Electromyography or EMG is a technique that is used to evaluate and record the electrical activity of the skeletal muscles. The nerves in your skeletal muscles transmit messages when the muscles contract and relax. Electromyography is performed using an instrument called electromyograph. This helps determine the causes for nerve disorders and muscle weakness. EMG is done to assess the overall health of skeletal muscles and the nerves controlling them.
How is an EMG done?
Signals from the nerve cells that stimulate the muscles are called motor neurons. This stimulation leads to electrical activity in the muscle and which then causes the muscle to contract. This is how the electric signals are produced.
A thin needle electrode is inserted into the muscle through the skin. This would feel like a needle prick. The electrical activity in your muscle is picked up by the electrode in the needle. The electrode is connected to a special monitor called the Oscilloscope which displays the readings. The results can then be printed or saved on the computer.
Purpose of EMG
EMG helps in diagnosing:
- Nerve compression
- Nerve injury
- Nerve root injury
- Damage to the muscle
- Damage to the neuromuscular junction (Connection between a muscle and it’s nerve fiber)
The results can be viewed immediately after the electrodes are inserted. The muscle needs to be contracted for the electrical activity to appear on the Oscilloscope. A gradual increase in the contraction provides varying rates and amplitudes of electrical activity. A trained medical specialist or a neurologist can analyze and interpret the results.