Electromyography (EMG) is an electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles. An EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. EEGs detect the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement.
Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include: -Tingling -Numbness -Muscle weakness -Muscle pain or cramping -Certain types of limb pain EMG results are often necessary to help diagnose or rule out a number of conditions such as: -Muscle disorders, such as muscular dystrophy or polymyositis -Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis -Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies -Disorders that affect the motor neurons in the brain or spinal cord, such as amyotrophic lateral sclerosis or polio -Disorders that affect the nerve root, such as a herniated disk in the spine
When the study is underway, the surface electrodes will at times transmit a tiny electrical current that you may feel as a twinge or spasm. The needle electrode may cause discomfort or pain that usually ends shortly after the needle is removed. During the needle EMG, the neurologist will assess whether there is any spontaneous electrical activity when the muscle is at rest — activity that isn't present in healthy muscle tissue — and the degree of activity when you slightly contract the muscle. He or she will give you instructions on resting and contracting a muscle at appropriate times. Depending on what muscles and nerves the neurologist is examining, he or she may ask you to change positions during the exam. If you're concerned about discomfort or pain at any time during the exam, you may want to talk to the neurologist about taking a short break.
When you schedule your EMG, ask if you need to stop taking any prescription or over-the-counter medications before the exam. If you are taking a medication called Mestinon (pyridostigmine), you should specifically ask if this medication should be discontinued for the examination. It is recomended that you take a shower or bath shortly before your exam in order to remove oils from your skin. Don't apply lotions or creams before the exam. You'll likely be asked to change into a hospital gown for the procedure and lie down on an examination table. To prepare for the study, the neurologist or a technician places surface electrodes at various locations on your skin depending on where you're experiencing symptoms. Or the neurologist may insert needle electrodes at different sites depending on your symptoms.
You may experience some temporary, minor bruising where the needle electrode was inserted into your muscle. This bruising should fade within several days. The neurologist will interpret the results of your exam and prepare a report. Your primary care doctor, or the doctor who ordered the EMG, will discuss the report with you at a follow-up appointment.
An EMG is a very low-risk exam. However, you may feel sore in the area that was tested. The soreness may last for a few days and can be relieved with an over-the-counter pain reliever, such as ibuprofen. In rare cases, you may experience tingling, bruising, and swelling at the needle insertion sites. Make sure to tell your doctor if the swelling or pain becomes worse.
What will my electromyography results tell me?
Your doctor may review the results with you right after the procedure. However, if another healthcare provider ordered the EMG, then you may not know the results until you attend a follow-up appointment with your doctor.
If your EMG shows any electrical activity in a resting muscle, then you may have:
-A muscle disorder
-A disorder affecting the nerves that connect to the muscle
-Inflammation caused by an injury
-If your EMG shows abnormal electrical activity when a muscle contracts, then you may have a herniated disc or a nerve disorder, such as ALS or carpal tunnel syndrome.