Magnetic resonance imaging (MRI) is a noninvasive scanning technology that uses a powerful magnetic field and radio waves to generate digital images of organs, soft tissues, bones, and other internal body structures. The level of detail in MRI images allows the physician to more accurately evaluate these structures to determine the presence of certain factors, such as inflammation, that are related to disease. MRI scans of muscles are especially useful in helping the physician identify the best site to perform a muscle biopsy.
MRI does not use the kind of ionizing radiation used in x-rays or CT scans, so there is no danger of excessive radiation exposure. The magnetic field is not harmful, but it may cause some medical devices, such as pacemakers or insulin pumps, to malfunction. Most orthopedic implants pose no risk, but you should always tell the technician performing the procedure if you have any devices or metal in your body. Unless you are told otherwise, you should continue taking your regular medications. Do not wear jewelry, but do wear loose, comfortable clothing. You may be asked to wear a gown during the procedure.
The procedure requires that you lay very still inside a tunnel-like tube for 30-90 minutes. During the procedure, you will hear loud clicking noises. If you are claustrophobic or anxious, you may want to ask for a mild sedative before the procedure starts. The technician will let you know how to signal staff if you feel you need to come out of the scanner for any reason.
MRI scans are interpreted by specially trained physicians and the results reported to your doctor who will discuss them with you. If you still have questions after your doctor has explained your MRI results, be sure to ask.
You can watch a video of an MRI here.
Electromyogram (EMG) is a test that measures the activity of the muscles. The test gathers information about both the muscular and nervous systems and is most helpful in determining if muscle weakness and pain are caused by muscle disease or nerve disease. EMG can also be helpful in identifying the muscle group that is most likely to provide useful information on biopsy.
An EMG can be done in a doctor’s office, hospital, or lab. It usually takes about 30-60 minutes, depending on the number of muscles to be tested. A thin metal needle is inserted through the skin into one muscle at a time to record the electrical activity in the muscle. You will be asked to relax the muscle and then contract the muscle after the needle is inserted. The needle is connected to a computer that helps the doctor determine whether your muscle is healthy or affected by a disease of the muscle or nerve. The number of muscles to be tested varies depending on your symptoms and what is found during the actual test.
Nerve conduction velocity (NCV) studies may be done at the same time as the EMG in order to rule out a nerve disease or injury that may be affecting the muscles. For this test, electrodes are placed on the skin to measure the activity of the nerves.
Some people report feeling discomfort or pain, depending on the muscles being tested. If you are extremely nervous, you may want to ask for a sedative before the EMG test.
After the test, you may have mild aching for up to six hours, followed by soreness and tingling in the muscle that was tested for one or two days. You may also have a small bruise that lasts for a week or more. If pain lasts longer than two days, heat can be applied to the test site with a warm compress. Be sure to let your doctor know if you have severe or long-lasting pain.
There are patterns of electrical abnormalities in nerves and muscles that can indicate the presence of an inflammatory disease. The physician who does the test will interpret the results and report them to your doctor who will discuss them with you. If you still have questions after your doctor has explained your EMG/NCV results, be sure to ask.
You can watch a video of an EMG here.