Diagnostic and Prognostic Value of External Anal Sphincter EMG Patterns in Multiple System Atrophy

Background: It is debated whether external anal sphincter (EAS) electromyography can distinguish between multiple system atrophy (MSA) and Parkinson's disease (PD), whereas its usefulness for MSA prognosis is unknown. Objectives: We explored the diagnostic and prognostic value and clinical correlations of EAS electromyography patterns in MSA. Methods: We collected clinical data and EAS electromyography findings in 72 patients with MSA and 21 with PD. Results: We identified four EAS patterns. The normal pattern was frequently observed in PD and associated with prolonged survival when identified in MSA. Abnormal patterns were predominant in MSA. The most severe pattern was associated with the highest likelihood of MSA diagnosis and with the worst prognosis in the MSA cohort. MSA patients with EAS abnormalities often showed urogenital symptoms and fecal incontinence. Conclusions: The increasing severity of EAS electromyography patterns paralleled diagnostic accuracy and survival in MSA, and correlated with prevalence of bladder and bowel symptoms. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.