EMG is the recording of the electrical activity of the muscle. During the test the small needle is inserted in to the muscle and the activity recorded. EMG is done on a patient under deep sedation or general anaesthesia therefore no pain is felt during examination.
Normal resting muscle is generally electrically silent. In abnormal muscle there is spontaneous activity and based on the characteristics of this activity, may tell us the kind of process present in the muscle. EMG helps to confirm the of the existence of the disease of the peripheral nervous system and helps to distinguish between primary nerve and muscle disease. It says precisely if the muscle atrophy is because of disease of the muscle or nerve or because of because of too little activity. In case the nerve(s) of the patient have been damaged during trauma episode, the so called denervation potentials will be detectable on EMG 5 days after trauma. The measurement of the denervation potentials in different muscles will tell the examiner which nerves have been traumatized.