Electrodiagnostic Testing (EMG & NCS)
At Texas Orthopedics, patients with peripheral nerve damage, numbness, or pinched or compressed nerves will typically have an electromyography (EMG) and/or nerve conduction study (NCS) ordered to aid in the diagnosis of nerve-related pain. These tests evaluate how your nervous system, brain, and musculoskeletal system work together.
Electromyography (EMG) measures the nerve impulses in muscles during contraction. Doctors use EMGs to identify muscle function as related to nerve input. EMGs help doctors diagnose neuromuscular disease, neurological disorders, muscle disease, and nerve abnormalities associated with pain or numbness.
To begin, a fine needle electrode is placed through your skin and into the muscle that a nerve controls. The electrode transmits information about the nerve and muscle electrical activity. Computer records are taken at rest and during muscle contraction.
EMG may be slightly uncomfortable during the test, and your muscles may remain a bit sore following the procedure. It is common for EMG and nerve conduction studies to be administered at the same time.
Nerve Conduction Study (NCS)
A nerve conduction study measures how well a nerve works and helps to specify the site of nerve compression. Many conditions, such as tissue swelling, injury, and disease can put pressure on a nerve and impair its ability to function. Doctors use nerve conduction studies to help identify nerve problems and plan treatments.
Nerve conduction studies are fast outpatient procedures. To begin, measurements are made and marked on your skin. Sticky patches with electrodes are placed on your skin over the course of a specific nerve. During the study, a nerve is stimulated in one or several places. A computer measures the time it takes for a message (nerve impulse) to travel from one place to another. The waveform is then analyzed for speed and formation.
Most patients do not find the test uncomfortable. The activation of the stimulator has been described as feeling like static electricity, as when a person rubs their feet on a carpet and then touches another person. If pain is experienced, it will not be continuous and will last a very short time.