Role of external anal sphincter electromyography for differential diagnosis of multiple system atrophy, Parkinson's disease and late-onset spinocerebellar ataxia

Abstract

Objective To observe the electrophysiological changes, especially in the examination of external anal sphincter electromyography ( EAS-EMG), with those patients diagnosed as multiple system atrophy ( MSA), Parkinson's disease (PD) and late-onset spinocerebellar ataxia (LOSCA) and explore its clinical diagnostic value as well as differential diagnostic value for the three diseases. Methods The clinical data, cranial magnetic resonance imaging (MRI) data as well as results of EAS-EMG for 3 groups patients, including 88-cases MSA, 69-cases PD and 18-cases LOSCA, were analyzed retrospectively.Results EAS-EMG showed that 84 cases (95.5%) in MSA group had varying degrees of neurogenic injury. Meanwhile, mean motor unit potentials (MUPs) duration (( 12.92 ± 2.59)ms), mean MUPs amplitude ( ( 648.6 ± 251.0 ) μV ), and MUPs polyphasicity ( percentage of polyphasic MUPs; 42. 6% ±21.2% ) in MSA group were significantly different from those in PD ( ( 8. 99 ± 0. 47 ) ms, (470. 0 ±91.9) μV, 24.2% ±11.0%) and LOSCA groups ((9.04 ±0.62)ms, (493.1 ± 113.7)μV,22.0% ±12. 1%; Welch:94. 240,18. 093,26. 710,all P =0. 000). The spontaneous potentials and satellite potentials showed more common in MSA group, but not in other groups. Conclusions MSA and PD and LOSCA are easily mutually misdiagnosed because of some similar syndromes, but the method of EAS-EMG could be effective and helpful to enhance accurate diagnostic rate of MSA and its differential diagnosis with PD and LOSCA. Key words: Multiple system atrophy ; Parkinson disease ; Spinocerebellar ataxias ; Anal canal ; Electromyography ;