Why LEMG Is Done
 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
Why is LEMG examination important?
In
the investigation of certain voice disorders, LEMG results can have a
substantial impact on a patient's clinical care. LEMG is often
performed when the cause or causes of abnormal or absent vocal fold
movement need to be found. (For more information, see Vocal Fold Paresis/Paralysis.)
Specific Information
An LEMG is the most specific neurologic test of voice function. An LEMG can provide:
- Electrical information on voice box muscles
- Neurological information as to the need for additional testing and/or specific treatments for laryngeal paresis/paralysis
Specific Roles in Identifying Causes of Voice Disorders
Role in diagnosis of vocal fold immobility: LEMG provides
specific information about nerve inputs to voice box muscles. This
information is important when movement of one or both vocal folds is
abnormal, decreased, or absent. The presence of normal nerve inputs
would indicate that vocal fold non-movement is most likely due to a
joint problem (arytenoid fixation) or to abnormal tissue growth that
impedes motion (as in subglottic stenosis),
rather than due to a complete loss of nerve input (as in paralysis).
Since treatment strategies will differ depending on the cause of vocal
fold non-movement, using LEMG to determine the cause is important.
Role in other neurological diseases affecting voice: LEMG can assist in the identification of suspected neurological disorders, such as:
- Laryngeal tremor
- Myasthenia gravis
- Amyotrophic lateral sclerosis (ALS)
Role in swallowing disorders: LEMG can also be useful in the
investigation of voice box muscles after an injury, as well as in the
analysis of the involvement of voice box muscles in patients with a
swallowing disorder.
Assessing Potential for Recovery (Prognosis)
LEMG can provide insight into whether recovery of nerve function can be expected.
- If LEMG results suggest that improvement is likely with voice therapy, surgery may be delayed.
- If
LEMG results indicate that no further recovery can be expected absent
surgical intervention, surgery may be scheduled right away.
 Key Information
Botulism Toxin Injections to Voice Box Muscles
LEMG
is also used as a guiding tool for placing botulinum toxin injections
into specific voice box muscles in patients with spasmodic dysphonia.
During these injections, the needle used to inject the toxin also
serves to measure the electrical discharge from the voice box muscle (EMG electrode). (For more information, see Spasmodic Dysphonia.)
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