Diagnostic significance of urethral sphincter electromyography and external anal sphincter electromyography in patients with multiple system atrophy

Abstract

Objective To assess the significance of urethral sphincter electromyography (US-EMG) and external anal sphincter electromyography (EAS-EMG) for the diagnosis of multiple system atrophy (MSA). Methods US-EMG and EAS-EMG were performed in 9 patients who were diagnosed as MSA. Duration, motor unit action potentials amplitude, polyphasicity, as well as recruited pattern and amplitude during powerful contraction were recorded and analyzed. Results Among 9 patients who were diagnosed as MSA, 7 cases showed neural injury by both US-EMG and EAS-EMG. There was significant difference of electromyographic findings between US-EMG group and EAS-EMG group (average volatility (μV): 1063.44±499.92 vs 634.89±265.07; polyphasic wave: 0(0,20%) vs 57%(28%,63%); t=2.567，P=0.033；t=2.833，P=0.012). Conclusions Although US-EMG may be difficult to perform, US-EMG may have the same specificity as EAS-EMG for the diagnosis of MSA, especially for the diagnosis of MSA patients only with urination disorders, who are involved in Onuf neclear according to some of the abnormal indexes. Key words: Multiple system atrophy; Urethra; Anal canal; Electromyography