There are many types of preoperative tests for epilepsy. The primary tool is the EEG. In the past, EEG could only detect epileptic waves, but now there are significant developments, such as long-range EEG, video long-range EEG, and stereotactic EEG. Among them, video long-range EEG is a combination of EEG monitoring system and video recording device to record the clinical performance and EEG of the patient at each time period (including seizures) simultaneously. Doctors can accurately grasp the patient’s activity status and corresponding EEG changes in each time period, identify epilepsy and initially locate intracranial focal areas. Gu Shuo, Department of Neurosurgery, Shanghai Children’s Medical Center Stereotactic EEG, also known as stereotactic-electrode EEG, is a minimally invasive method with the help of surgery. It involves stabbing probes into different parts of the inner brain and recording EEG at the target point during the interictal period (i.e., when there is no seizure) and during seizures to pinpoint the lesion. This method detects lesions deep within the skull such as the cerebral sulcus and gyrus, and provides an understanding of the depth and breadth of the lesions. The second major tool is imaging, represented by MRI. It can detect morphological and structural problems in brain tissue, especially in the developing cerebral cortex. Again, there is magnetoencephalography. Epilepsy is caused by abnormal discharges in the brain, and the EEG looks into the different currents sent by each cell. And where there are currents, there is a magnetic field. Therefore, by detecting the magnetic field, magnetoencephalography can also locate the origin of abnormal brain waves. Since the magnetic field is not obstructed by the skull, scalp, etc., the final deviation may be less than 1 mm and its results are more accurate. However, this method is expensive, complicated to perform, requires the physician to exclude outside interference, and must be performed in a completely isolated and closed room, so its clinical use is lower than that of EEG. Finally, PET-CT and SPECT are used to detect the functional activity of brain cells. The most used of these methods are EEG and MRI. If these two methods cannot be accurately localized, only then will additional tests such as magnetoencephalography and PET-CT be considered.