Many epileptic individuals have normal EEGs between seizures. An abnormal EEG indicates that I have epilepsy. Many persons who do not experience seizures have modest EEG abnormalities. A clinical diagnosis is one that is determined based on a patient's history and examination. An EEG cannot make this diagnosis. An electroencephalogram (EEG) is the recording of the electrical activity within the brain. It is useful in diagnosing epilepsy, evaluating its severity, and determining which parts of the brain are responsible for certain symptoms such as blindness, confusion, or loss of consciousness. An EEG can also help identify other conditions that may be causing or contributing to seizures, such as acute trauma to the head, infection, vitamin deficiencies, drugs, and alcohol. The two main types of EEG recordings are standard EEG and video-electroencephalography (v-EEG). Standard EEG records the entire brain at one time; it is used to diagnose neurological disorders and to monitor patients during sleep or anesthesia. Video-EEG records selected portions of the brain while watching television or a movie; it is used to locate the source of seizures. Other types of examinations that may be performed along with the EEG include magnetic resonance imaging (MRI), computerized tomography (CT) scans, and neuropsychological testing. Standard EEG recordings use multiple electrodes placed on the scalp in accordance with the 10-20 system.