What is EMG?
EMG is the abbreviation of the term electromyography. It is a muscle examination in which the electrical activity that causes the contraction of the muscles is monitored and interpreted. The contraction of the muscles occurs thanks to the electrical potentials known as Motor Unit Action Potentials (MUAP) created in the muscles by the excitatory potentials transmitted from the brain through the nerves.
The amount of contraction increases with the increase in the number and frequency of MUAPs. Examination of MUAPs in cases where the muscles are not or are contracted, whether their shape or frequency is within normal limits, or electrical activities that are not normally encountered are the variables examined to determine the problems in the muscles. In daily use, EMG examination means a set of tests including nerve examination as well as muscle examination.
What is the Role of EMG in Diagnosing Diseases?
Although EMG does not replace direct examination methods, it guides these methods.
Why is it requested?
EMG and nerve conduction examinations are an indirect method used to diagnose anterior horn cells, nerve roots, nerve networks, terminal nerves, neuromuscular junction and muscle diseases of the spinal cord, respectively, and due to its ease of application, it is often used alone and sometimes with other auxiliary methods (eg, imaging techniques). , blood biochemistry) leads to the most definitive diagnosis or directs the physician to other methods for diagnosis (eg biopsy, direct visualization of the problematic area with surgery). It is often used to measure how much nerve and muscles are damaged in painful situations and sensation defects caused by back and neck hernias, compression of the end nerves at certain points, in some cases where arm and leg weakness are seen, in limited or widespread muscle wasting.
How is EMG done?
Needle electrodes are used in EMG examination for the diagnosis of muscle problems. For this reason, it is also called needle EMG. Usually concentric needles are used. These needles are turned into recording electrodes by placing a very thin wire inside the known injector needles. When a needle attached to the device is first seen, it arouses fear of being electrocuted. However, no electrical stimulation is given in the needle EMG examination. It is used only for recording normal or abnormal electrical activity in muscles. The tip of the needle is inserted directly into the investigated muscle. MUAPs or other electrical activities created by the stimuli sent from the brain for the contraction of that muscle in the muscle area close to the needle tip are amplified by very special amplifiers and monitored on the screen of the device. In addition to the visual examination, the same signals are made audible by the loudspeaker and make a significant contribution to the evaluation of the doctor who performs the examination.