LEMG: Highlights

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Key Glossary Terms

Laryngeal Electromyography (LEMG)
A test that measures the electrical discharges from voice box muscles during activities such as speaking, breathing, and swallowing

Paresis
Partial paralysis; partial loss of nerve input to a muscle, resulting in muscle weakness

Paralysis
Complete loss of nerve input to a muscle, resulting in complete loss of muscle function

Motor Unit
The functional unit made up of all muscle fibers that receive nerve inputs from a single nerve cell; a muscle is made of many motor units

Glossary

Laryngeal Electromyography (LEMG) is a medical procedure that records the electrical activity produced by voice box muscles in action. LEMG gives specific information as to whether the nerve input into a particular muscle is normal or abnormal. During LEMG, electrical activity is recorded, amplified, and displayed on a screen and/or played on a loudspeaker to allow visual and sound analysis.

Nerve input is necessary for muscles to move. Nerve input is an electrical impulse that triggers electrical activity in the muscle fibers connected to the nerve. Electrical activity then spreads throughout the muscle and causes chemical changes, which lead to muscle contraction or movement. Muscle movement is associated with electrical activity; muscle contraction itself does not produce electrical activity.

LEMG can give detailed information that helps in the investigation of voice disorders caused by partial loss (paresis) or complete loss (paralysis) of nerve input.

• It can play an important role in the identification of a nerve problem as the cause of a patient's voice disorder.
• It can help guide treatment strategies.
• It can help identify which nerves are abnormal.
• It can help predict the possibility for recovery or the risk of permanent loss of nerve function.

LEMG is performed in the clinic with the help of a laryngologist, a neurologist, and/or technician – all members of the voice care team. There is no electric shock. Through the use of special fine needles (electrodes), LEMG measures electrical activity during muscle activity in certain voice box muscles.