Tonic Electromyogram Density In Multiple System Atrophy With Predominant Parkinsonism And Parkinson's Disease

Background: This study aimed to examine whether sleep parameters could provide a method for differentiating multiple system atrophy with predominant parkinsonism(MSA-P)from Parkinson's disease(PD).Methods: The study group comprised 24 MSA-P patients and 30 PD patients,and they were of the similar age,sex,and rapid eye movement(REM)sleep behavior disorder(RBD)prevalence.All patients underwent clinical evaluation and one night of video-polysomnography(vPSG)recording.The tonic and phasic chin electromyogram(EMG)activity were manually quantified during REM sleep of each patient.We divided both groups in terms of whether they had RBD to make subgroup analysis.Results: No significant difference between MSA-P group and PD group had been confirmed in clinical characteristics and sleep architecture.But MSA-P patients had higher apnea hypopnea index(AHI)([1.15(0.00,8.73)] vs.[0.00(0.00,0.55)],P=0.024)and higher tonic chin EMG density(34.02[18.48,57.18]% vs.8.40[3.11,13.06]%,P<0.001)as compared to PD patients.Subgroup analysis found higher tonic EMG density in MSA+RBD than in PD+RBD([55.04(26.81,69.62)] % vs.[11.40(8.51,20.41)]%,P<0.001).Also,no evidence of any difference between PD+RBD and MSA-RBD(P>0.05)in tonic EMG density emerged.Disease duration(P =0.056)and AHI(P =0.051)both showed no significant difference during subgroup analysis,though there was a trend towards longer disease duration in PD+RBD group and higher AHI in MSA-RBD group.Stepwise multiple linear regression analysis identified the presence of MSA-P(?=0.552,P<0.001)and RBD(?=0.433,P<0.001)as predictors of higher tonic EMG density.Conclusions: Tonic chin EMG density could be a potential marker for differentiating MSA-P from PD.