An EMG is a recording of the electrical activity (nerve response) of muscle tissue at rest and during activity. During an EMG, a physician will clean the skin over the muscle to be tested, then insert one or more needle electrodes into the muscle. The electrode is attached to a recording machine by wires and measures your muscle's electrical activity. An NCS is a surface recording of a nerve response produced by a small electrical stimulus applied a short distance away. The NCS is performed by a physician or technician and assess the size and speed that electrical signals are transmitted through your nerves.
Most patients will have both an EMG and NCS performed during the same visits. Typically this takes up to 2 hours to complete, though your exam may take more or less time depending on what’s been ordered. These tests are often used distinguish between a muscle disorder and a nerve disorder, helping your healthcare team to diagnose, rule out or treat certain neurological conditions, such as:
Brachial plexus injury
Carpal tunnel syndrome
Amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease
At the end of your test, the physician will briefly summarize the test results before they prepare a formal diagnostic report.