EMG- Electromyography

What is electromyography?

Electromyography is an electrodiagnostic test. It evaluates the functioning of the muscles and the nerves that control them. Electromyography is used to help detect neuromuscular abnormalities. Put simply, EMG detects the presence, location, and extent of diseases that damage the nerves and muscles.

Nerve conduction studies (NCS) and Electro-encephalography (EEG) are some other commonly performed electrodiagnostic tests. There is an old saying that “Electromyography is an extension of the percussion hammer”.

Why has my doctor ordered electromyography?

Your doctor will ask you to go through an EMG if you suffer from the following signs and symptoms-

– Tingling
– Radiating pain or burning sensation
– Numbness
– Decreased sensation
– Muscle spasms or weakness
– Non-specific limb pain
– Difficulty in performing daily tasks as well as tasks which require fine motor control.

What are the medical conditions that an EMG can diagnose?

Electromyography can detect a plethora of neuromuscular disorders, the prominent ones being:

– Amyotrophic lateral sclerosis
– Carpal tunnel syndrome
– Cervical spondylosis
– Guillain-Barre syndrome
– Lambert-Eaton syndrome
– Muscular dystrophy
– Myasthenia gravis
– Peripheral neuropathy
– Polymyositis

Am I at risk while undergoing EMG?

EMG is a minimally invasive procedure. EMG needles are used for only one patient and are not recycled. Complications though uncommon may involve bruising, bleeding and infection at the puncture site. Nerve injury is another rare complication of this procedure.

Pneumothorax is a rare complication when muscles along the chest wall are examined. (Needle electrodes used to invade the muscles may lead to an air leak in the region between the lungs and chest wall).

How many cases of ALS are reported in India each year?

ALS is counted as a rare disease with only 6 out of 100,000 people diagnosed with this condition every year, worldwide. In India, ALS is reported in 5 people out of every 100,000 people. Contrary to popular belief, only 10% of all cases of ALS are inherited genetically. 90% of all ALS cases are sporadic. It is twice as common in men as compared to women.

What are the precautions that I need to take?

Do I need to fast before my EMG test?

There is no need to fast before an electromyography test. Your physician may advise you to take a light meal on the day of the test. You may also be instructed to abstain from cigarettes and caffeinated beverages (coffee, cola, tea) two to three hours before the test.

Is an EMG test painful?

An EMG employs fine needles that are inserted in your muscles. The needles have microscopic electrodes that pick up electronic signals (both normal and abnormal) from the muscles.

As is evident from the description of the procedure above, mild discomfort and pain may be experienced by you. EMG is a minimally invasive test and no pain medication, sedation or anesthesia is required.

How to prepare for EMG procedure?

– You will be asked to change into a hospital gown. The gown makes it easier for your physician to access different parts of your body.

– A technician will make sure that you are not wearing any jewelry or any metallic object.

– EMG is performed as an outpatient procedure by a neurologist (a doctor who specializes in brain and nerve disorders). No sedation or anesthesia is required.

– Before embarking on the test, the neurologist will explain the procedure of EMG to you.

– He will inform you that you may feel slight pain when needles are inserted in your muscles.

What happens during the EMG procedure?

– You will remain seated on a chair or may be asked to lie down on an examination table.

– The muscle to be studied will be identified and located by the neurologist.

– The skin will be cleaned with an antiseptic solution and a fine, sterile needle inserted into the chosen muscle.

– Each needle has a microscopic electrode that picks up electrical signals given off by a muscle. This is the active electrode. A ground electrode (reference electrode) is placed under your arm or leg.

– The activity of the muscle being examined is measured and displayed on the oscilloscope. An audio amplifier is sometimes used to evaluate the sound of the electric potentials.

– Needles may be inserted up to five times for an elaborate examination.

– During the procedure, the neurologist may ask you to relax and contract your muscles at specific junctures.

-You should inform the neurologist if you experience severe pain or discomfort during the test.

What should I do after the EMG procedure?

You may feel pain and bruise at the sites where the needle electrode punctured your skin. The bruising resolves in a few days. Consult your doctor if it persists. You may also experience muscle soreness for a few hours after the EMG test.

If you experience an increase in pain, swelling or pus at the site of insertion of the needle, consult your physician.

How long does an EMG test last?

An electromyography test lasts from half an hour to two hours. The duration of the test depends on the condition being tested and subsequently, the findings of the test.

Who will interpret the results of my EMG?

A neurologist will interpret the findings of your EMG test. The findings of an EMG test are correlated with the clinical examination before a diagnosis is arrived at.

What is the cost of an EMG test in India?

The cost of getting an EMG done in India ranges from Rs. 2000 to 4000 depending on the regions examined and the extent of the test.

What are the advantages of performing an EMG?

– EMG can distinguish myopathic from neurogenic muscle wasting.

– It can detect abnormalities in clinically normal muscles which may be undergoing chronic denervation.

– It can differentiate focal nerve, plexus, or radicular pathology.

– EMG is an obligatory investigation in motor neuron diseases.

What are the limitations of an EMG test?

– In obese patients and patients belonging to geriatric age group, technical difficulties are encountered.

– EEG test, though minimally invasive can be a source of discomfort to the patient.

– If performed immediately after an injury, the results may not be conclusive. Electromyographic changes due to injury do not appear until 18 to 21 days later.

– An EMG is no substitute for a thorough neurological consultation and subsequent clinical examination. The two should complement each other.

What are the other common electrodiagnostic tests?

Nerve conduction studies (NCS)- Nerves are stimulated electrically with small safe pulses over several points on the skin, usually on the limbs, and the responses obtained are jotted down. This test is done in order to ensure that the nerves, muscles and neuromuscular junctions (the portion responsible for communication between the nerve and muscle) are working optimally and to detect any abnormality if they are not. An EMG is usually performed immediately following a nerve conduction study.

Electroencephalogram (EEG)- An EEG test provides information about the electrical activity of your brain at the time the test is carried out. Electrodes are placed on your scalp during this procedure. EEG test is done to evaluate patients suffering from epilepsy. Other indications include- head injury, encephalitis, brain tumor, stroke, sleep disorders, and encephalopathy.