Diagnosis of epilepsy

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Epilepsy is mainly diagnosed clinically, which means it is based on descriptions of the events provided by the patient and their relatives. It is very important, especially in the case of seizures with unconsciousness, that people who witnessed the event accompany the patient to their medical appointment, so they can give an accurate description of what happened. Patients who suffer recurrent seizures can use tools such as home video recorders to provide the neurologist with more objective data about what happens during their seizures.

Tests used to diagnose epilepsy

Diagnostic tests complement a good clinical history and can support the diagnosis. Some of these tests are: 

Patient with electrodes on the head to perform an encephalogram.

Electroencephalogram (EEG). It is next to the imaging, the most frequently used test to diagnose epilepsy. It involves placing some electrodes on the scalp and then registering the electric brain activity. There are different types of EEG (e.g., routine, sleep-deprived and all-night EEGs). This test is most useful when carried out in the first few hours after a seizure and while the patient is sleeping because epileptic discharges increase when asleep.

Brain with electrodes and encephalogram on a screen

Video–EEG monitoring. This involves recording video and EEG patterns simultaneously to try and capture a possible seizure. It can be conducted as an outpatient test (the patient goes to the hospital and is monitored for a few hours, or sometimes for a few days in a row) or in an inpatient setting (the patient is admitted for 5–15 days and their medication is progressively reduced to provoke and thus record a seizure). Simultaneous analysis of the video images and the brain’s electrical activity is used to refine the diagnosis and pinpoint the location of seizure onset.

Magnetic Resonance Imaging or MRI machine

Brain MRI (magnetic resonance imaging). This test is used to detect whether there are any brain injuries that could be causing the seizures. It should be carried out according to a specific epilepsy protocol and interpreted by an experienced radiologist.

Lying patient undergoing contrast injection for an encephalogram

Ictal single-photon emission tomography (SPECT). This test involves injecting a radioisotope during a seizure. The radioisotope binds to the discharging neurons and provides an image of the seizure onset and propagation area. It is performed on an inpatient basis during the video–EEG monitoring.

Positron emission tomography or PET scan of the brain

Positron emission tomography (PET). PET tests use very low doses of a radiotracer injected into a vein and help identify areas of the brain that consume low amounts of glucose, which is associated with areas of seizure onset.


Doctor with a questionnaire and cogwheels

Neuropsychological study. This test examines the cognitive functions (e.g., memory or language) that can deteriorate in certain types of epilepsy. It also helps predict any potential long-term consequences of epilepsy surgery.

Substantiated information by:

Antonio Jesús Donaire Pedraza
Francisco Gil López
Maria del Mar Carreño Martínez

Published: 22 May 2018
Updated: 22 May 2018

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