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Electrodiagnosis is a medical analysis that observes bodily responses from electrical stimulation. A physician generally orders electrodiagnostic testing to determine the cause of pain, weakness or numbness in the back, neck, arms, hands, legs or feet. These tests measure the electrical activity of muscles and nerves to see if there is damage, the cause of the damage and the level of damage.


Electrical Signals and Testing

The nerves and muscles in our bodies create electrical signals to deliver messages to and from the brain. Our nerves send sensory information about our surroundings, and our muscles send motor signals to trigger movement. Certain diseases and injuries can affect the messages our bodies send causing pain, numbness, tingling and strength loss.  There are usually two tests that allow physicians to determine how your muscles and nerves are functioning. A combination of both tests narrow down the possible causes and provides for a better diagnosis.


Nerve Conduction Study (NCS)

This test measures how quick an electrical signal moves through nerves. An NCS identifies nerve damage by checking how fast or slow your nerves are functioning compared to averages. A physician will stimulate your nerves by sending small electrical sensations through electrode patches that have been placed on your skin. Your nerve speed is calculated from the time it takes for the electric signal to move between patches.


Electromyography (EMG)

An EMG tests and records electrical muscle activity to determine if your muscles are receiving signals from your nerves. A physician will place small needles in certain muscles to measure the electrical response. The needles will transmit a tiny electrical current that measures how well your muscles respond. The reaction is recorded and displayed on an oscilloscope in forms of waves. The presence, shape, and size of the wave analyze the ability of your muscle to respond to the electrical stimulation.



Completing an NCS and EMG will allow your physician to learn how your muscles and nerves are functioning and narrow down the possible causes of your symptoms. These tests are designed to and generally can determine nerve injuries and diseases of both the muscles and nerves. Results can include a muscle or nerve disorder, inflammation caused by injury or herniated disc. Depending on your results, your physician will discuss and determine with you the next steps of treatment.

Rakesh Dhar is a medical professional at CNS Multispecialty Clinic and has expertise in electrodiagnostic procedures. Check out his Twitter or read more on his medical overview!