Electroneurography

An electroneurographic examination (Electoneurography (ENG)) is a method for determining the nerve conduction speed of the 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?

As Electoneurography (ENG) is a diagnostic method in which the nerve conduction velocity (NLG) of potentially damaged nerves is determined.

Electronurography is usually used when there is a suspicion of diseases or damage to the peripheral nervous system, i.e. the motor and / or sensory nerves in the head, trunk and / or limbs area. In addition, electroneurography is used for progress monitoring and differential diagnostic allocation of various neuronal and muscular diseases.

An impairment of the nerve conduction velocity can be determined, among other things, as a result of a pinched nerve (including carpal tunnel syndrome in the wrist) or a polyneuropathy and manifests itself in particular in the legs and arms through sensitivity disorders (including numbness, tingling, hands and legs falling asleep).

Depending on the initial question and the neural anatomy, it may be necessary to determine the conduction velocity of several nerves during electroneurography.

Function, effect & goals

As part of a Electroneurography the functionality of the sensory and motor nerves is determined and controlled. While the motor nerves are responsible for regulating and controlling the movement sequences and forwards the stimuli sent by the brain to the corresponding muscles, the sensitive nerves send auditory, haptic and optical sensory impressions to the brain.

To determine the conduction velocity of motor nerves, different surface electrodes, so-called stimulus and discharge 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) by a weak and short electrical impulse via the stimulus electrodes and the time required to pass this stimulus to the recording electrode is measured.

The nerve conduction speed is calculated from the distance between the stimulus and recording electrodes and the determined time, which in the normal state is only a few thousandths of a second. To determine the sensible nerve conduction velocity, in an electroneurographic examination either a needle electrode is inserted into the muscle innervated by the nerve to be examined, or the nerve to be controlled is electrically stimulated by surface electrodes, while a recording electrode measures the reaction time.

The nerve conduction velocity determined in this way allows statements to be made about damage and pathological changes to the nerves being examined as well as about neurological diseases. For example, a prolonged nerve conduction velocity can indicate the presence of a carpal tunnel syndrome (also median compression syndrome) or a 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 necessary modification of therapy in generalized metabolic diseases. In addition, electroneurography enables statements to be made as to whether the axon (conductive extension of a nerve cell or nerve axis) itself or the myelin sheath (insulating myelin 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 determined. Electronurography also enables the diagnosis and monitoring (progress monitoring) of muscular diseases. If there is any suspicion of damage to muscular structures, electromyography is used in parallel to electroneurography, which allows an assessment of the muscle activity.

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Risks & side effects

Usually one goes Electroneurography with no risks or serious complications. So-called anticoagulants, blood-thinning drugs such as marcumar, heparin, rivaroxaban or acetylsalicylic acid (ASA) do not exclude an electroneurographic examination.

The electrical stimuli used in electroneurography are often perceived as unpleasant and / or painful by the patient to be examined, depending on the underlying neurological disease. In addition, after an electroneurographic examination, abnormal sensations or sensitivity disorders such as tingling or numbness can be observed.

These are usually harmless and resolve on their own after a short period of time. In addition, it should be noted that electrical impulses can cause irritation in pacemakers.

Appropriate precautionary measures are indicated for people who wear a pacemaker. Under certain circumstances, electroneurography may be contraindicated, so other diagnostic methods should be used. When using thin needle electrodes during electroneurography, pain can also occur that is comparable to that of a blood sample or injection.