NCV & EMG

EVERYTHING YOU MAY WANT TO KNOW

Nerve conduction studies and needle electromyography colloquially are referred to as NCV/EMG, which is an electrical study of the peripheral nervous system and muscles. These electrodiagnostic elective testing procedures aid in the determination for evidence of neurogenic or myopathic disease contributing to the patient's symptoms.

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Consider MRI or X-ray which are diagnostic sophisticated photographs, unlike these imaging measures the EMG and NCV provide information in real-time about what is occurring physiologically with respect to the nerve and the muscle.

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Easy EMG: Lynn Weiss MD, Julie Silver MD, and Jay Weiss MD. 2004, Elsevier Inc.

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There exist more than 200 types of peripheral neuropathies, having top-of-the-line diagnostic tools aids in proper diagnosis. This is where NCV/EMG play a vital role in the identification of type, location and the temporal degree of peripheral neuropathies, and aid to properly diagnose these diseases.

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The EMG test helps to clarify the cause of symptoms by confirming any nerve or muscle damage. This is especially helpful when exam findings or other diagnostic tests are not clear, inconclusive, or the ordering physician desires more levels of evidence. Electrodiagnostic testing cannot tell you the cause of nerve or muscle damage, it only confirms details of the damage.

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THE FUNCTION OF YOUR PERIPHERAL NERVOUS SYSTEM

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The nervous system includes the brain, the spinal cord, and all the connections from the spinal cord to the muscles (or organs)-functioning as an electric circuit. When you desire to execute an action like scratching an itch, the initiation of these actions produces an electric signal which travels down the spinal cord and out of the spinal column which terminates on the desired muscle/organ to execute the action.

More so, your nervous system is responsible for your sensory abilities. The reason you feel a cool breeze, see light, smell flowers are dependent on the proper functioning of your nervous system.

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It's very important we have the ability to evaluate the peripheral nerves and spinal cord when evaluating spinal problems or other musculoskeletal issues. Specialized nerve tests called Electromyography and Nerve Conduction Studies are designed to diagnose abnormalities in the functioning of nerves.

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WHY DO I NEED AN EMG? WHAT IS AN EMG TEST USED TO DIAGNOSE?

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Maybe you've been in a car accident, a slip-and-fall at work, sports injury or the aging process is getting the best of you. It's likely you feel weakness, numbness and/or tingling, as one of many examples of symptoms. Are these symptoms a result from a brain injury or spinal cord lesion? Perhaps it involves a peripheral nerve entrapment or the muscle in your leg? An EMG can provide clarity in these questions.

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Conditions NCV/EMG Commonly Aids to Diagnose

• Cervical/Lumbar radiculopathies (commonly seen in MVA/Work Comp patients)

• Carpal/Tarsal tunnel syndrome

• Cubital tunnel syndrome

• Myopathy/myositis

• Chronic inflammatory demyelinating polyradiculoneuropathies

• Guillain-Barre syndrome

• Myasthenia gravis

• Lou Gehrig's Disease/Amyotrophic lateral sclerosis (ALS)

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THERE ARE TWO COMPONETS TO AN NCV/EMG STUDY

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1. Nerve conduction studies (NCS/NCV): studies of the physiological function of peripheral nerves—primarily of the arms and legs.

2. Needle electromyography (EMG): which directly tests the muscle and indirectly test the peripheral nerve function via the introduction of a very small gauge needle into the muscle belly; EMG aids in the direct waveform identification of neuropathic and muscle disease.

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NERVE CONDUCTION STUDIES

These tell us about the health of the nerves in the extremities. We mimic the "electrical signal" from your spinal cord with a small stimulus at one part of the nerve and record that impulse at another part of the nerve or at a muscle supplied by that nerve. This part tells us if the individual nerve is conducting that electric signal properly. This produces a slight sensation that travels down the arm or leg.

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EMG IS DIFFERENT FROM NCV:

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• During an EMG, a needle is inserted into the muscle rather than electrodes that are placed on the skin during the NCV.

• There is no stimulus in EMG; rather you are looking at the intrinsic electrical activity of the muscle.

• You get direct information about the muscles in EMG and indirect information about the nerves that supply those muscles.

Easy EMG: Lynn Weiss MD, Julie Silver MD, and Jay Weiss MD. 2004, Elsevier Inc.

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WHEN TO CONSIDER ASKING YOUR PHYSICIAN FOR EMG?

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If you have one or more of the following symptoms:

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• Numbness

• Tingling (paresthesia)

• Burning

• Pain

• Weakness

• Weakness/Limp

• Muscle atrophy (loss)

• Decreased tendon reflexes

• Fatigue

Easy EMG: Lynn Weiss MD, Julie Silver MD, and Jay Weiss MD. 2004, Elsevier Inc.

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HOW LONG DOES AN EMG TAKE?

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An EMG can last anywhere from 30-60 minutes, depending on what questions we are trying to answer. Based on what we are finding, sometimes we may have to add a couple extra nerves or muscles, which may make the test last longer.

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WHAT ARE THE LIMITATIONS/RISKS OF AN EMG?

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What an EMG cannot tell us is whether the problem is in the brain or the spinal cord itself. We rely on imaging and other diagnostic tests of the brain and the spinal cord to show us problems there. The risks of an EMG are minimal. The needles are so small that permanent neurologic injury by nicking a nerve is very unlikely. What we see most often is that the muscles we sampled with the needle tend to be sore for hours or a day before returning to normal. But the information we gain from doing the test can help determine the best treatment path for you.