Electromyography (EMG) is a diagnostic procedure to examine the electrical activity of muscles that are transmitted by the motor neurons in the muscles. The test helps check the health of the muscles and the motor neurons or the nerves that control the muscles. An EMG is recommended if your muscles indicate any disorder. The symptoms of muscle or nerve disorder of the muscle could be numbness of the muscles, tingling, muscle cramp and weakness and pain in the limbs, paralysis and involuntary twitching of the muscles called tics. Muscle disorders can be due to several reasons like polymyositis or muscular dystrophy, diseases like myasthenia gravis wherein the muscle and nerve connection gets affected, polio or amyotrophic lateral sclerosis (ALS) due to affected motor neurons in the spinal cord or brain, due to affected nerve root causing herniated disk in the spine or due to peripheral neuropathies or carpal tunnel syndrome. There are a few other use of EMG as well like studying kinesiology, guiding botulinum toxin and phenol injections in the muscles, controlling signals for prosthetic limbs and for monitoring neuromuscular function in case of general anaesthesia done by neuromuscular-blocking drugs. Appropriate preparation is important before getting the test done like letting the doctor know about any on-going medication, if you have bleeding disorder or if you have a pacemaker or any other device implanted in the body. Before having EMG you must not smoke for at least three hours, should bathe and clean the body off any oil and dirt and avoid using cream or lotion after having bath and put on comfortable clothing so that there is no obstruction during the procedure.
The first step in conducting the procedure is cleaning the skin where the test will be done. So, first the skin is cleaned by rubbing alcohol with a cotton pad. Thereafter, the procedure is started and done in two parts: first part of the test is known as nerve conduction study and the second part is called needle EMG. Before commencing with the procedure it has to be decided where exactly the needle and electrodes will be placed. The specific muscle selection and size of the muscle are important factors for placing the electrodes. If a person has more body fat, it is difficult to detect EMG signals. The best location for placing the electrodes is on the longitudinal midline near the belly as this part represents both the motor point of the muscle and the insertion point in the tendon part of it. The nerve conduction study is also known as surface EMG as the pair of surface electrodes is placed on the muscle and is used to study only the superficial muscles. The second part of the procedure that involves needle electrodes includes direct insertion of the needle sensors into the muscle tissue. This part examines muscle activity both while contraction and relaxation. The nerve conduction study reveals the communication between the motor neurons and the muscles whereas, needle EMG evaluates the electrical activity of the muscle. During the test procedure, electrical signals emitted are translated to numerical values or graphs on the computer screen, which are then interpreted by the expert.
Person experiencing the symptoms of numbness, tingling, cramps, pain, weakness, paralysis and involuntary twitching of the muscles due to some possible underlying causes like muscular dystrophy, myasthenia gravis, radiculopathies, amyotrophic lateral sclerosis (ALS) and peripheral nerve disorders like carpal tunnel syndrome will be eligible for the treatment. But, if the person has devices like pacemaker or defibrillator implanted in the body, the doctor must be informed about it as EMG cannot give proper signals in their presence.
People who do not experience the symptoms for very long, or do not have any such muscle disorder causing such symptoms are not eligible for the diagnostic test. Also, in case the symptoms are present in the person and require the test evaluating electrical activity of the muscle, but have certain implantable devices pacemaker and defibrillator, then the signals can be erroneous. Hence, in such a case the person may not be eligible for getting the test conducted.
There can be very few side effects or risks associated with EMG test. Some soreness can occur at the site of the test where the needle electrodes were inserted. But the soreness goes away in a few days either on its own or by using pain relievers like ibuprofen. In case, there is swelling, tingling and bruising of the area for more than a few days, it can be conveyed to the doctor to get rid of it.
After the test is done, the test site may show some soreness and the patient may feel tingling, swelling and painful sensation which must be discussed with the doctor for immediate solution. The doctor may also give you some instruction based on the condition, after the test has been performed.
The test procedure takes 30-60 minutes to complete and the after effects of the test like soreness, pain, tingling and swelling of the test site may last only for a few days.
The cost of performing the test anywhere in India ranges from Rs. 500 to Rs. 8,000 depending upon the city, laboratory and to some extent the severity of the disease too.
The results obtained after the test are then studied and evaluated by the physician. Based on the test results the patient will be prescribed with medication if required.
There is no alternative to study muscle function except electromyography.