- Nerve vs. Muscle
- Risks and Complications
What are electromyography and nerve conduction studies?
Nerve conduction studies and needle electromyography (EMG) are tests performed to assess the health of nerves and muscles. A neurophysiologist stimulates specific nerves and muscles and studies the resulting activity to evaluate if the nerves and muscles are functioning normally.
A thin needle electrode is inserted into the muscle. The muscle’s electrical activity displays on the EMG’s monitoring device, highlighting to doctors important functional information such as:
- Response to electrode insertion
- Spontaneous electrical activity during rest
- Electrical activity during voluntary muscle movement
Nerve conduction studies
Nerve conduction studies are performed with electrodes placed on the skin to stimulate specific nerves. A mild electric impulse stimulates the nerve, and the resulting neural activity demonstrates how well the nerves are conducting
- Signals of sensation from the tissues to the brain
- Signals from the brain to the muscles to function
What is the difference between EMG and nerve conduction studies?
An EMG test is used to assess if a muscle functions normally when stimulated by its nerve, while nerve conduction studies are performed to test if specific nerves function normally.
Why are EMG and nerve conduction studies performed?
EMG and nerve conduction studies are commonly performed together to diagnose whether a neuromuscular disorder is caused by muscle or nerve damage, in order to accurately diagnose and provide appropriate treatment. These tests are generally performed only when physical examination does not reveal the cause of the disease.
An EMG and nerve conduction studies may be performed when a person has unexplained neuromuscular symptoms such as:
EMG and nerve conduction studies are not performed on people who have
- Temporary external pacing wires for cardiac procedures
- Guidewires for catheter placement
EMG and nerve conduction studies are performed with caution in people who have implanted electrical devices such as:
What do EMG and nerve conduction studies diagnose?
EMG and nerve conduction studies are useful in diagnosing neuromuscular diseases such as:
- Muscular dystrophy: progressive weakness and loss of muscle mass
- Radiculopathy: pain and weakness caused by pinched nerves from herniated discs or degenerative disc disease
- Peripheral neuropathy: nerve pain from damage to peripheral nerves
- Myasthenia gravis: muscle weakness due to problems in the nerve and muscle junction
- Carpal tunnel syndrome: pain, numbness and tingling in the arm due to compressed nerve
- Guillain-Barre syndrome: a condition where the body’s immune system attacks the nerves in the arms and legs
- Charcot-Marie-Tooth disease: an inherited condition which affects the nerves and causes weakness of foot and lower leg muscles
How are EMG and nerve conduction studies performed?
EMG and nerve conduction studies are usually performed by a neurophysiologist, as an outpatient procedure. A technician operates the device while the neurophysiologist studies and interprets the results for a diagnosis. The tests may take one or two hours depending on how many muscles and nerves are tested.
The patient may be required to
- Shower but must not use any lotions or oils on the skin
- Avoid caffeine and sugary beverages for two to three hours prior
- Avoid smoking
- Inform the doctor of any recent infections
- Inform the physician if they have any implanted electrical devices
- The neurologist inserts a thin needle electrode into the muscle that is to be tested.
- The muscle’s electrical activity is transmitted to the EMG machine.
- The neurologist will instruct the patient to flex or relax the muscle.
- The corresponding nerve may also be stimulated to record the muscle’s response.
Nerve conduction studies
- Applies a gel over the skin and places electrodes at different locations along the specific nerves.
- Delivers a small impulse of electric current through the stimulating electrode.
- The other electrodes record the nerve’s response and the time for conduction of the signal.
- The nerve response is recorded in the device and appears on a monitor.
How painful are EMG and nerve conduction studies?
The nerve conduction study may cause a certain amount of discomfort when the mild shock is delivered to the nerve. There usually is no pain after the procedure. The insertion of EMG needle can cause a pain like a muscle injection. The muscle may feel sore for a few days after the test.
What are the risks of EMG and nerve conduction studies?
EMG and nerve conduction studies are low-risk procedures. A very mild electrical impulse is used in the nerve conduction study that is unlikely to cause any harm. With the needle insertion during EMG procedure there may be a small risk of:
- Nerve injury
Top Nerve Conduction Studies and Electromyography Related Articles
Carpal Tunnel SyndromeCarpal tunnel syndrome is a condition in which irritation of the wrist's median nerve causes tingling and numbness of the thumb, index, and middle fingers. Treatment of carpal tunnel syndrome depends on the severity of the symptoms and the nature of any disease that might be causing the symptoms.
Diabetes: Guide to Diabetic Peripheral NeuropathyDiabetes can damage the nerves that help you feel pain, heat, and cold, especially in your feet. Learn about the symptoms of diabetic peripheral neuropathy and the problems it can cause, what you can do about it, and how to prevent it.
Diabetes: Diabetic Peripheral Neuropathy TreatmentThis nerve damage is a common complication of both type 1 and type 2 diabetes. Find out how to prevent it, slow its progression, and deal with symptoms.
Exercises for Diabetes Nerve PainLearn how to cope with the symptoms of diabetic peripheral neuropathy through pain management exercises. Find relief for diabetic nerve pain without medication.
Electromyogram (EMG)Electromyogram or EMG is defined as a test that records the electrical activity of muscles. Normal muscles produce a typical pattern of electrical current that is usually proportional to the level of muscle activity. Diseases of muscle and/or nerves can produce abnormal electromyogram patterns.
Bell's Palsy (Facial Nerve Problems)Bell's palsy is one type of facial nerve paralysis. The seventh cranial nerve controls the muscles of the face, and although scientists do not know the exact cause of Bell's palsy, they think it may be due to nerve damage from an infection, for example, the flu, common cold viruses, and more serious infections like meningitis. The symptoms of Bell's palsy vary from person to person, but can include mild weakness to total paralysis, dry eye, dry mouth, eyelid drooping, drooling, mouth drooping, dry mouth, changes in taste, and excessive tearing in one eye.
Nerve BlocksNerve blocks are used for different pain treatment and management purposes. There are many different types of nerve blocks for specific areas of the body. A plexus or ganglion is a group of nerves that causes pain to a specific area of the body. The pain area is injected with a nerve-numbing substance called a nerve block.
Nerve Conduction Velocity TestA nerve conduction velocity test is an electrical test that detects nerve injury in conditions such as:
- peripheral neuropathy,
- mononeuritis multiplex, and
- compression injuries such as carpal tunnel syndrome and compression neuropathy.
Neuropathic Pain (Nerve Pain)Neuropathic pain is a chronic condition that leads to ongoing pain symptoms. Patients can be predisposed to developing neuropathic pain who have conditions such as diabetes, cancer, stroke, HIV, vitamin deficiencies, shingles, and multiple sclerosis. Patient history and nerve testing are used to diagnose neuropathic pain. Antidepressants, antiseizure medications, and other types of medications are used to treat neuropathic pain. Many people with neuropathic pain are able to attain some level of relief.
Peripheral NeuropathyPeripheral neuropathy is a problem with the functioning of the nerves outside of the spinal cord. Symptoms may include numbness, weakness, burning pain (especially at night), and loss of reflexes. Possible causes may include carpel tunnel syndrome, shingles, vitamin or nutritional deficiencies, and illnesses like diabetes, syphilis, AIDS, and kidney failure. Peripheral neuropathy is diagnosed with exams and tests. Treatment for the condition depends on the cause. Usually, the prognosis for peripheral neuropathy is good if the cause can be successfully treated or prevented.
Pinched NerveA pinched nerve causes pain, numbness, or tingling in the affected area due to pressure on a nerve. Carpal tunnel and sciatica are two examples of conditions caused by a pinched nerve. A pinched nerve is diagnosed by taking a patient history and performing a physical examination. Electromyography may be performed. Treatment for a pinched nerve depends on the underlying cause.
Cervical RadiculopathyRadiculopathy, a condition in which a nerve or nerves along the spine are compressed causing pain, numbness, weakenss, and tingling along the nerve(s). Some causes of radiculopathy include
- bone spurs,
- disc hernation,
- and neuropathy.
- cervical radiculopathy,
- lumbar radiculopathy,
- and thoracic radiculopathy.
Transcutaneous Electrical Nerve Stimulation (TENS)Transcutaneous electrical nerve stimulation (TENS) is a technology that uses a small device to deliver electrical current into tissues to help alleviate pain. TENS is helpful in treating various conditions, including:
- chronic neck pain and
- chronic back pain.
How Do I Get My Sciatic Nerve to Stop Hurting?
Sciatica or sciatic nerve pain is centered on the lower back, and the cause is usually from a ruptured disc in the spinal column that irritates or inflames the nerve.