What is the role of muscle signals in sleep stage scoring?

Updated: Aug 19, 2019
  • Author: Andres A Gonzalez, MD, MMM, FACNS; Chief Editor: Selim R Benbadis, MD  more...
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The EMG signals are muscle twitch potentials that may offer additional assistance in defining a sleep stage. Their use is based on the finding that muscle activity decreases during sleep, with muscle activity at its nadir during REM sleep. In many cases, however, appreciating a decreasing muscle tone can be difficult and the relative silence during REM sleep may not be of help in distinguishing it from the preceding or subsequent sleep stages.

Compounding the problem of interpreting EMG channels is intrusion of artifact into the signal. Some examples include cyclic jaw movements, teeth grinding (bruxism), or steady high-amplitude noise generated by increased pressure on an electrode (eg, as caused by lying on the chin). Additionally, muscle artifact spilling over into cortical leads is not an unusual finding. ECG signal is a specific type of cardiac artifact that can appear in all or several channels and can be recognized by tracking the repeating QRS complex throughout the other leads.

Recommended EMG technical requirements include 3 chin EMG electrodes, 2 of which are used throughout the study with an additional lead as a backup.

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