Epilepsy Diagnosis and Classification

Getting a very complete medical history, including symptoms and length of seizures, is still one of the best ways for doctors to tell if a person has epilepsy and what kind of seizures he or she has. The doctor will ask questions about the seizures and any past illnesses or other symptoms a person may have had. Since people who have suffered a seizure often do not remember what happened, speaking with caregivers is also very important.

The physical exam and in particular the neurologic exam is an important component of evaluation for epilepsy and the underlying causes of epilepsy. Additionally, understanding a child’s functioning including development, learning, and behavior may aid a clinician in determining the cause of a child’s epilepsy and also understand how the epilepsy has impacted the child’s function.

Doctors use a number of different tests to find out if a person has epilepsy, and to learn what kind of seizures he or she experiences. Since there are other disorders that may seem like epilepsy, it’s important for the doctor to be certain that the diagnosis is correct.

Some of the tests used to diagnose epilepsy include:

EEG 

An EEG looks at the electrical activity of the brain called brain waves. To perform this test, doctors paste special sensors called electrodes to the scalp. The electrodes are attached to a recording device which records the minute electrical impulses passing through the brain below the electrode. This is the most common test for epilepsy because it can tell if there are abnormalities in the brain’s electrical activity. Epilepsy can be diagnoses if the patient experiences a seizure while attached to the EEG. However, since people who have epilepsy often have changes in their pattern of brain waves, even when they are not experiencing a seizure, these changes can also suggest the possibility of epilepsy even if no seizure is observed during the EEG.

While this type of test can help doctors tell if someone has epilepsy, it is not completely reliable. Some people continue to show normal brain wave patterns even after they have experienced a seizure. In other case, the unusual brain waves are generated deep in the brain where the EEG is unable to see them. Many people who do not have epilepsy also show some unusual brain activity on an EEG.

The possibilities of picking up abnormalities on the EEG include how close the EEG is done after a seizure event and the frequency of the seizure events. Doing an EEG with the patient awake and then asleep can also increase the likelihood of observing underlying abnormalities.

Sometimes, a patient may need an EEG to be done for a prolonged period to observe for abnormalities. Prolonged EEG recordings are sometimes done in a hospital setting along with video recording to determine if certain movements or activity changes are associated with EEG changes. Recently, ambulatory EEGs are used more to evaluate for seizures. For an ambulatory EEG, the electrodes are pasted to the scalp and then the patient goes home and does their usual activity while wearing the EEG. An ambulatory EEG can provide observations for a much longer period of time (e.g. days). 

Brain Scans

A brain scan cannot determine if a child has epilepsy. It can be used to try and determine if there is an underlying condition that would predispose a person to epilepsy or to help determine the cause of epilepsy. The brain scans used most often include CT (computed tomography), PET (positron emission tomography) and MRI (magnetic resonance imaging) scans. CT and MRI scans let doctors look at the structure of the brain, which can help them find brain tumors, cysts, structural changes, and other abnormalities. PET, functional MRI (fMRI) and SPECT (single photon emission computer tomography) scans can be used to check on the metabolic activity.

Less often used brain scanning techniques include magnetoencephalogram, (MEG) and magnetic resonance spectroscopy (MRS). MEG reads the magnetic signals produced by nerve cells to allow doctors to monitor brain activity. While MEG is similar to EEG, it does not need electrodes and it can find signals from deeper in the brain than an EEG. Magnetic resonance spectroscopy (MRS) can find abnormalities in the brain’s biochemical processes.

Medical History

Getting a very complete medical history, including symptoms and length of seizures, is still one of the best ways for doctors to tell if a person has epilepsy and what kind of seizures he or she has. The doctor will ask questions about the seizures and any past illnesses or other symptoms a person may have had. Since people who have suffered a seizure often do not remember what happened, speaking with caregivers is also very important.

Blood Tests

Doctors often take blood samples when evaluating a person who has seizures. A blood test cannot determine if a patient has epilepsy but specific blood tests might determine other disorders than epilepsy which have caused a seizure (e.g. such as seizures from low blood sugar) or might help determine the cause of a child’s epilepsy).

Developmental, Neurological, and Behavioral Tests

Doctors often use tests that measure the patient’s movement skills, behavior, and intelligence to learn how the epilepsy is affecting that person. These tests can give the doctor clues about what kind of epilepsy the person has.

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Resources:

Epilepsy Foundation
Diagnosing Epilepsy