Nerve conduction studies/ EMG
Nerve conduction studies and electromyography are tests to help diagnose diseases of nerves and muscles. A NCS/EMG test is tailored to your specific complaint and the diagnostic question of the referring physician. The test does not treat your condition. Both tests are performed together to help to localize the area of involvement causing your symptoms. A normal NCS/EMG usually lasts 30-60 minutes. There is no lasting effect from the test.
The test involves two parts:
1. Nerve conduction studies (NCS)
Are used to test individual nerves. Peripheral nerves are organs that serve as the “wiring” carrying signals for sensation, muscle commands, and other special functions to and from the brain and spinal cord. The nerves tested travel in predictable routes through the body, well known to each examiner. Testing involves stimulating a nerve with brief, small electrical impulse to the skin surface and recording the response from a muscle or another portion of the nerve via small detection pads on the skin. The electrical stimulations range from barely perceptible to a shock comparable to a static electric shock in winter. These studies are very safe and even the maximal machine output is too small to cause injury. Most studies require only a small fraction of the maximal level. There are no lasting effects. Information on the health of each nerve including the location and type of specific nerve injury is gathered and interpreted.
Recording electrodes are applied to the muscle being examined. The nerve is then stimulated with a small electric current. You might feel a tingle or your muscles may twitch. You should wear loose clothing and avoid using any skin lotions prior to the test.
2. Electromyography (EMG)
Is another type of testing providing complimentary information, usually following nerve conduction studies. In this test a sterile, disposable, very thin needle electrode (about the width of a straight pin (26 gauge)), Teflon coated to ease insertion is placed through the skin into a muscle. The needle is a specialized recording device with a fine internal platinum wire, analogous to an antenna that directly records the muscle’s natural electrical activity at rest and during muscle contraction. Analysis of this activity gives important information about the health of each muscle tested as well as the controlling nerves. Each examination is specially tailored to provide information about the specific clinical questions for a given patient.
A sterile needle electrode is inserted into a muscle to “listen” to the electrical activity while you contract and relax the muscle. Nothing will be injected. You will feel the poke of the needle.