Which parameter is measured to assess muscle tone during sleep?

The measurement of muscle tone during sleep is specifically evaluated using an electromyogram (EMG). The EMG records electrical activity in the muscles and provides valuable information about muscle tension. During different sleep stages, particularly REM sleep, muscle tone can significantly decrease, which is indicated by low or absent EMG activity. This aspect is crucial for identifying sleep disorders such as REM sleep behavior disorder, where the normal paralysis of skeletal muscles does not occur.

In contrast, an electrocardiogram (ECG) measures heart electrical activity and is not suited for assessing muscle tone. Pulse oximeter readings monitor oxygen saturation in the blood and do not provide information about muscle activity. Similarly, an electroencephalogram (EEG) records brain wave patterns, which relates to brain activity rather than muscle tone. Hence, the EMG is the most appropriate parameter for evaluating muscle tone during sleep.