 [ Symptoms ] my sister has attacks with severe headaches and sudden chills then it ends with shivering like fits [ Disease ] this is inevitably epilepsy but a routine eeg only records about 20 30 minutes of brain waves however the entire eeg procedure takes about 90 minutes because 30 minutes is such a short amount of time the results of routine eeg studies are often normal even in people known to have epilepsy did she get a 90 minutes test