Secondary epilepsy is a condition in which various diseases involve the central nervous system, resulting in seizures. Therefore, epilepsy is actually one of the symptoms of the primary disease. Diagnosis and treatment should not only consider epilepsy, but also the treatment of the primary disease. There are many kinds of diseases that lead to secondary epilepsy, briefly listed as follows: I. Brain diseases: 1, congenital developmental abnormalities: commonly found in children; 2, traumatic brain injury or brain surgery; 3, inflammation of the brain: the most common is viral encephalitis; 4, cerebrovascular diseases: including cerebral infarction, cerebral hemorrhage, cerebral arteriovenous malformations, etc.; 5, intracranial tumors; 6, certain hereditary disorders; 7, neurological degenerative diseases: such as Alzheimer’s disease (senile dementia). Second, systemic diseases involving the brain: 1, anoxic encephalopathy: carbon monoxide poisoning, drowning, asphyxia, etc.; 2, metabolic encephalopathy: such as hypoglycemia, hepatic encephalopathy, uremic encephalopathy, etc.; 3, cardiovascular disease: cardiac arrest, hypertensive encephalopathy, etc.; 4, febrile convulsions; 5, eclampsia; 6, poisoning.