No one knows about electricity, but people know little about bioelectricity, in fact, all life activities are accompanied by electrical changes. Without electricity, the heart will not beat, without electricity, the brain will lose consciousness, without electricity, the muscles will lose contraction and diastole, etc. All the physiology, biochemistry and metabolism of the human body cannot be separated from electricity. Doctors through special instruments on the body surface of different parts or organs of the electrical changes recorded on paper, in the form of line diagrams to indirectly respond to the function of organs, this line diagram is called “a certain electrogram”, based on the diagnosis of disease, such as electrocardiogram, which has long been known for the diagnosis of heart disease method. Electromyography can also help the physician to make a qualitative and localized diagnosis of the measured muscle or the neuropathy innervating the muscle. Under normal conditions, muscle contraction and diastole are innervated by nerves. Once a muscle loses its innervation, it is not only unable to complete contraction and diastole, but also atrophies due to lack of nerve nutrition. When a nerve is damaged, the muscle innervated by the nerve will show abnormal electrical potentials and abnormal electromyography, which is used to qualitatively diagnose the nerve damage. The abnormal electromyogram is also seen in the muscle itself, but there is a difference between the two types of abnormal electromyogram, so that neurogenic and myogenic damage can be distinguished. In the case of nerve damage, a specific type of potential – denervation potential – can be recorded on the muscle that has lost innervation in a completely relaxed state; allowing the muscle to contract lightly for activity, no motor unit potential is seen in complete damage, and taller potentials are seen in chronic damage; when the muscle undergoes vigorous contraction, the EMG shows a reduction in the recruitment phase. In contrast, when myogenic muscle atrophy is present, in addition to the same denervated potentials seen in relaxation as in neurogenic damage, motor unit potentials are short and polyphasic waves are increased in light contractions, and an increase in recruitment phases is seen in vigorous contractions. Although CT, MRI and other imaging examinations can clearly show the cranial, spinal and spinal cord structures and have long been recognized for their diagnostic value in neurological diseases, they are inferior to imaging in identifying radicular lesions and peripheral single nerve injuries, in determining the degree of neurological impairment, and even in analyzing the correlation between structural changes and clinical symptoms, which is precisely the value of EMG applications and plays a complementary role to imaging. This is the value of EMG, which complements imaging. Because of the different anatomical decomposition of the motor and sensory nerves in the spinal canal and their paravertebral pathways, EMG in radiculopathy only shows a decrease in motor nerve amplitude, while sensory nerve potentials are not affected, and sensory nerves are affected only if the nerve is stuck behind the posterior root ganglion. This is the key to determining radiculopathy. Root neuropathy also shows simultaneous abnormal potentials in multiple muscles innervated by the same nerve, e.g., in cervical 5 and 6 root lesions, denervated potentials may appear in the deltoid, biceps, infraspinatus, and brachioradialis muscles, all of which are innervated by different single nerves. Once multiple or regional muscles show denervated potentials, root or stem injury should be considered first, rather than single nerve lesions. For example, the H reflex is abnormal in sacral 1 radiculopathy or tibial neuropathy, while the H reflex is not affected in common peroneal nerve injury, so the normal H reflex can identify sacral 1 radiculopathy and common peroneal nerve injury. Thus, electromyography is an examination means to respond to neurological diseases through electrical abnormalities, and it has clear significance especially for the diagnosis of some neurological conditions that are difficult to be determined through clinical analysis. It can make up for the deficiency of imaging in the differentiation of radiculopathy and peripheral single nerve injury, and it can provide the maximum basis in nerve injury to help clinicians to make localized and qualitative diagnosis of nerve injury. Therefore, when you are in doubt about the diagnosis of neuropathy or nerve injury, it is possible that EMG can help you a lot.