An EEG (electroencephalogram) is a medical test that measures the electrical activity of the brain using small metal discs called electrodes that are attached to the scalp. During the procedure, the electrodes are connected with wires to an instrument that amplifies the brain waves and records them on computer equipment. EEG results show changes in brain activity that may be useful in diagnosing brain conditions, especially epilepsy and other seizure disorders. EEG can also help diagnose or treat brain tumors, brain damage from head injury, brain dysfunction from various causes, inflammation of the brain, sleep disorders, and stroke. An EEG is usually carried out by a highly trained specialist, called a clinical neurophysiologist, during a short visit to the hospital. EEGs are safe and painless, and the procedure is completely non-invasive.