Electromyography and Nerve Conduction Velocity

What Are EMG and NCV?

Electromyography (EMG) and nerve conduction velocity (NCV) tests are diagnostic procedures that measure the electrical activity in muscles and nerves. These tests help doctors detect neuromuscular abnormalities and determine whether muscle or nerve issues are causing symptoms.

Nerve Conduction Velocity (NCV)

A nerve conduction study (NCS), also called NCV, measures how quickly electrical impulses travel through your nerves.

• Surface electrodes are placed on the skin over the nerve.
• One electrode sends a mild electrical impulse, while another records the response.
• The speed and strength of the signal help doctors detect nerve damage or dysfunction.

NCV is often performed along with EMG to provide a complete picture of nerve and muscle health.

Electromyography (EMG)

EMG evaluates the electrical activity of muscles at rest, during slight contraction, and during forceful contraction.

• Small needle electrodes are inserted into the muscle.
• Electrical signals are displayed on a monitor (oscilloscope) and amplified so the activity can be heard.
• The test helps identify whether muscle weakness or abnormal movements are caused by muscle problems, nerve issues, or other factors.

During the test, you may be asked to contract specific muscles (e.g., bending or lifting a limb) to see how your muscles respond to nerve stimulation.

Why Doctors Recommend EMG/NCV

EMG and NCV are often used together to:

• Differentiate muscle disorders from nerve disorders.
• Diagnose the cause of symptoms such as weakness, stiffness, atrophy, or involuntary twitching.
• Evaluate neuromuscular diseases like myasthenia gravis.
• Detect nerve compression or injury, such as carpal tunnel syndrome or sciatica.
• Assess muscle degeneration, such as muscular dystrophy.

Your doctor may also recommend these tests for other reasons based on your symptoms or medical history.

What to Expect During the Tests

• NCV: Small electrodes are placed on the skin. You may feel a mild tingling sensation as the nerve is stimulated.
• EMG: Tiny needles are inserted into the muscle. You may feel slight discomfort, but the procedure is generally safe and well-tolerated.

Both tests provide critical information to help your neurologist develop an accurate diagnosis and personalized treatment plan.