EMG tests the function of an isolated nerve supplying a specific muscle, by recording directly from that muscle. There is no external stimulation.  The recording is performed by inserting a very fine needle into the muscle and the patient is then asked to contract and relax that muscle. As this test relies on the patient’s participation, it cannot be performed under anaesthesia. EMG is used in the diagnosis of nerve-root compressions, muscle diseases and in assessing the severity of a nerve injury or disease in the acute or chronic stages. Typical symptoms requiring EMG include muscle weakness, wasting or abnormal muscle twitches
This study can be uncomfortable and may result in minor bruising and tenderness afterwards. If performed, EMG is always performed after NCS and never in isolation