Two types of tests - neurophysiological instrumental tests and coding tests - can be used to investigate the function of the nervous system in clinical practice. Instrumental tests are performed with recording devices that give an image of even residual nervous system functions, in contrast to coding tests, the results of which are determined subjectively and placed on a specific scale. Instrumental tests include classical electrodiagnosis, clinical electromyography, polyelectromyography, ENG or tendon reflex testing, among others.