What is an electroencephalogram? EEG is a modern adjunctive test that uses an EEG scanner to record the spontaneous, rhythmic electrical activity of brain cell populations and amplify the brain’s own weak bioelectricity into a graph through an EEG recording device to help diagnose disease. The electrodes are usually placed on the surface of the scalp to detect the electrical activity of the cells in the brain, and doing an EEG is not to electrify or click the body, and will not cause discomfort or harm to the patient. EEG is a common clinical test that can be repeated many times without harm to the patient. Why is it important to have an EEG for epilepsy? The EEG is one of the most important tests in the diagnosis of epilepsy. It is used to determine whether a patient’s condition is a seizure and to identify the type of seizure, possible epilepsy syndrome, and to help identify triggers of epilepsy. indicated seizure medication; assessing the presence or absence of surgical indications and determining the site of seizure origin; looking for the cause of impaired cognitive function; determining whether clinical behavioral changes are non-convulsive persistent; and assessing the risk of recurrence after withdrawal of antiepileptic drugs. When is an EEG usually performed? The conditions in which an EEG should be applied include: 1. The first visit, in order to determine if it is epilepsy. This is when an EEG is needed to confirm whether it is epilepsy, what type of epilepsy, and to provide clues about medication. 2. When you have been taking medication for a period of time, your epilepsy is well controlled and you are ready to stop taking it. In this case, an EEG can provide evidence to determine the chance of recurrence after stopping the medication. 3. Before preparing for surgery for refractory epilepsy. The EEG is used to determine if surgery is possible and to locate the location of the epileptic lesion. What are the categories of EEG tests? EEG is divided into three major categories: conventional EEG, dynamic EEG, and long-range video EEG. Conventional EEG Because of the great randomness of epileptiform discharges, conventional EEG usually takes about 20-40 minutes to record, and it is often difficult to capture epileptiform discharges, so the usage rate is decreasing year by year. Ambulatory EEG is called portable EEG monitoring and can usually record continuously for about 24 hours, so it is also called 24-hour EEG monitoring. Since there is no video equipment, it is mainly used for people with relatively infrequent seizures, whose seizures are not easily captured by short-range EEG recordings, or those whose seizures are already under control and are to be reviewed before or after complete withdrawal from antiepileptic drugs (monitoring time is long and sleep deprivation is not required). Long-range video EEG is a synchronized video device added to the EEG equipment so that the patient’s clinical situation is captured simultaneously. The monitoring time can be flexible depending on the condition of the equipment and the needs of the patient, ranging from a few hours to several days, during which most patients can record a complete wake-sleep-wake cycle. Since the EEG activity is recorded while the patient’s state is collected at the time, excluding relevant interfering factors, it is more accurate and reliable than dynamic EEG and can be used as a localization test before epilepsy surgery. It is the most accurate of the scalp electrodes and is relatively more expensive. In addition to scalp electrodes, the Tangdu Epilepsy Center also uses pterygoid electrodes, intracranial cortical electrodes (surface of the brain), and deep electrodes (deep brain). The intracranial electrodes need to be installed surgically and are the “gold standard” for epilepsy surgery, which effectively improves the accuracy of epileptic lesion localization and greatly increases the chances of successful surgery. The EEG is a safe test, and the test is not harmful to the patient, and can be repeated as many times as needed. The electrodes placed on the scalp to receive bioelectric activity are not energized and the patient will not feel discomfort. The whole body muscles are relaxed to avoid myoelectric interference, and the eyes are opened, closed or hyperventilated as requested by the physician. Hair may need to be shaved if it interferes with the placement of the electrodes and the test results, generally short hair under 2 cm requires shaving. The EEG may change over time, so the EEG may be repeated several times as needed.