An EMG assess the electrical activity of a nerve root and is sometimes recommended for patients with back pain. An electromyograph detects the electrical potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement.
Needle EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions includeamyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.
After three weeks of pressure on a nerve root, the muscle the nerve goes to will begin to spontaneously contract. Compression of a nerve will also slow electrical conduction along that nerve. EMG’s are also sometimes useful to distinguish nerve degeneration (neuropathy) from nerve root compression (radiculopathy).
The test involves placing small needles into the muscles, so there is some discomfort for the patient. There are no major risks, although the tests are not highly reliable in determining which nerve is compressed.
