EMG and Nerve Conduction Studies: What to Expect at Your Test

If you have been dealing with numbness, tingling, burning pain or weakness in your arms or legs, your doctor may recommend an EMG and nerve conduction study. Together, these two tests show how well your nerves carry electrical signals and how your muscles respond to them. They are among the most useful tools a neurologist has for finding out where a nerve problem is located, what kind of problem it is and how severe it has become.

Electrodiagnostic testing is performed in our Westwood, New Jersey office. This guide explains what each part of the test measures, who usually needs it, how to prepare and what the experience is actually like, so you can walk in knowing what to expect.

What Is an EMG and Nerve Conduction Study?

The term "EMG" is often used for the whole visit, but the evaluation normally has two parts that complement each other.

Nerve conduction study (NCS)

A nerve conduction study measures how fast and how strongly an electrical signal travels along a nerve. Small sticky electrodes are placed on the skin over a nerve or muscle. A brief, mild electrical pulse is delivered at another point along the nerve, and the electrodes record the response. The computer measures the speed of the signal (conduction velocity), the time it takes to arrive (latency) and the size of the response (amplitude).

These numbers help separate two broad patterns of nerve injury: damage to the insulating myelin coating, which slows the signal, and damage to the nerve fiber itself (the axon), which makes the response smaller.

Electromyography (EMG)

The needle EMG looks at the muscles. A very thin, sterile, single-use needle electrode is placed into selected muscles to record their electrical activity, first while the muscle is relaxed and then while you gently tighten it. Healthy muscle is electrically quiet at rest. Abnormal signals can show that a muscle has lost part of its nerve supply or that the muscle tissue itself is diseased.

Why Your Doctor May Order an EMG/NCS

Electrodiagnostic testing is usually recommended when symptoms suggest a problem in the peripheral nerves, the nerve roots that leave the spine, the junction between nerve and muscle, or the muscles. Common reasons include:

• Carpal tunnel syndrome – numbness and tingling in the thumb, index and middle fingers, often worse at night.
• Ulnar neuropathy – tingling in the ring and little fingers, often related to pressure at the elbow.
• Peripheral neuropathy – burning, numbness or pins-and-needles that usually starts in the feet. Read more in our guide to peripheral neuropathy symptoms and causes.
• Pinched nerve (radiculopathy) – neck or back pain that travels down an arm or leg with numbness or weakness.
• Unexplained muscle weakness, cramps or twitching, which can point to a muscle disease or, less often, a motor neuron disorder.
• Nerve injury after trauma or surgery, to judge how much damage occurred and whether the nerve is recovering.

The test does not just confirm that "something is wrong." It helps distinguish conditions that can feel similar, such as carpal tunnel syndrome versus a pinched nerve in the neck, which often leads to very different treatment.

How to Prepare for Your Test

Preparation is simple, but a few details make the results more accurate:

• Shower on the day of the test and do not apply lotion, cream or oil to your arms or legs. Skin products can interfere with the electrodes.
• Wear loose, comfortable clothing that can be rolled up above the elbow or knee, or be ready to change into a gown.
• Tell us if you take blood thinners such as warfarin, apixaban or rivaroxaban, or if you have a bleeding disorder. Do not stop any medication unless your doctor tells you to.
• Tell us if you have a pacemaker, defibrillator or other implanted device, or if you have lymphedema in a limb.
• Keep your hands and feet warm. Cold limbs slow nerve signals and can make results look falsely abnormal, so we may warm them before testing.
• Eat normally and take your usual medications unless instructed otherwise. No fasting is needed.

Bring a list of your medications and any previous test reports, such as an earlier EMG, MRI or blood work. These help your neurologist decide which nerves and muscles to examine.

What the Test Feels Like

Many people worry that the test will be painful. Most patients find it very tolerable, and it helps to know what is coming.

During the nerve conduction study, each electrical pulse feels like a quick tap or a brief static shock, and it may make the muscle twitch for a moment. The sensation stops as soon as the pulse ends. Several pulses are usually given for each nerve.

During the needle EMG, you will feel a small pinch as the fine needle goes in, similar to a quick injection, but nothing is injected. You may feel a dull ache while you tighten the muscle. The needle is moved only slightly, and the neurologist examines only the muscles needed to answer your clinical question.

A complete study usually takes between 30 and 90 minutes, depending on how many limbs and nerves need to be tested. You can drive yourself home and return to normal activities right away. Some people notice mild soreness or a small bruise where the needle was placed, which fades within a day or two.

Understanding Your Results

Unlike a blood test that simply comes back "high" or "low," an EMG/NCS is interpreted in real time by the physician performing it, who adjusts the examination as the findings unfold. Your neurologist combines the numbers with your symptoms and physical examination to answer questions such as:

• Is there a problem with the nerves, the nerve roots, the muscles or the connection between them?
• Is one nerve affected (for example at the wrist or elbow) or is the problem widespread?
• Is the damage mainly to the myelin coating or to the nerve fibers?
• How severe is it, and are there signs of ongoing injury or of recovery?

Some findings can be discussed at the end of your visit. In other cases your neurologist will review the results together with your other tests and go over them at a follow-up appointment.

A normal study is also useful information. It can rule out a significant nerve or muscle problem and point the evaluation in a different direction. Very small nerve fibers, which carry pain and temperature sensation, are not well measured by standard nerve conduction studies, so additional tests are sometimes needed.

What Happens After an Abnormal Result?

Treatment depends on the cause. For example, mild carpal tunnel syndrome is often treated with wrist splints at night, activity changes and, in some cases, a steroid injection, while more advanced nerve compression may be referred for surgical release. Neuropathy found on testing usually leads to blood work to look for treatable causes such as diabetes, vitamin B12 deficiency or thyroid disease. A pinched nerve root may be managed with physical therapy, medication and imaging of the spine if needed.

Repeat testing is sometimes recommended months later to check recovery after an injury or surgery, or to monitor a condition over time.

Frequently Asked Questions

Is an EMG safe?

Yes. The electrical pulses are small and brief, and the needle electrodes are sterile and used only once. Serious complications are very rare. Let us know about blood thinners, implanted devices and skin infections ahead of time so that the test can be adjusted if needed.

Do I need someone to drive me?

Usually not. No sedation is used, so most people drive themselves to and from the appointment.

Electrodiagnostic Testing in Westwood, NJ

At our practice, electrodiagnostic testing is performed by neurologists rather than technicians alone. Dr. David D. Van Slooten is board certified in Neurology, Clinical Neurophysiology and Electrodiagnostic Medicine, and Dr. Lorraine S. Lira also performs EMG/NCV studies. Because the physician who examines you is the same one interpreting the results, the test can be tailored to your specific symptoms.

If you are living with numbness, tingling or weakness that has not been explained, an EMG and nerve conduction study can bring clarity and help you and your doctor choose the right treatment. Learn more about our neurology services, or visit our contact page for directions to our Westwood office.

This article is for general education and does not replace advice from your own physician. If you think you are having a medical emergency, call 911.