Electroneurographic examination (electroneurography (ENG)) is a method of determining the nerve conduction velocity of peripheral nerves in neuronal and/or muscular diseases. In the majority of cases, electroneurography is unproblematic and not associated with any complications.
What is electroneurography?
Electroneurography is the name given to a diagnostic procedure in which the nerve conduction velocity of potentially damaged nerves is determined. Electroneurography (ENG) is the name given to a diagnostic procedure in which the nerve conduction velocity (NLG) of potentially damaged nerves is determined. Electroneurography is generally used when there is a suspicion of disease or damage to the peripheral nervous system, i.e. the motor and/or sensory nerves in the head, trunk and/or limbs. In addition, electroneurography is used for monitoring the course as well as differential diagnostic classification of various neuronal and muscular diseases. Impairment of nerve conduction velocity can be detected, among other things, as a result of a pinched nerve (e.g. carpal tunnel syndrome in the wrist) or a polyneuropathy and manifests itself in particular in the legs and arms by means of sensory disturbances (e.g. numbness, tingling, hands and legs falling asleep). Depending on the outgoing question as well as the neuronal anatomy, electroneurography may require determination of the nerve conduction velocity of several nerves.
Function, effect, and goals
During an electroneurography, the functional capacity of the sensory and motor nerves is determined and monitored. While motor nerves are responsible for regulating and controlling movement and transmitting stimuli sent by the brain to the corresponding muscles, sensitive nerves send auditory, haptic, and visual sensory input to the brain. To determine the conduction velocity of motor nerves, different surface electrodes, so-called stimulus and conduction electrodes, are applied to the skin at a distance to be measured in advance in the area of the nerve to be examined. Subsequently, the nerve of interest is stimulated several times (at least twice) via the stimulus electrodes by a weak and short electrical impulse and the time required to transmit this stimulus to the lead electrode is measured. The nerve conduction velocity, which is only a few thousandths of a second in the normal state, is calculated from the distance between the stimulus and the lead electrodes and the determined time. To determine the sensitive nerve conduction velocity, in an electroneurographic examination either a needle electrode is pierced into the muscle innervated by the nerve to be examined, or the nerve to be controlled is electrically stimulated by surface electrodes, while in turn a conduction electrode measures the reaction time. The nerve conduction velocity determined in this way allows conclusions to be drawn about damage and pathological changes in the nerves under investigation as well as about neurological diseases. For example, a prolonged nerve conduction velocity can indicate the presence of carpal tunnel syndrome (also median compression syndrome) or polyneuropathy (damage to peripheral nerves) as a result of diabetes mellitus (diabetic neuropathy) or another chronic metabolic disease. Accordingly, electroneurography can also be used to determine the need for therapy modification in generalized metabolic diseases. In addition, electroneurography allows statements to be made as to whether the axon (conducting extension of a nerve cell or nerve axis) itself or the myelin sheath (insulating medullary sheath) of the nerve is damaged. In addition, in many cases the exact location of the damage can be localized and the extent of the structural neurological damage can be determined. Electroneurography also enables the diagnosis and monitoring of muscular diseases. If damage to muscular structures is suspected, electromyography is used in parallel with electroneurography to assess muscle activity.
Risks and side effects
In all cases, electroneurography is not associated with any risks or serious complications.Even so-called anticoagulants, blood-thinning drugs such as Marcumar, Heparin, Rivaroxaban or Acetylsalicylic Acid (ASS) do not preclude an electroneurographic examination. The electrical stimuli used in electroneurography are often perceived as unpleasant and/or painful by the patient being examined, depending on the underlying neurological disease. In addition, after an electroneurographic examination, sensory disturbances such as tingling or numbness may be observed. These are usually harmless and disappear by themselves after a short period of time. In addition, it should be noted that electrical impulses can cause irritation in pacemakers. Appropriate precautions are indicated for persons wearing a pacemaker. Under certain circumstances, electroneurography may be contraindicated, so that other diagnostic procedures should be used. Furthermore, when thin needle electrodes are used during electroneurography, pain comparable to that experienced during a blood draw or injection may occur.
