Electrodiagnostics refer to a variety of specialised testing that may be required in order to evaluate an injury, define symptoms, or help to diagnose specific muscular or neurological disorders. The two main types of electrodiagnostic testing performed are electromyography (EMG) and nerve conduction studies (NCS).
Electromyography means the electrical recording of muscle activity (myo=muscle). The muscles of the human body generate electricity as they move. When a muscle is at rest, there is no discernible electrical activity. However, when a muscle moves, there is measurable electrical activity.
During an EMG test, a needle is inserted through the skin into the muscle. The needle is connected to equipment (an oscilloscope) that can identify and chart electrical activity. The patient is asked to move or contract various muscles, while the EMG equipment records muscle activity. In a standard EMG test, the reading is taken when the needle is inserted, when the muscle is at rest, and when the muscle is completely contracted.
Results from the EMG study may reveal whether the nerves supplying a particular muscle hor whether the muscle fibres themselves may have been damaged.
An EMG study may be performed whenever some degree of neurological damage is suspected. Diagnosis rarely depends solely on EMG test results, but the EMG study may be an important component of the diagnostic procedure.
Nerve Conduction Study (NCS)
The nerves of the body respond to electrical energy. During an NCS test, electrodes are adhered to the surface of the skin along a particular nerve pathway. Gentle electrical energy is supplied to one electrode and the speed at which this energy can be conducted along the nerve pathway is measured. An NCS study usually displays study results on a computer using specialised software.
The purpose of an NCS study is to determine if nerves in the body have been damaged or may be dysfunctional. A properly conducting nerve pathway should transmit the electrical signal quickly. A damaged nerve will conduct slowly or not at all.
An NCS test can diagnose nerve and neurological damage in specific nerve pathways. It is used for a variety of neurological disorders.