On-line quantitative analysis of surface electromyography of the pelvic floor in patients with faecal incontinence

Background: Needle electromyography (EMG) remains the ‘gold standard’ for the assessment of external anal sphincter innervation. It is, however, an invasive and poorly tolerated technique. In this study a quantitative form of surface electromyography was compared with needle EMG of the external anal sphincter. Methods: Invasive needle EMG to assess mean fibre density and neuromuscular jitter was compared directly with quantitative surface EMG in 37 patients with faecal incontinence and 12 age‐matched controls. Results: There was a significant positive correlation between mean fibre density on needle EMG and maximum turns rate on surface EMG (r s = 0·48 (95 per cent confidence interval 0·28–0·76), P = 0·003). Furthermore, surface EMG was able to discriminate between patients with normal neuromuscular jitter and those with increased jitter, a measure of progressive denervation and reinnervation, on the basis of reduced rectified mean surface signal (P = 0·02, Fisher's exact test). Conclusion: Quantitative surface EMG may potentially replace invasive needle EMG as the investigation of choice in the assessment of anal sphincter electrophysiology. © 2000 British Journal of Surgery Society Ltd