NERVE CONDUCTION STUDIES / EMG
EMG (electromyography), or nerve conduction study, is an electrical test that measures how well nerves and muscles work. Its main application is in the diagnosis of the following disorders:
- Focal disorders of nerves, such as carpal tunnel syndrome
- Nerve root disorders, such as pinched nerves in the neck or back from a herniated disc or spinal stenosis
- Diffuse nerve disorders, such as peripheral neuropathy from diabetes or other conditions
- Certain specific neuromuscular disorders, such as amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) and myasthenia gravis
- Disorders of muscle, such as polymyositis and muscular dystrophy
The test may take one hour or longer in more extensive cases to do. It consists of two parts:
- Nerve conduction studies: Applying controlled electrical impulses to specific nerves, and measurement of responses.
- EMG Needle electrode examination: Inserting a fine needle into different muscles of one or more extremities.
Relative contraindications to the test are:
- A bleeding tendency, such as from the use of a blood thinner such as Coumadin (Warfarin) or Heparin, or from advanced liver disease. Patients on Coumadin are advised to stop taking Coumadin three days prior to the test, and resume taking it immediately after the test, if permitted by their primary physician. The use of aspirin or aspirin-like medications (such as Plavix or Aggrenox) is not a contraindication to the test.
- An implanted cardiovertor defibrillator device (ICD), however, a pacemaker is not a contraindication.
Specific instructions for patients:
- Take a shower on the morning of the test and specifically thoroughly clean the extremities to be tested with soap and water.
- DO NOT apply oil, lotion or cream to the extremities to be tested.
- If the weather permits, wear a short-sleeve shirt or blouse (for the arm) or shorts or a skirt (for the leg).