Secondary epilepsy is relative to primary epilepsy, which is hereditary epilepsy. Therefore, except for hereditary epilepsy, all epilepsy can be called secondary epilepsy, regardless of whether it is secondary to tumor, trauma, vascular disease, or encephalitis. For secondary epilepsy, the most important diagnosis is divided into three steps: 1. whether there is epilepsy, secondary epilepsy is a kind of epilepsy, judged as epilepsy before it can be secondary epilepsy; 2. whether there is a cause, the cause has to be found before it can be a secondary cause, of course, other than genetic causes, such as the presence of trauma, the presence of cortical dysplasia, the presence of tumors, metabolic and other immune factors; there are also some that are difficult to find The cause, but we think there is a cause present; 3. Is there a causal relationship between the cause and the seizure, for example, a patient with abnormal sodium ion channels may cause Dravet syndrome, but then the patient suffers from epilepsy due to trauma, we have to analyze whether trauma is the main cause or whether the ion channel itself is abnormal and genetic abnormalities are the main cause. Therefore, the diagnosis is made in three main steps, and in clinical practice, the EEG, imaging, and blood tests are used to determine the presence or absence of etiology, causality, and seizures.