Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons). Motor neurons transmit electrical signals that cause muscles to contract. An EMG translates these signals into graphs, sounds or numerical values that a specialist interprets.
A number of illnesses primarily involve the peripheral portions of the nervous system and/or the muscles. These neuromuscular processes affect various anatomic structures including the cells in the spinal cord from which the nerve roots are derived. Furthermore, the plexus of nerves in the axilla and pelvis, or the individual nerves in arm or leg, controlling the muscles or sensation in the extremities, may be damaged. Lastly, certain disease processes primarily affect either the neuromuscular junction between the nerves and muscles, or the muscles themselves.
EMG is indicated for the evaluation of specific neuromuscular processes including the spinal muscular atrophies such as Werdnig-Hoffmann disease, plexopathies as exemplified by Erb's palsy, congenital or acquired neuropathies including the Guillain-Barre syndrome, or defects in neuromuscular transmission such as myasthenia gravis. Among various myopathies are acquired diseases of the muscles including polymyositis or those of genetic origin, including muscular dystrophies.
Unlike x-rays, CT scanning or MRI’s that illustrate the anatomy or structure, this test shows the functional ability (or disability) of the nerve, muscle or spinal root. EMG gives information that cannot be obtained with a picture or a blood test. The abbreviation EMG stands for Electro (electric), Myo (muscle), Graphy (writing). The test could be considered a close relative of EKG, the electrocardiogram.
This is not a test for sprain syndromes, bone pathology, arthritis, or pain in general. An EMG can be entirely normal in spite of severe pain. It is a diagnostic test to determine the underlying cause of a presumed neurological problem. However, it does not address illnesses of the central nervous system; thus, it is not a test of the brain, and it does not evaluate presence of stroke or multiple sclerosis. The test has no therapeutic benefits and will not by itself lead to any improvements. It is in no way related to acupuncture.
What Is An EMG?
An EMG is actually a two-part test consisting of nerve conduction studies (NCS) and electromyography (EMG).
Initially, the neurologist performs the nerve conduction studies by stimulating the various nerves along their course. Recordings are made from the muscles for motor nerves, or over the nerve itself when testing sensory function. Patients will experience a sensation similar to a mild static charge; perhaps like that from a wool rug in the winter months. The actual speed of nerve conduction can be calculated.
Subsequently, in the electromyography part, the physician inserts a tiny electrode into the muscles. The electrode acts like a microphone allowing us to listen to the muscle's electrical activity. We also observe the responses on a screen similar to a personal computer. At the onset, the patient experiences a tiny pinch. The electrodes are slightly larger in size to those utilized for acupuncture. The physician listens to the responses and observes the screen.
Why Would I Be Referred for an EMG?
- Tingling & Numbness
- Entrapment Neuropathies
- Nerve Injuries
- Carpal Tunnel Syndrome
- Disc prolapse, herniation, or degeneration
- Cranial Nerves e.g. Facial Palsy
- Local Weakness
- Radiating Pains
- Fasciculation, or muscle twitches
During an electrodiagnostic testing, electrodes are placed over nerves, and electrical stimulation is used to measure nerve conduction speed and delays. Later, a needle electrode is inserted into certain muscles to measure electrical activity and wave formation. EMG Tests are extremely useful in localizing pinched cervical and lumbosacral nerve roots.
Is there any special preparation for my EMG?
Take a shower with soap the morning of the test.
Please do not use any oils, lotions, or perfumes, as this can affect the procedure. Leave necklaces and bracelets at home. Have a normal meal and take medications as usual. The test does not leave you impaired: you can drive and work afterwards.
Be sure to tell the physician if you are taking coumadin (Warfarin), Lovenox, daily aspirin, or other blood thinners, or if you have a bleeding or clotting disorder. Please, report any current infections, lympedema, or history of lymph nodes surgery (most often with mastectomy for breast cancer). Presence of pacemaker or heart irregularities is NOT a problem.
How long does the standard EMG test take?
Most EMG tests last about 40- 60 minutes. Please, count on spending one and a half hour in the neurology office. Because we reserve this time for you, if you do not make your confirmed appointment, we are have to charge a "No Show" fee, that is not covered by your insurance.
Should I bring someone for moral support?
Please, do not bring children, unless they are old enough to sit in the waiting room unattended. Your spouse, friend or child is not allowed into the procedure room, unless needed to help you undress and dress.
Is EMG testing covered by insurance?
Yes, almost always insurance will cover EMG testing.
Your primary care physician, orthopedic surgeon, or rheumatologist, or to doctor will usually send a referral with you to Dr. Rosenkilde's office. Please check with your doctor or our office to confirm whether or not the insurance company requires the EMG to be "pre-certified".
Is EMG testing painful?
Dr. Rosenkilde is particularly experienced in this testing. The test is safe and not associated with any significant side effect. He receives many referrals for testing; he always performs the test with extreme care. Yet, an EMG test is uncomfortable, but not greatly so. The patient may experience discomfort because of electrical sensations and/or brief pain from initial needle insertions.
What Is the Test Like?
You will be partially undressed, usually lying flat on your back on the examination table. First part of the test is “nerve conduction velocities” that involves electrical stimulation of a nerve along with the recording of the resulting muscle contraction. The stimulation lasts 1-5 milliseconds (thousands of a second).
It feels “strange,” “bizarre”, “like a tingling” and is only sometimes uncomfortable. Recordings on an computer screen show the health of nerve and muscle based on measures of response latency, amplitude, morphology, and velocity. More than one nerve is examined. Usually right and left sides are compared, but occasionally the test involves arm and leg on one side.
The test will NOT be limited to one side, even though symptoms may be restricted to one limb. The main reason is that any nerve disorder usually (but not always) is present on BOTH sides, although the patient may experience symptoms on one side only. Furthermore, there is a basic need to compare the "good" with the "bad" side. Do not be surprised if the findings of nerve damage do not correlate completely with your symptoms. Not infrequently, worse symptoms are present on the side with fewer electophysiological abnormalities.
The next part of the testing is the EMG, using a recording needle electrode that penetrates the skin overlying a muscle. A series of muscles are examined. The number of penetrations may vary from 8-20 in each limb. Recordings are done while completely relaxing the muscle. At other times, you will receive instructions to move a joint leading to muscle activation and contraction. Any movement should be done gently and gradually, never suddenly or strongly.
Continue the motion until told otherwise by the doctor.
No anesthetics will be administered. You will be fully alert and awake. Some minor bleeding usually occurs. Sometimes a small bump in the skin develops due to slight bleeding inside the muscle, a subcutaneous hematoma. After examination of muscles in the limbs, a few recordings are sometimes done from muscles along the spine. After the exam, you may experience mild tenderness in some muscles for no more than 24 hours. A few spots may be black, blue, green or yellow 5 - 10 days after the test, similar to the occasional findings after blood drawing in your doctor's office.
When Will I Receive the Results of my EMG?
Results will be given at the conclusion of the session. If Dr. Rosenkilde requested the testing, the results will be discussed with you and any one family member that came with you.
However, if you are sent for the test by another doctor, the results will be forwarded to that doctor. The results will NOT be discussed or explained further. The reason is that the testing doctor is not your treating doctor. Thus, you will have to ask the doctor that referred you how to explain findings and how to treat. Some patients have difficulties understanding this method, although the situation is very similar to testing of EKG or radiographic imaging: results are reported by a doctor, but you, as a patient, will discuss the findings with the ordering and treating doctor.
Are there any risks to having an EMG?
EMG is a low-risk procedure, and complications are rare. There's a very small risk of bleeding, infection and nerve injury where a needle electrode is inserted. When muscles along the chest wall are examined with a needle electrode, there's a very small risk that it could cause air to leak into the area between the lungs and chest wall, causing a lung to collapse (pneumothorax).