Differential Diagnosis Of Multiple-System Atrophy With Parkinson’s Disease By External Anal- And Urethral-Sphincter Electromyography

Figures & data

Table 1 Sex, Age, And Course Of Disease Between MSA And PD Groups

	MSA (n=101)	PD (n=100)	Statistics	P-value
Sex (male)	52	65	χ^2=3.773	^#0.052
Age, years	56 (52–64.5)	64.7±10.0	Z=−4.566	*<0.001
Course of disease, years	2.4 (1.5–4.0)	3.0 (1.075–5.0)	Z=−0.633	*0.527

Notes: *Mann–Whitney U test used for analysis because data were not of standard normal distribution; ^#Pearson χ².

Abbreviations: MSA, multiple-system atrophy; PD, Parkinson’s disease.

Table 2 EAS-EMG Results Between MSA And PD Groups

	MSA (n=99)	PD (n==100)	Statistics	P-value
MUP duration, ms	12.2 (10.9–13.5)	9.8 (9.425–10.55)	Z=−8.557	*<0.001
MUP amplitude, μV	465 (374–613)	481 (350–586.75)	Z=−0.752	*0.452
Percentage of polyphasic MUPs	37.1 (23.5–56.3)	31.6 (21.825–37.325)	Z=−3.556	*<0.001
Amplitude during strong contractions, mV	1.1 (0.9–1.5)	1.45 (1–2)	Z=−2.840	* 0.005
Ratio of simple phase and simple-mix phase, %	38.4	9.0	χ^2=23.810	^#<0.001

Notes: *Mann–Whitney U test used for analysis because data were not of standard normal distribution; ^#Pearson χ².

Abbreviations: EAS-EMG, external anal-sphincter electromyography; MUPs, motor unit potentials; MSA, multiple-system atrophy; PD, Parkinson’s disease.

Figure 1 EAS-EMG and US-EMG of patients with MSA.

Notes: (A) Prolonged MUP duration and increased percentage of polyphasic MUPs were detected by EAS-EMG in MSA group. (B) Prolonged MUP duration was detected by US-EMG in MSA group.
Abbreviations: EAS-EMG, external anal-sphincter electromyography; US-EMG, urethral-sphincter electromyography; MSA, multiple-system atrophy; MUPs, motor unit potentials.

Table 3 US-EMG Results Between MSA And PD Groups

	MSA (n=81)	PD (n=96)	Statistics	P-value
MUP duration, ms	11.5 (10.3–13.1)	9.8 (9.3–10.575)	Z=−6.996	*<0.001
MUP amplitude, μV	290 (232–422)	296 (235.25–380.25)	Z=−0.159	*0.874
Percentage of polyphasic MUPs	14.3 (0–30.8)	14.3 (0–22)	Z=−1.046	*0.296
Amplitude during strong contractions, mV	0.8 (0.5–1.2)	0.8 (0.6–1.475)	Z=−1.320	*0.187
Ratio of simple phase and simple-mix phase, %	45.7	10.4	χ^2=28.010	^#<0.001

Notes: *Mann–Whitney U test used for analysis because data were not of standard normal distribution; ^#Pearson χ².

Abbreviations: US-EMG, urethral-sphincter electromyography; MUPs, motor unit potentials; MSA, multiple-system atrophy; PD, Parkinson’s disease.

Table 4 Comparison Of Indices Obtained In EAS-EMG And US-EMG Of MSA Group

	EAS-EMG (n=99)	US-EMG (n=81)	Statistics	P-value
MUP duration, ms	12.2 (10.9–13.5)	11.5 (10.3–13.1)	Z=−1.450	*0.147
MUP amplitude, μV	465 (374–613)	290 (232–422)	Z=−6.795	*<0.001
Percentage of polyphasic MUPs	37.1 (23.5–56.3)	14.3 (0–30.8)	Z=−6.461	*<0.001
Amplitude during strong contractions, mV	1.1 (0.9–1.5)	0.8 (0.5–1.2)	Z=−4.206	*<0.001
Ratio of simple phase and simple-mix phase, %	38.4	45.7	χ^2=0.975	# 0.323

Notes: *Mann–Whitney U test used for analysis because data were not of standard normal distribution; ^#Pearson χ².

Abbreviations: EAS-EMG, external anal-sphincter electromyography; US-EMG, urethral-sphincter electromyography; MUPs, motor unit potentials; MSA, multiple-system atrophy.

Table 5 Cutoff Points, Area Under ROC curve, Sensitivity, Specificity, And 95% CIs Of Some Parameters In EAS-EMG And US-EMG For Differentiating MSA From PD

	EAS-EMG					US-EMG
	Cutoff Point	AUC	Sen, %	Spe, %	95% CI	Cutoff Point	AUC	Sen, %	Spe, %	95% CI
MUP duration	10.9 ms	0.851	75.8	83	0.797–0.905	11.1ms	0.805	63	86.5	0.741–0.870
Percentage of polyphasic MUPs	40.9	0.646	42.4	93	0.567–0.724	—	—	—	—	—

Abbreviations: EAS-EMG, external anal-sphincter electromyography; US-EMG, urethral-sphincter electromyography; MUPs, motor unit potentials; MSA, multiple-system atrophy; PD, Parkinson’s disease; AUC, area under ROC curve; Sen, sensitivity; Spe, specificity.

Figure 2 ROC curves for MSA and PD in EAS-EMG and US-EMG.

Notes: (A) ROC curve for differential diagnosis of MSA with PD according to mean MUP duration and percentage of polyphasic MUPs in EAS-EMG. (B) ROC curve for differential diagnosis of MSA with PD according to mean MUP duration in US-EMG.
Abbreviations: ROC, receiver-operating characteristic; EAS-EMG, external anal-sphincter electromyography; US-EMG, urethral-sphincter electromyography; MSA, multiple-system atrophy; PD, Parkinson’s disease; MUPs, motor unit potentials.