Nerve Conduction Study

What is a nerve conduction study?

A nerve conduction study (NCS) is a diagnostic test that evaluates the function of your peripheral nerves. An NCS can help detect the presence and extent of peripheral nerve damage. Your peripheral nerves are the nerves that lie outside of your brain and spinal cord (central nervous system).

More specifically, an NCS measures the flow of electrical current through:

• Motor nerves: Nerves that control your muscles and movement.
• Sensory nerves: Nerves that carry signals to your brain about things you touch, taste, smell and see.

Your healthcare provider may recommend an NCS if you have symptoms such as tingling or numbness in your arms, legs, hands, feet and/or face. You may have the study in an outpatient setting or as part of your stay in a hospital, depending on the situation. Providers usually perform an NCS alongside an EMG (electromyography) test.

What does a nerve conduction study diagnose?

Nerve conduction studies help diagnose issues with your peripheral nerves — mainly peripheral neuropathy and nerve compression syndromes. They can help healthcare providers determine the cause, severity and prognosis of these conditions.

Peripheral neuropathy

Peripheral neuropathy happens when your peripheral nerves are damaged. Many different conditions can cause peripheral neuropathy. It can affect different parts of your body, depending on how and why it happens.

Some common causes of peripheral neuropathy include:

• Diabetes.
• Vitamin deficiencies.
• Thyroid.
• Alcohol use disorder.
• Certain autoimmune conditions, like lupus, rheumatoid arthritis, Sjögren syndrome, vasculitis and Guillain-Barré syndrome.
• Infections from viruses, such as HIV, or bacteria (such as Borrelia burgdorferi, which cause Lyme disease).
• Medications, such as chemotherapy.
• Direct injury to your nerves from trauma or surgery.

Nerve compression syndromes

A nerve compression syndrome can occur when there’s pressure on a peripheral nerve. It can lead to peripheral neuropathy.

Examples of nerve compression syndromes include:

• Carpal tunnel syndrome.
• Sciatica.
• Radial tunnel syndrome.
• Thoracic outlet syndrome.
• Meralgia paresthetica.

What’s the difference between a nerve conduction study and an EMG?

Neurologists often perform an EMG (electromyography) test and a nerve conduction study in the same setting, but they’re different tests. An EMG measures how much electrical activity a muscle contraction produces. An NCS assesses the flow of electrical current through a peripheral nerve before it reaches a muscle. It can also detect the flow of electricity through sensory nerves.

When providers perform these tests together, it helps them see if your symptoms are the result of a muscle disorder or a nerve issue.

How does a nerve conduction study work?

Nerves are like cables that carry electrical impulses or signals between your brain and the rest of your body. These impulses help you feel sensations and move your muscles. A nerve conduction study works by testing the transmission of these signals, especially the speed at which they travel and their “strength.”

The study involves wires (electrodes) taped to your skin in specific places along a nerve pathway. A provider stimulates the nerve with a mild electrical shock. As the electrical current travels down the nerve, the electrodes record the current and how fast it’s traveling. If the provider stimulates a motor nerve, they measure the response of the muscle it controls. If they stimulate a sensory nerve, they record the response somewhere else along the nerve.

In healthy nerves, electrical signals can travel up to 120 miles per hour. If your nerve is damaged, the current will be slower and weaker. By stimulating the nerve at various places, the provider can determine the specific site of the nerve injury or issue.

How do I prepare for a nerve conduction study?

Before you have a nerve conduction study, you should:

• Bathe or shower and wear comfortable, loose-fitting clothing.
• Avoid putting cream, lotion or perfume on your skin. Creams and lotions can affect the test’s accuracy.
• Tell the provider performing the study if you have a pacemaker or any other electrical medical device.

What should I expect during a nerve conduction study?

The process can vary for a nerve conduction study, depending on the reason for the test and which nerves the provider is assessing. But in general, you can expect the following during a nerve conduction study:

• You’ll sit or lie down for the test.
• A healthcare provider will stick electrodes to the surface of your skin above the nerves they’re assessing.
• They’ll attach different types of electrodes to the muscle or skin area that those nerves control.
• The provider will then deliver a small electrical impulse to your nerves to send a signal to the muscle it controls. You may feel a mild tingling feeling.
• They’ll record the time it takes for your muscle or skin to respond to the nerve signal.
• Then, they’ll repeat the same process in the next nerve until they’ve gathered enough information.

Providers usually perform an EMG test after the nerve conduction study.

How painful is a nerve conduction study?

Although the electrical stimulation may startle you initially, it shouldn’t be painful. The shock feels similar to a shock you experience from static electricity, or it may feel like a mild tingling. Most people can complete the test without issues.

How long does a nerve conduction study take?

A nerve conduction study can take anywhere from 15 minutes to an hour or more. It depends on how many nerves your healthcare provider tests.

What are the risks of a nerve conduction study?

Nerve conduction studies are generally safe. While the electrical pulses may be uncomfortable, the sensation is brief and shouldn’t be painful.

What do the results of a nerve conduction study mean?

Although nerve conduction studies can be very helpful, they alone don’t usually provide a diagnosis. Your healthcare team providers will assess the results along with other medical tests, your medical history and symptoms to determine a diagnosis.

When should I know the results of the test?

You can expect to receive the test results typically within 24 to 48 hours after testing.

A note from Cleveland Clinic

If you have signs of nerve damage or injury, a nerve conduction study can help your healthcare provider learn more about what’s going on. It also helps them plan your treatment. If you have any questions about the test, don’t hesitate to ask them. Your provider is available to help and support you.