NERVE CONDUCTION STUDIES AND ELECTROMYOGRAPHY (EMG)

Nerve conduction studies (NCS) and Electromyography (EMG) are used to study the function of nerves and muscles in the body. They are the most useful test for examining these two tissues, as MRI scans and other forms of testing are most often not helpful.

 

Nerves carry electricity in order to relay messages from skin and organs to the brain, but also in order to instruct muscles and organs how to act.

 

How can I prepare for the NCS and EMG study?

 

  • You may need to put on a hospital gown for the test, depending upon what is to be studied.  Try to wear loose clothing that is easy to roll up over arms and legs or to remove. Try not to wear pantyhose, long underwear, or pants that cannot roll up at all.

  • It is important to be clean on the day of your appointment - dirt, grime and oil lead to problems with testing. Try to avoid wearing any skin lotions or moisturizing creams that are not medically necessary - these will interfere with the test and need to be rubbed off before testing.

  • We would ask that you remove all jewellery prior to the testing. If you have a MedicAlert bracelet, please keep this on.

  • Try to bring a list of all current medications and dosages.

  • In rare cases, you may be asked to avoid taking your medication before testing - your doctor will tell you if this is the case.

  • Should you have any chronic infections such as Hepatitis B or C,  HIV or others, please tell us so proper precautions can be ensured.

  • If you are taking any blood-thinners such as coumadin or warfarin or other medicines used to protect against clots and stokres, please let us know.

 

How long will the NCS and EMG study require?

 

  • Depending on the nature of your problem, testing may take anywhere from 30 minutes to 3 hours to complete. Please ensure that you use the washroom before testing commences.

 

NCS rely upon this ability of nerves to transmit electrical conduction. During NCS, we provide small shocks over nerves in order to assess how they are sending a signal.

 

What happens during the NCS and EMG study?

 

NCS testing is performed by medical specialists such as Neurologists and Physiatrists. In order to perform these tests, many months of training and certification are required.

 

NCS are most useful for examining for conditions such as:

 

  • Carpal tunnel syndrome at the wrist

  • Cubital tunnel syndrome at the elbow (funny bone area)

  • Forms of peripheral neuropathy, a widespread form of nerve disease

  • Guillain-Barré syndrome, a form of peripheral neuropathy with rapid onset and great disability

  • Peroneal neuropathy at the knee

  • Spinal disc herniation with spinal nerve root problems (radiculopathies)

 

and many other conditions.

 

 

 

 

Stickers, or electrodes, are placed over the skin to receive signals for nerve conduction studies. In this case, the median nerve is being tested across the wrist for a motor study in which the thumb will twitch upon stimulation.

For motor studies, multiple locations are often tested to determine how the nerve is doing at multiple regions of the nerve. Some nerves are liable to be compressed at certain locations, so it is important to study the areas around this location. In the case above, the median nerve will be stimulated at each of three locations, with the results shown on the screen on the right. These results are analyzed to determine speed and size of the responses.

Before testing, we will make some measurements using a measuring tape. There may be small pen marks used as indicators on your skin. The skin will be cleaned with alcohol. It is important to try to avoid placing creamy solutions on the skin before coming, as this disrupts the signals. Stickers will be placed on the skin over nerves or muscles to receive the signals after stimulation (see above left).

 

A stimulator will be placed on nerves with stimulation starting small and gradually getting bigger until the right amount of stimulation is applied (see above right). These shocks are very brief, far less than a second, and can never be harmful. Although some people find these uncomfortable, most patients find these to be well tolerated.

 

Are there any risks with the NCS and EMG study?

 

Not really - there can be discomfort for some patients. If you are on a blood thinner, then some of the needle pokes may have minor bleeding or a chance to form a bruise. If you have a pacemaker, then we would not shock over that area, and shocks placed elsewhere never affect the pacemaker itself. Needles used are always sterile and never re-used, so there is no risk of obtaining any infection. Sometimes, patients can have discomfort after the needle tests lasting up to a few hours afterwards. There are no other side effects of the testing. You can always drive, walk and perform any task after this is done.

 

What are the tests done during the NCS study?

 

The tests performed can be divised as follows:

 

  • Sensory NCS are performed by electrical stimulation of a peripheral nerve and recording from a purely sensory portion of the nerve, such as on a finger. These shocks are small, and may be felt like a rubber band stretched and hitting against the skin. You will also feel an electrical sensation travelling down the nerve usually. We measure the distance travelled with a measuring tape. On the computer screen (see above), you will see waveforms showing up that allow us to measure the speed and size of the responses. 

  • Motor NCS are performed by electrical stimulation of a peripheral nerve and recording from a muscle supplied by this nerve. These shocks are larger than with sensory testing. You will also feel an electrical sensation travelling down the nerve usually, but you will also notice your muscles contracting, leading to movement that you will not be controlling. We measure the distance travelled with a measuring tape. On the computer screen (see above), you will see waveforms showing up that allow us to measure the speed and size of the responses given at multiple sites along the same nerve.

  • F-wave studies is not really a reflex, per se. It is a signal that started in the nerve and travelled back to the spinal cord, and then came back again to the muscle supplied by the nerve. This allows us to measure the nerve signals at the more proximal parts of the nerves and within the neck or back where spinal nerves exist. You will feel these shocks the same as with the motor NCS studies performed.

  • H-reflex studies are more like a reflex. This study uses shocks over a nerve that travel up to the spinal cord before returning to the muscle supplied by the nerve. This allows us again to measure the nerve signals at the more proximal parts of the nerves and within the neck or back where spinal nerves exist. You will feel these shocks as generally smaller than the motor NCS studies performed.

 

Is this test done for myasthenia gravis?

 

Yes, although differently. In myasthenia gravis (MG), muscle fibers become easily fatigued. When given multiple stimulations, muscles in MG do not respond as well as normal muscles. Thus, we will test using short sequences of rapid, regular electrical impulses, sometimes before and after exercising the motor unit. This will permit the fatiguability of the muscle to be measured. This is called a repetitive nerve stimulation test. In this test, we look for a finding called a repetitive decrement, indicating a neuromuscular junction problem that can occur in myasthenia gravis and related conditions.

What are the tests done during the EMG study?

 

EMG may or may not need to be performed. In most cases, both NCS and EMG are performed together. However, in some cases, only EMG may be required. In other cases, only NCS will be required. This depends upon the nature of the condition being examined.

 

EMG is a technique for evaluating and recording the electrical activity within skeletal muscles. EMG detects the electrical signals within muscle when electrical or voluntary activation occurs. Then, the electrical signals can be analyzed to detect abnormalities where the muscle fibers are acting on their own, the level of muscle activation and recruitment when all muscle fibers are acting together, and to see how the electrical appearances of the  order or to analyze the biomechanics of human or animal movement.

 

The needle used in EMG is very small and thin. Some patients do not even feel the pokes. There can be some discomfort for some patients. If this is ever intolerable, the test would be discontinued. 

 

What is EMG most useful for?

 

  • Some forms of nerve entrapment

  • In some forms of peripheral neuropathy

  • Spinal disc herniation with spinal nerve root problems (radiculopathies)

  • Muscle diseases

  • Motor neuron diseases

 

What happens during the EMG study?

 

The skin is cleaned with alcohol and a sticker is placed on the skin. The small EMG needle is attached to the computer and enters the skin and then the muscle to study the muscle's electricity. This will generally feel like a small poke, like with a mosquito bite. 

 

Then, the needle is moved through the muscle to examine different muscle portions while the muscle is at rest. You may hear noise coming from the computer indicating muscle firing. After this, the muscle will be activated by you moving a part of your body. This will lead to the muscle activity being detected, sounding like a motorcycle or an engine. We will ask you to move the muscle a little bit, then more, then fully to study how the muscle fibers are firing.

 

In some cases, only a few muscles need to be tested. In other cases, a large number of muscles throughout the body will need to be tested.

Burnaby Neurology

FAX (778) 654-7810
CALL (778) 737-6378 (7787DR-NERV)
Email the webmaster at: drcorytothoffice@gmail.com
  • w-facebook
  • Google+ Clean

Clinic Times are generally as follows:

Monday -  Friday     8:00 am - 6:00 pm

© 2015 Cory Toth Professional Corporation

Proudly created with Wix.com

This site was designed with the
.com
website builder. Create your website today.
Start Now