The EEG can present as a normal range after taking medication for epilepsy. It is sometimes possible for a person with epilepsy to have a normal EEG even if he or she is not taking medication. This is because when a patient has a seizure, his or her brain waves must be abnormal, but when there is no seizure the brain waves only have a certain probability of being abnormal, and it is possible for a normal EEG to be negative in this case. When the patient is treated with medication and the abnormal brain discharges are controlled, the probability of finding epileptic waves on EEG will be further reduced. To clarify how well the patient’s symptoms are controlled, a 24-hour ambulatory EEG, which is a test that records the patient’s continuous brain waves over 24 hours, should be perfected. Especially in the sleep state, the positive rate of epileptic waves is greater. If the continuous monitoring of 24-hour dynamic EEG is also in the normal range, it means that the patient is well controlled. However, a normal EEG is not a criterion for patients to discontinue medication. It is recommended to take medication for at least 2.5-3 years and review the normal EEG before reducing the dosage, and to reduce the dosage for six months before considering discontinuing the medication.