Making a Back Pain Diagnosis: Nerve Tests

Nerve tests, also called electrodiagnostic studies, are used to determine whether the source of nerve deficits or changes in the arm, buttocks, or legs are a result of nerve compression in the peripheral nervous. The brain and nerves traveling along the spinal cord are part of the nervous system, and the nerves become part of the peripheral nervous system once they leave the spinal cord. These studies predominantly are designed to tests the nerve roots where they exit the spinal cord. These nerve tests, if possible for nerve root compression, may lead to a diagnosis of a herniated disc or spinal stenosis. Both of these back conditions include symptoms such as:
  • Pain that is sharp, debilitating and travels down one leg (herniated disc).
  • Tingling, weakness, numbness in legs (spinal stenosis).
  • Pain in the buttock, leg or thigh when walking or standing (spinal stenosis).
Electromyography is the most common electrodiagnostic test used in back pain.

Electromyography: Electromyography (also called a myogram or EMG) is a procedure where muscle activity and strength and the contractions of the muscles are observed by either placing sensors on the surface of the skin or into the muscle(s) b to be observed. The electrical activity of the muscles are then observed on a computer screen or a piece of equipment called an oscilloscope that resembles a TV screen with wavy lines crossing it.

The shape, size, and presence of the waves output on the screen tell the physician how your muscle is to respond to nerve stimulation and can assist in the diagnosis of problems involving the nervous system. The procedure may be somewhat uncomfortable or painful, but it is low risk, though you may feel a little uncomfortable after the procedure. You may feel mild to moderate pain during the procedure. If you are scheduled for a nerve test EMG, you may plan your schedule so that you will have time to rest afterwards before you go home. You may take some ibuprofen or acetaminophen with you to the procedure to relieve some mild pain felt afterwards. If you are already taking back pain medication, check with your doctor to see what you should take immediately following this procedure. If on the day of your procedure, you experiencing lingering moderate to severe pain after taking over the counter meds, contact your doctor's office to see if there is some stronger they can provide you in the short term to feel some relief. Nerve tests such as electromyography are used to determine whether problems with the nerve roots are the cause of pain, weakness, or loss of sensitivity in the legs, and if so, what nerve roots are involved. This test probably won't be ordered if the patient is experiencing symptoms of back pain in the legs alone.

Electromyography detects the electrical potential generated by cells, when at rest and when the muscle is active or being contracted. The cell activity in the muscle or muscles near the location where the sensors are placed may be neurologically or electrically activated. These signals can be observed and analyzed to detect abnormalities in the skeletal muscle, or a lack of muscle activity due to problems with the nerves sending signals to that muscle.