Febrile seizures are triggered by fever, typically due to a viral infection. They may run in families. The underlying mechanism is not fully known, but it is thought to involve genetics, environmental factors, brain immaturity, and inflammatory mediators. The diagnosis involves verifying that there is not an infection of the brain, there are no metabolic problems, and there have not been prior seizures that have occurred without a fever. Blood testing, imaging of the brain, or an electroencephalogram (EEG) is typically not needed. Examination to determine the source of the fever is recommended. In otherwise healthy-looking children a lumbar puncture is not necessarily required.