An EMG test is performed by a neurologist who frequently has had further training in the subspecialty of clinical neurophysiology.
Why is an Electromyography Required?
Nerves send out electrical signals to make your muscles react in certain ways. As your muscles react, they give off these signals, which can then be measured.
In some medical conditions, the electrical activity of the muscles or nerves is not normal. Finding and describing these electrical properties in the muscle or nerve may help your doctor diagnose your condition.
At the EMG clinic, we can perform two types of tests:
- Nerve Conduction Study
- Needle EMG
Electromyography (EMG) is often performed simultaneously with nerve conduction studies, which aid in diagnosing peripheral nerve disorders. EMGs are most often done for the following reasons:
- To diagnose the source of pain, numbness, tingling, weakness or cramping in the muscles
- To differentiate between true muscle weakness and limitations due to pain
- To determine if muscles are working properly
- To differentiate between muscular conditions and dysfunction due to nerve disorders
Both NCS and EMG testing can be performed multiple times throughout investigation or treatment and allows for real-time evaluation of a patient peripheral nervous system.
EMG tests allow for rapid, tailored treatment decisions in the event of ongoing nerve and muscle injuries (acute denervation), versus more conservative treatment plans for patients with chronic injuries (chronic denervation)
In the event of neuromuscular injury, the electrical activity recorded from affected muscles will be different compared to a healthy muscle. This allows for precision when identifying the specific location/level of the neuromuscular injury.
What Can an EMG Diagnose?
EMGs may aid with the diagnosis of
- nerve compression or injury (such as carpal tunnel syndrome),
- nerve root injury (such as radiculopathy, ie, a pinched nerve in the neck or lower back, diabetes & other peripheral neuropathies),
- other problems of the muscles or nerves.
Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.
In the event of severe peripheral nerve injury, for example, sometimes muscles can become weaker than their healthy counterparts; EMG helps to evaluate the severity of muscle denervation (where the nerve no longer gives power to its respective muscles) and determine whether there is ongoing nerve dysfunction (acute) or the injury is chronic.
If there is damage to the nerve supplying the muscle, the doctor can see it. The test allows the doctor to identify the nerve in your back causing the problem or the nerve in an arm or leg (such as the arm in carpal tunnel syndrome).
Before an Electromyography
In preparing for an ElectromyographyYou will be given instructions on how to prepare for the test.
- Take a bath or shower to remove all oil from your skin before your test,
- Do not use body lotion, creams, powders, or emollients on your hands and feet (the most common sites of your nerve tests) on the day of the test,
- On the day of the appointment, bring a list of any medications you are taking and all insurance cards so we can make copies.
- Advise the neurologist performing the test if you:
- Use a pacemaker or other similar devices
- Take aspirin, blood thinners (like Warfarin Plavix, Heparin)
- Have haemophilia.
- If you have myasthenia gravis, please call your primary care physician 24-48 hours before your appointment and ask if you should take any medications before your EMG test.
If you have a needle EMG test, you should advise your GP and the neurologist. A measurement of how thin your blood is may be important before that test can be performed.
During an Electromyography
Firstly you will be asked to position yourself comfortably
- Your target skin area will be prepared
- Small pins or needles are inserted into muscles to measure electrical activity. The needles are different from needles used for the injection of medications. They are small and solid, not hollow like hypodermic needles. Because no medication is injected, discomfort is much less than with shots.
- Small electrodes (metallic patches that can conduct signals) are placed on your skin
- A machine is used to stimulate the nerves.:
- Records each stimulation
- Records how long the signal travels along the nerve.
- Measures the results
- Creates graphs, sounds or numbers
- Your doctor how well the nerves work.
Some patients are understandably anxious about the intensities of the small safe electrical pulses passed via the skin but usually relax quickly when they know what to expect.
Often muscle activity is monitored through a speaker during the test, which may make a popping or soft roaring noise.
Each electrical charge feels like a small static electricity shock. Some people describe the feeling as a “strong tap.”
You must remain relaxed for the recordings to minimise the ‘noise’ (interference) in the recordings from excessive muscular activity.
Electromyography (EMG) testing involves the use of small electrode needles placed into the muscle of the patient, which allows for the recording of a muscle’s electrical activity.
People usually have a small amount of discomfort during EMG testing because of pin insertion. Disposable needles are used so there is no risk of infection.
During a Needle Electromyography (EMG)
A Needle Electromyography (EMG) involves the same process as a Surface Nerve Conduction Study except for the method of positioning the electrode.
During the procedure, a small needle is inserted through the skin into a muscle belly. Sterilisation of the skin and a local anaesthetic are not generally required. Usually, the consultation and procedure take about 30-45 minutes. More complicated assessments may demand more time.
Needle EMG may produce some minor bruising on the skin and muscle. With any procedure such as this, there is a small risk of infection.
