EMG / ENG
EMG
In electromyography (EMG) muscle activity based on its occurring electrical currents is being measured. With the EMG, a distinction can be made to the causative disease. An EMG is performed when either a muscle disease or a nerve injury where a muscle weakness occurs is being suspected. The question whether the disease is caused muscular (myopathy) or nervous (neuropathy), can be clarified by the investigation.
There are many possible causes of muscle and nerve disorders. Both myopathies (muscle disease) and neuropathy (nerve disease) may be hereditary or caused by other circumstances. The latter include, for example, inflammation, metabolic diseases, diabetes mellitus (sugar disease) or hyperthyroidism, autoimmune diseases (diseases in which the immune system attacks the body's own cells) and for the body poisonous substances such as alcohol or drugs. A nervous breakdown can even occur after an injury.
The principle of the EMG is to record the small electrical currents that are generated in all muscle tension. These typically show a characteristic pattern. In various muscle and nerve disorders, certain changes in these emotions are being revealed.
Anaesthetization is not necessary for the EMG; children can be given a sedative drug, for example.
To examine, a thin needle electrode is inserted after disinfection of the skin into a muscle. The thickness of the electrode is only 0.3 to 0.6 millimeters. What muscle is selected for EMG depends on the symptoms and the suspected disease. First, the activity of the muscle at rest is determined, then while the patient tenses the muscle. Sometimes, several different areas of the same muscles or muscle have to be investigated. Also, the needle electrode are pushed or pulled more often, in order to achieve different depths of investigation.
In some cases, an EMG can be performed via skin electrodes, which do not need to be inserted into the tissue.
ENG
The electrical neurography (ENG) is a study of nerve conduction. This helps determine the speed with which a nerve transmits electrical signals (conduction velocity of the nerve). It also measured how well an electrical nerve stimulation on the corresponding muscle is transferred (neuromuscular conduction).
While determining the nerve conduction, the nerve to be examined will be electrically stimulated at least at two places in its course. The time that elapses from the nerve stimulation to reaction (contraction) of the corresponding muscle is measured. The muscle contraction is registered with the aid of surface electrodes by a computer.From the difference of conduction times and the route between the two places, the stimulation of nerve conduction velocity (NCV) is calculated. The determination of the nerve conduction velocity is important for the diagnostic section of nerve compression syndromes (eg Karpaktunnelsyndrom).