Following your consultation at LBSM, you may have been referred for a Nerve Conduction and EMG Study.
This guide takes you through the relevant information about what to expect during this process. Please take the time to read it carefully.
After you have had your investigation, you will have the opportunity to go through the results in detail with the clinical team and work out the next steps together.
Please feel free to contact us if you have any queries about anything to do with the process of getting your scan.
- What is a Nerve Conduction and EMG Study?
- What does EMG stand for?
- How do EMG/Nerve Conduction studies work?
- Is having a Nerve Conduction/EMG Study safe?
- How will the test help me?
- Is there anything I need to do before the test?
- What happens on the day of the test?
- What happens during the test?
- What happens after the test?
What is a Nerve Conduction and EMG Study?
This is a routine test performed in specialist hospitals. The Nerve Conduction test measures the speed at which impulses travel along a nerve. The EMG (electromyography) records the electrical impulses that your muscles produce. These tests help us to work out how well your nerves and muscles are functioning. They are often referred to collectively as an EMG test and may incorporate one or both of the above techniques.
What does EMG stand for?
Electro- The electrical impulses that are being measured.
Graphy- The way the results of the test are presented.
How do Nerve Conduction/EMG studies work?
The Nerve Conduction Study records how fast nerves send messages to the brain and back. In the test, we stimulate the nerves using electrodes placed on the surface of a person’s skin. We can then record how fast the impulse travels to another point, where it is recorded using a surface electrode placed on the skin (on rare occasions a fine needle electrode in the muscle may have to be used to take a recording). This tells us how fast the nerve is working.
EMG studies the electrical activity of the muscles. This is usually recorded using a small needle electrode inserted through the skin into the muscle, which produces a short pinprick sensation. Once in place the activity in the muscle can be observed at rest and then whilst being used.
Is having a Nerve Conduction/EMG Study safe?
During the nerve conduction test we stimulate the nerve and this results in you feeling a tapping/tingling sensation. Most people do not find this too uncomfortable. If you have a cardiac pacemaker implanted, then please tell the technician and the doctor before you have the test, you can still have the test but we need to modify the position of the electrodes slightly. If you are taking anticoagulant (blood thinning) treatment, for example, Warfarin tablets, please tell us when you ring to make your appointment. You can still have the nerve conduction part of the test but we may not perform the EMG.
How will the test help me?
The measurements and observations that we take from these tests help us to find out whether the problems you are having are caused by trapped or damaged nerves in your arms, legs, neck, back or face. We also use the tests to investigate a wide range of nerve and muscle disorders. The results from the tests help your consultant to make a diagnosis and to provide the right treatment for you.
Is there anything I need to do before the test?
Before you have the test, you should:
- Remove any jewellery, as this will make it easier for us to attach the electrodes. Leaving your jewellery at home is also a better way of keeping it safe.
- Wear clothing with short sleeves and/or loose clothing e.g. loose trousers or a skirt, as this will make it easier if we need to look at your legs or arms.
- Avoid using lotions and creams before your test as cream or lotion on your skin can make it difficult for us to attach the electrodes.
- Eat and take any medication as normal. It is helpful if you bring a list of your current medications with you.
What happens on the day of the test?
Our Nerve Conduction and EMG studies are performed by neurologists or neurophysiologists. They are highly qualified doctors and healthcare professionals who specialise in disorders of the nervous system. They may ask you some specific questions around your symptoms and further details.
You will be taken into a testing room where the study will be performed and will be made comfortable on the couch. If your hands and/or feet are cold then we will put them in warm water to warm them up, this is because if your skin is cool it can affect the results. During this time you will be able to ask any questions you have and the technician will be happy to help where they can or they will ask the doctor to answer your queries.
What happens during the test?
There are 3 parts to the test and these are described below. You may not need all three, this depends on your clinical problem and the doctor’s findings during the test.
Part 1. Sensory nerve testing
During this test you need to stay as still and relaxed as possible. First, we clean your skin with an alcohol wipe. This improves contact between your skin and the electrode giving much better results. Then the nerves, which supply sensation are tested using ring electrodes on the fingers or button electrodes on all other parts of the body. For a short time during the test you will feel a repetitive tapping/tingling sensation. We will also need to make some measurements between the electrodes using a tape measure and a marker pen. This does mean that some small dots are made on your skin but these will wash off. The test checks your sensory nerves for any delays in sending messages along your limbs.
Part 2. Motor nerve testing
This test also allows us to check the nerve supply to your muscles. You will feel a tapping/tingling sensation similar to that felt during part 1, this time it is caused by a muscle being stimulated. You will also see that the muscle being tested twitches. Again we will mark points and take measurements. Any delays in the stimulus being transmitted can give valuable information to the doctor about the nerve supply.
Part 3. EMG Testing
If we need to look at your EMG signals, we will insert a small needle into the muscles to be tested. The needle we use is for single use and is disposed of after each patient. It is specifically designed to carry a fine recording wire. The Doctor will examine any electrical activity whilst the muscle is at rest. During the next part we will ask you to use the muscles so that we can observe their pattern of activity. The activity is displayed on a screen and 6 can also be heard on a speaker as a crackling sound. We may repeat the test for different muscles. This activity helps the doctor to decide whether the problem is a disorder affecting the nerve supply to the muscle or a disorder of the muscle itself. This is very important when making a diagnosis.
What happens after the test?
The neurologist/neurophysiologist will most likely be able to talk you through their findings as they are carrying out the investigation. The results of the study will then be sent back to your LBSM doctor and they will be able to interpret the findings with you in context of your clinical picture and presentation. After your investigation you should contact the LBSM team to make a follow-up appointment.
Please feel free to contact us if you have any queries about the process of getting your investigation, or the study itself. Look forward to seeing you at your next appointment.
The information in this article has been cited from www.nhs.uk to align with best clinical practice standards.