expect during Wada Testing (pdf).

Diagnostic Tests

Some people may require an advanced diagnostic workup if the cause of the seizure is unclear, the seizures continue despite adequate medication, or the side effects of the medication are intolerable. In those cases, your physician may order one or more of the following diagnostic tests:

Related Resources


  • Video-EEG Monitoring: EEG portion of the test looks at electrical activity of the brain and the video recording shows how the body responds during a seizure.
  • Wada Testing: Learn more about this test, which examines each side of your brain.
  • Specialized Treatment for Epilepsy: The Northwestern Medicine Comprehensive Epilepsy Center maintains the highest designation by the National Association of Epilepsy Centers.


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