The whole head is covered with wires. What kind of mysterious examination is this? Learn about EEG in one article

Author: Fang Yanbo Department of Neurological Critical Care, The First Affiliated Hospital of Zhengzhou University

Reviewer: Du Ran, deputy chief physician of the Department of Neurological Critical Care, the First Affiliated Hospital of Zhengzhou University

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"Doctor, what should I do if my child has a convulsion?"

"Let's do an EEG first."

"Ah! What is an EEG? Will there be an electric current? Will it damage the brain?"

"No, EEG is a non-invasive, radiation-free, and relatively safe test that can be performed on infants and pregnant women."

For epilepsy patients, EEG is not unfamiliar. It has important guiding significance for epilepsy diagnosis, treatment and surgery. Today, let us unveil the mystery of EEG.

1. What is an electroencephalogram?

An EEG does not electrify your brain, but uses metal electrodes to monitor the physiological electrical activity of the brain, which is processed by instruments into a waveform report that doctors can analyze. It is similar to an electrocardiogram, but the time and location are different. In simple terms, it is an instrument for observing brain function. It uses special electrodes to record the spontaneous bioelectric activity of brain cell groups, reflecting the functional state of the brain, and is an auxiliary examination method to help diagnose cranial and brain diseases. The currently popular brain-computer interface and artificial intelligence are also developed based on the electrical activity of the brain.

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Depending on the purpose of the examination, EEG can be divided into the following three types.

(1) Conventional EEG: Usually performed in an outpatient clinic, the test takes about 20 minutes. The advantage is that the test report can be obtained on the same day of the visit; the disadvantage is that the positive rate of epilepsy test is low.

(2) Dynamic EEG: After the patient has electrodes placed by professionals in the outpatient clinic, he or she will carry a micro-cassette tape recording device. After confirming that the instrument is working properly, the patient can go home and record the patient's 24-hour full EEG activity in daily life. The advantage is that the person being tested can walk, attend classes, eat, sleep, etc. freely without affecting their daily activities; the disadvantage is that motion artifacts are prone to occur, making it difficult to identify abnormal EEG activity.

(3) Video EEG monitoring: After the patient is hospitalized, the patient's daily activities are recorded using a camera based on EEG monitoring. The advantage is that when playing back the EEG, the doctor can simultaneously observe the patient's activities while observing the brain waves, understand the entire process of epileptic seizures, and identify movement artifacts, which greatly improves the ability to diagnose epilepsy; the disadvantage is that the cost is high and the monitored person's activities are restricted.

2. Which diseases require an EEG?

Electroencephalogram examination is of great significance for the diagnosis and differential diagnosis of epilepsy or some other paroxysmal diseases, especially for the identification of epileptic seizure types and the evaluation of therapeutic efficacy. It is even of great help in the preoperative evaluation and localization of some refractory epilepsy.

In addition to epilepsy, doctors also need to check EEG when they suspect that the patient has the following conditions, including encephalitis, brain injury, anoxic encephalopathy, metabolic encephalopathy, brain tumors, sleep disorders and coma.

3. What preparations need to be made before the examination?

(1) Wash your hair the day before the examination to ensure that the scalp surface and hair are clean. Avoid using styling products such as hairspray and gel.

(2) Do not stay up late before the examination, make sure to get enough rest, eat a good breakfast on the same day, and do not take stimulant drugs or drinks.

(3) Before the examination, the patient or family members should inform the doctor who performs the EEG of their medical history; especially those with a history of epileptic seizures must tell the doctor in advance. It is generally not necessary to stop taking anti-epileptic drugs (unless there is a special doctor's order).

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4. What should you pay attention to during the inspection?

(1) Turn off mobile phones, tablet computers and other communication devices or do not bring them into the examination room.

(2) You need to remain quiet and relaxed during the examination.

(3) Cooperate with the doctor and follow the doctor's instructions to perform eye-opening, eye-closing, breathing-increasing or sleep tests, etc.

(4) If you sweat a lot during the examination, you should wipe it off immediately.

(5) Do not pull the electrode during inspection.