The SINBAR EMG, percentage of RWA from mentalis tonic and any activity, and percentage of RWA from FDS phasic activity all correlated with both disease duration and levodopa-equivalent dose.
Birgit Hogl, MD
Using the Sleep Innsbruck Barcelona (SINBAR) electromyographic (EMG) montage (including the mentalis, flexor digitorum superficialis, and extensor digitorum brevis), researchers recently concluded that REM sleep without atonia (RWA) is higher in mentalis and flexor digitorum superficialis muscles (FDS) in patients with advanced stage Parkinson disease (PD) versus early-stage patients.
Senior author Birgit Hogl, MD, neurologist and sleep specialist, Medical University Innsbruck, and colleagues concluded, “our findings suggest that RWA worsens or is more intense or more frequent with disease progression.”
Thirty patients with PD (15 early-stage or drug-naïve and 15 advanced stage) were recruited for this study. No significant differences were present between early- and advanced-stage patients with PD, except for REM sleep latency in early-stage PD, which was significantly shorter than advanced-staged PD (85.4 min [±46.2] vs 160.6 min [±118.5]; P = .034).
Early-stage PD was defined as treatment-naïve or having no motor complications with diagnosis within the previous 6 years. Advanced PD was defined as a disease duration equal to or more than 6 years with or without motor complications.
Regarding RWA analysis, the mean percentage of all patients with PD was 47.2 (±24.5). Hogl and colleagues found significant differences between early- and advanced-PD on both tonic EMG activity in the mentalis muscle (3.9 [±12.1] vs 26.2 [±27.8]; P = .010) and the SINBAR EMG index (37.5 [±19.1] vs 57.0 [±26.0]; P = .026).
Phasic EMG activity of FDS (17.0 [±8.5] vs 30.3 [±23.2]; P = .052) and any EMG activity in the mentalis muscle (22.5 [±13.4] vs 31.1 [±13.0]; P = .084) were lower in early-stage PD than advanced-stage PD.
Researchers noted that the effects of severe RWA can predict the early development of dementia with Lewy bodies and PD, but that only a few studies have investigated RWA in different PD stages. This study aimed to evaluate and characterize tonic, phasic, and any EMG activity during REM sleep by using the SINBAR EMG montage including chin and upper extremity muscles in PD, and compared them by stages.
The higher levels of tonic EMG activity, phasic EMG activity, and SINBAR EMG index observed in advanced-stage PD did not change when excluding patients taking antidepressants. Additionally, there was no significant differences in phasic EMG activity in the TA muscle when comparing the 2 stages of PD.
"The correlation of both tonic EMG activity of the mentalis muscle and phasic EMG activity of FDS muscle with longer disease duration indicates the involvement of different pathways in evolving alpha-synuclein related neurodegenerative disease,” Hogl et al wrote.
Eleven patients (36.7%) had a history of dream enactment or vocalization during sleep, 5 of which were in the early-PD group and 6 in the advanced-PD group. Among patients with no history of dream enactment, 68.4% (13 of 19) had RWA over the SINBAR cut-off. Of these, 47.4% (9 of 19) were diagnosed with RBD based on video-polysomnography.
Percentage of RWA from mentalis tonic and any activity, SINBAR EMG index, and percentage of RAW from FDS phasic activity correlated with both disease duration and levodopa equivalent dose (LED), with the highest correlation found for the SINBAR index (disease duration r = .508; P = .004; LED r = .617; P = .001). Notably, disease duration also showed significant correlation with total LED (r = .635; P <.001).
This research abstract was published recently in an online supplement of the journal Sleep. The findings also will be presented in June at Virtual Sleep 2021, the 35th annual meeting of the Associated Professional Sleep Societies.