The electroencephalogram (or EEG) is a test that measures the electrical activity of the brain. In reality, the examination is called electroencephalography, and electroencephalogram refers to the transcription of the recording in the form of a trace. It makes it possible to study and differentiate the main types of brain waves (delta, theta, alpha, and beta).
This painless examination is mainly used to diagnose epilepsy.
Why pass an electroencephalogram?
The electroencephalogram can detect several neurological disorders, related to abnormalities in brain activity.
This examination is especially prescribed in case of suspicion of epilepsy. It is also used:
- To take stock of an epileptic seizure
- To accurately diagnose the type of epileptic syndrome and monitor its treatment
- in case of coma or state of confusion
- after a stroke
- to investigate sleep quality or diagnoses of sleeping sickness (sleep apnea syndrome, etc.)
- to confirm brain death
- to diagnose encephalitis(Creutzfeld-Jacob, hepatic encephalopathy).
The examination is usually performed in a standby state. The patient lies in a recliner chair in a hospital, clinic, or doctor’s office. His head is resting on a foam cushion.
Medical personnel place electrodes on the scalp (between 8 and 21), according to precise positioning. They are fixed with an adhesive conductive paste. The skin of the skull is first wiped with a swab soaked in alcohol.
The recording lasts about twenty minutes. It can also be performed after sleep deprivation or over longer durations, up to 24 hours. It is important to remain calm and still during the exam.
In some cases, anomalies are “triggered”:
- asking the patient to breathe fast and hard (hyperpnea test) for about three minutes
- by exposing it to intermittent light stimulation (ILS), i.e. intermittent flashes with a stroboscopic effect, which can trigger an epileptic seizure or reveal EEG abnormalities
Shampooing is carried out after the examination to remove the adhesive paste.
What results can be expected from an electroencephalogram?
Several abnormalities in brain electrical activity can be detected through EEG.
In the case of epilepsy, for example, the examination will confirm the diagnosis and monitor the effectiveness of the treatment.
The doctor may propose appropriate care and possibly prescribe other tests, such as a brain MRI.
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