Electrodiagnostic procedures include electromyography (EMG), nerve conduction studies, and evoked potential (EP) studies. EMG assesses the electrical activity in a nerve and can detect if muscle weakness results from injury or a problem with the nerves that control the muscles. Very fine needles are inserted in muscles to measure electrical activity transmitted from the brain or spinal cord to a particular area of the body. With nerve conduction studies the doctor uses two sets of electrodes (similar to those used during an electrocardiogram) that are placed on the skin over the muscles. The first set gives the patient a mild shock to stimulate the nerve that runs to a particular muscle. The second set of electrodes is used to make a recording of the nerve’s electrical signals, and from this information the doctor can determine if there is nerve damage. EP tests also involve two sets of electrodes — one set to stimulate a sensory nerve and the other set on the scalp to record the speed of nerve signal transmissions to the brain.