Do I have to have a seizures in order to detect abnormal brain waves?

Abnormal EEG. Not exactly, in seizures there is an ictal and interictal state. Ictal state means during active seizure which shows the typical type of abnormal eeg related to the seizure type. Interictal state is an abnormal waves without active seizure, it shows that the brain is active and means an increased risk of seizure. It means that you don't have to have active seizure at the time of eeg to have abn.