All nerve pain/dysfunction/injuries are first evaluated by history and physical examination. A definitive diagnosis can then be made with nerve conduction studies and electromyography (EMG).
When a doctor refers you for an “EMG” study or “nerve test,” you will be undergoing electrodiagnostic testing by a specialized machine. The examiner is usually a physiatrist or neurologist. The study consists of 2 parts, and generally requires 30 min- 1 hr (including set up of equipment, history/physical evaluation, etc.).
The first part of the test is called the “nerve conductions,” which involves electrically stimulating your peripheral motor and sensory nerves, usually in the arms or legs, and recording the waveforms that are produced. You should feel a slight electrical shock and may see your muscles twitch, but these electrical impulses are extremely fast and well tolerated by most people.
The second part involves putting a needle electrode (using a very thin needle) into various muscles and recording the electrical activity from them. This provides information about your nerves and muscles.
In general, EMG studies are very well tolerated; and the anxiety is worse than the actual study. The most common potential side effect is mild, temporary pain/bruising at site.
Common diagnoses from EMG:
peripheral nerve injuries, nerve compressions (i.e., carpal tunnel syndrome), cervical/lumbar radiculopathy, plexopathies, peripheral neuropathy.
Contraindications to EMG
- Active infection at the site.
- Extra precautions must be taken with: patients on coumadin or other anti-coagulants, patients with hemophilia or other blood dyscrasias, patients who are HIV-positive, or patients with a cardiac pacemaker, neuromodulatory implant or transcutaneous stimulator.
- Patient refusal. Patient effort is always an important component in the EMG portion of the exam; it is relatively easy to tell if pt is giving full effort or not (by muscle recruitment pattern).