Method: The current case-control study compares a large sample of women suffering from chronic myofascial TMJD (n=124) with a demographically matched control group without TMJD (n=46) on sleep background electromyography (EMG) during a laboratory PSG study. Background EMG activity was measured as EMG root mean square (RMS) from the right masseter muscle after lights out. Sleep background EMG activity was defined as EMG RMS remaining after activity attributable to SB, other orofacial activity, other oromotor activity and movement artifacts were removed.
Result: Results indicated that median background EMG during these non SB-event periods was significantly higher (p<.01) for women with myofascial TMJD (median=3.31 µV and mean=4.98 µV) than for control women (median=2.83 µV and mean=3.88 µV) with median activity in 72% of cases exceeding control activity. Moreover, for TMD cases, background EMG was positively associated and SB event-related EMG was negatively associated with pain intensity ratings (0-10 numerical scale) on post sleep waking.
Conclusion:
These data provide the foundation for a new focus on small, but persistent, elevations in sleep EMG activity over the course of the night as a mechanism of myofascial TMJD pain induction or maintenance.