Nerve Conduction Study: Uses, Procedure and Results

01The test

What a nerve conduction study measures

Nerves control muscles and carry sensation by sending electrical signals. MedlinePlus explains that a nerve conduction study measures how fast and how well these signals move along your nerves, and that a damaged nerve has a slower and weaker signal. The speed of the response is called the conduction velocity.

MedlinePlus’s encyclopedia adds that conduction velocity depends on the diameter of the nerve and on its myelin, the fatty insulating layer around nerve fibers. Normal ranges vary slightly between laboratories and with age: newborns have values about half those of adults, and adult values are reached by about age 3 or 4.

02Reasons

When it is requested: numbness, tingling, weakness

According to MedlinePlus, a doctor may request a nerve conduction study, often with an EMG, if you have symptoms of a nerve or muscle disorder, such as:

• tingling or numbness in the arms, legs, hands, feet or face, such as tingling in the feet or hands that go numb at night
• muscle weakness
• muscle cramps, spasms or twitching
• paralysis of any muscles

The test is used mainly to check for nerve damage and, together with EMG, helps tell whether symptoms come from a nerve or a muscle problem.

03Procedure

How the test is done: surface electrodes and brief pulses

MedlinePlus explains that adhesive patches called surface electrodes are placed on the skin over nerves or muscles at different spots. A very mild electrical pulse is delivered through other patches or a handheld stimulator to stimulate the nerve, and the electrodes record the response. The distance between the electrodes and the time the signal takes to travel are used to calculate its speed.

It is normal for several different nerves to be tested. You will usually sit or lie on a table or bed. MedlinePlus gives a duration of 15 minutes to over an hour, depending on how many nerves and muscles are examined.

04Preparation

Preparation: skin, temperature and implanted devices

MedlinePlus gives these preparation points:

• stay at a normal body temperature: being too cold alters nerve conduction and can give false results
• do not wear lotions, sunscreen, perfume or moisturizer on the day of the test
• wear loose, comfortable clothing that gives easy access to the area being tested
• tell the team if you have a pacemaker, cardiac defibrillator or another implanted device such as a deep brain stimulator, as special steps may be needed
• tell them if you take blood-thinning medicines, especially if a needle EMG will also be done

Being warm simply means arriving at a normal body temperature, not heating the skin. Do not stop any medicine on your own: ask the doctor who prescribes it or the testing team.

05Comfort

What you feel during the test

MedlinePlus explains that the pulse may feel like an electric shock or a mild tingling, like static electricity, and that discomfort depends on how strong the pulse is. You should feel no pain once the test is finished.

Experiences vary, so it is not accurate to promise that the test is painless for everyone. If a pulse feels too uncomfortable, say so: the team can explain each step as the test goes on.

06EMG

How it differs from and complements needle EMG

A nerve conduction study uses only surface electrodes on the skin and measures how signals travel along nerves. A needle EMG, by contrast, records electrical activity from a fine needle electrode placed in a muscle while it is at rest and while you tighten it. MedlinePlus explains that the two tests can be done separately but are usually done at the same visit, with the nerve conduction study done first.

Together, they help doctors locate the problem: in the nerve, the nerve root, the connection between nerve and muscle or the muscle itself. After a needle EMG, muscles may be sore and slightly bruised for a few days; after a nerve conduction study alone, MedlinePlus notes there should be no pain once it is finished.

07Results

What results can show

MedlinePlus explains that abnormal results most often reflect nerve damage, which may affect the long part of the nerve cell (axon), block the signal somewhere along the nerve, or damage the myelin insulation. Many conditions can cause this, including:

• nerve compression such as carpal tunnel syndrome, tarsal tunnel syndrome or ulnar nerve dysfunction
• peripheral neuropathies, for example related to diabetes, alcohol or kidney failure
• Guillain-Barré syndrome and chronic inflammatory polyneuropathy
• injuries to nerves or to the brachial plexus
• inherited conditions such as Charcot-Marie-Tooth disease
• nerve root compression from a herniated disk

MedlinePlus stresses that, to understand the results, your doctor will consider your symptoms, medical history and other tests. An abnormal result does not by itself name one specific disease.

08Limits

Why a normal result does not rule out every nerve problem

MedlinePlus explains that a nerve conduction study shows the condition of the best surviving nerve fibers. As a result, in some cases the results may be normal even when there is nerve damage.

A normal result is useful information, but it does not close the question on its own. If symptoms continue or change, your doctor may consider them together with the examination, a needle EMG, blood tests or imaging, as they consider appropriate.

09Sources

Where the sources differ

The two MedlinePlus pages, the lab test guide (April 2024) and the medical encyclopedia (April 2025), agree on the procedure and the purpose of the test. The lab test guide focuses on symptoms, the order of the tests and duration; the encyclopedia adds the importance of body temperature, implanted devices such as deep brain stimulators, a longer list of conditions and the key limit that results can be normal despite nerve damage. Normal ranges vary between laboratories, so they are not listed here.

If your doctor has asked for a nerve conduction study or EMG, our clinical neurophysiology service in Bilbao performs these tests and explains which nerves will be studied and why (consultations are in Spanish). Diagnosis and treatment remain with your referring doctor, and the test does not replace a medical assessment.

10Summary

In summary

A nerve conduction study uses skin electrodes and mild electrical pulses to measure how fast and how strongly signals travel along nerves. It is requested for numbness, tingling, weakness or cramps and is often combined with a needle EMG. Arrive warm, without creams, and tell the team about implanted devices and blood thinners. The pulses may feel like brief shocks or tingling.

Results are interpreted together with your symptoms and other tests: an abnormal result does not equal a single disease, and a normal one does not rule out every nerve problem. It helps to bring written questions to the appointment: which nerves will be tested, what question the test should answer and how you will receive the results.