EMG / NCS Testing
EMG Testing
What is EMG Testing?
- Electromyography (EMG) is a diagnostic procedure to assess the health of muscles and the nerve cells that control them (motor neurons). EMG results can reveal nerve dysfunction, muscle dysfunction or problems with nerve-to-muscle signal transmission.
- Motor neurons transmit electrical signals that cause muscles to contract. An EMG uses tiny devices called electrodes to translate these signals into graphs, sounds or numerical values that are then interpreted by a specialist.
- During a needle EMG, a needle electrode inserted directly into a muscle records the electrical activity in that muscle.
- A nerve conduction study, another part of an EMG, uses electrode stickers applied to the skin (surface electrodes) to measure the speed and strength of signals traveling between two or more points.
What to bring for your EMG/NCS Testing Appointment
- ID & Insurance Cards
- Wear short sleeve shirt or tank top if you are having testing performed on your arms
- Wear or bring shorts if you are having testing performed on your legs
- Do not use lotion on the testing area prior to the test
Why it's done
- Your doctor may order an EMG if you have signs or symptoms that may indicate a nerve or muscle disorder. Such symptoms may include:
- Tingling
- Numbness
- Muscle weakness
- Muscle pain or cramping
- Certain types of limb pain
EMG results are often necessary to help diagnose or rule out several conditions such as:
- Disorders of nerves outside the spinal cord (peripheral nerves), such as carpal tunnel syndrome or peripheral neuropathies
- Muscle disorders, such as muscular dystrophy or polymyositis
- Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis
- Disorders that affect the nerve root, such as a herniated disc
What is NCS Testing?
- 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 brainand spinal cord.
- More specifically, an NCS measures the flow of electrical current through:
- Motor nerves: Nerves that control your musclesand movement.
- Sensory nerves: Nerves that carry signals to your brain about things you touch, taste, smell and see.
What does a nerve conduction study to diagnose?
- Nerve conduction studies help diagnose issues with your peripheral nerves — mainly peripheral neuropathyand 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, vasculitisand Guillain-Barré syndrome. 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.