Comparative Study of Diagnostic Significance of Urethral Sphincter Electromyography and External Anal Sphincter Electromyography in Patients with Multiple System Atrophy

Objectives: to evaluate the diagnostic value of external anal sphincter electromyography (EAS-EMG) and urethral sphincter electromyography (US-EMG) in patients with multiple system atrophy (MSA). Methods: 35 patients who were diagnosed as MSA were examined as treatment group, while 53 non-MSA patients were examined as control group, using EAS and US-EMG. Data was recorded and analyzed, including spontaneous activities when relax, parameters of mean moter unit potential (MUP) duration and amplitude, MUP polyphasicity (percentage of polyphasic MUP) and variation when strong contraction. Results: Neurogenic injury was showed in US-EMG and EAS-EMG in 27 cases of MSA group (77.1%). There were significant differences for MUP duration between MSA and non-MSA cases by both EAS-EMG (t=3.515, P=0.001) and US-EMG (t=3.489, P=0.002). Meanwhile, MUP polyphasicity showed significant difference between MSA and non-MSA cases by EAS-EMG only (t=2.511, P=0.016). EAS-EMG showed more significant changes in neurogenic injury than US-EMG. Conclusions: Both US-EMG and EAS-EMG are useful for the diagnosis of MSA. The differences of multiple indexes of EAS-EMG were more significant than those of US-EMG for MSA cases. US-EMG could be a supplement of EAS-EMG in case of restriction.