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

The LEMG procedure may be somewhat uncomfortable. However, it is generally not time-consuming, and takes from 5 to 20 minutes.

• If the approach to the voice box muscles is through the skin of the neck (transcutaneous approach), the patient will be lying down with the neck slightly extended.
• If the approach to the voice box muscles is through the mouth using a viewing tube called an endoscope (transoral or endoscopic-guided approach), the patient will be sitting upright in an examination chair.

• The patient's skin is cleaned to remove bacteria, oil, and make-up.
  • Depending upon the type of electrode to be used, the skin on the chin and/or forehead may also be cleaned with alcohol to allow for good contact with surface electrodes.
  • Sometimes, conducting jelly or cream will applied to the skin where the surface electrodes will be placed.
• Some doctors may inject a small amount of local anesthesia into the skin above the voice box to make the LEMG procedure more comfortable. The anesthesia injection feels like a pinprick and often causes a brief burning sensation.

Key Information

A Note on Local Anesthesia

Local anesthesia is not used by all doctors who perform LEMG because the local anesthetic may change the results of the LEMG.

LEMG recording needles (recording electrodes) are inserted into each voice box muscle to be studied. LEMG recording needles are fine needles, like acupuncture needles. Patients undergoing LEMG often report a feeling of pressure rather than sharp pain.

Recording of insertional activity: As each needle is inserted, the voice box muscle entered will give off electrical discharges – referred to as "insertional activity."

Recording of spontaneous activity: After insertional activity is recorded and "quiets down" as the muscles overcome the initial reaction to the needle, the patient is asked to remain as still as possible (no talking, no swallowing). Muscle electrical discharges that spontaneously occur during this quiet period – referred to as "spontaneous activity" – are then recorded.

Recording of voluntary activity: Electrical discharges during specific muscle action(s) done by the patient – referred to as "voluntary activity" – will then be recorded.

• The patient is asked to talk, swallow, sniff, or say "eee" – first with a low level of force, so the electrical signals associated with a "minimal voluntary contraction" can be evaluated, and then with a lot of force, to allow evaluation of a "maximum contraction."
• The tasks patients will be asked to do are specific to the investigation of certain voice box muscles, since each muscle has a different role in different voice tasks. (For more information, see Anatomy & Physiology of Voice Production.)

• Typically, all four key voice box muscles need to be evaluated.
• When only one side is abnormal, LEMG may still be done on the normal side to serve as a reference and to provide information regarding the nature and extent of the voice disorder.
• The needles usually need to be re-adjusted several times during the procedure.

During the examination, patients may hear noisy sounds as the muscles are contracting. These sounds are normal. Some sounds are similar to electrical static noise. In addition,

• "Seashell sounds" reflect the random, miniature chemical connections that occur between the nerve and muscle; these represent normal findings
• "Sputtering fat in a frying pan" sounds result from the spikes in action current close to a nerve-muscle connection; these represent normal findings

To test the different muscles of the larynx, LEMG recording needles are placed exactly into the mid-portion or "belly" of the particular muscle being studied. Patients are then asked to perform different voice actions that cause the muscle to contract. During this time, all electrical discharges are recorded and evaluated.

The muscles of the larynx are generally named for the cartilages in the larynx to which they connect. These names are rather long and cumbersome, and are therefore often referred to by abbreviations only. (For more information, see Anatomy & Physiology of Voice Production.)

Muscles of the Larynx

Specific Muscle	Specific Location		Specific Task
Set of Muscles (m) on Each Side	Two Cartilage Connections		Voice Box Function	Nerve Input	LEMG Task
Thyroarytenoid (TA) m	Thyroid	Arytenoid	Collectively work to bring vocal folds together for voice production, swallowing	RLN	"eeee"
Interarytenoid (IA) m	Left arytenoid	Right arytenoid
Lateral cricoarytenoid (LCA) m	Cricoid	Arytenoid
Cricothyroid (CT) m	Cricoid	Thyroid	Adjust pitch of voice	SLN	low to high "eeee"
Posterior cricoarytenoid (PCA) m	Cricoid	Arytenoid	Open the vocal folds during breathing, sniffing	RLN	sniff
RLN = recurrent laryngeal nerve; SLN = superior laryngeal nerve

The muscles that bring the vocal folds together are the thyroarytenoids (TA), interarytenoids (IA), and lateral cricoarytenoids (LCA). These muscles, referred to as "adductors":

• Bring the left and right vocal folds together at the midline of the airway
• Produce tension in the vocal folds to allow voice production
• Help to bring the vocal folds together during swallowing to prevent the passage of food and liquids into the windpipe

To test these adductor muscles, patients are asked to say a prolonged "eeeee," repeat a certain sound, or hold their breath.

The cricothyroid (CT) muscle helps increase voice pitch. To test this muscle, patients are asked to say a prolonged "eeee" sound, but this time starting at a very low pitch and then going to a very high pitch, all with one breath.

The posterior cricoarytenoids (PCA) are the only muscles in the larynx that open the vocal folds or move the vocal folds away from the midline of the airway. The PCA muscles are therefore referred to as "abductors." The PCA muscles are located in the back of the larynx and accessing them is more difficult than most of the other laryngeal muscles. To induce abduction of the vocal folds, patients are asked to sniff.

Key Information

LEMG on the PCA muscles is usually unnecessary. All four nerves responsible for movement-inputs to voice box muscles (right and left recurrent laryngeal nerves, right and left superior laryngeal nerves) can be evaluated on LEMG by testing just four muscles:

• Right and left cricothyroid (CT) muscles
• Right and left thyroarytenoid (TA) muscles

What does a patient experience following LEMG?

After LEMG, patients usually experience the following:

• Slight discomfort from the needle placement
• Slight bruising in the area
• Vocal fold swelling, temporarily causing slight hoarseness

Advisory Note