Percutaneous nerve evaluation based on electrode placement under control of autonomic innervation

Background Foramen needle electrode placement for percutaneous nerve evaluation (PNE) is currently carried out while observing the somatic motor response. This study investigated electrode placement while observing the autonomic as well as the somatic response. Methods A consecutive series of ten patients (seven women) with a median age of 51.9 (range 30–75) years undergoing PNE for faecal incontinence ( n = 6) and obstipation ( n = 4) were investigated prospectively. Electrode placement was carried out under simultaneous electromyography (EMG) of the external anal sphincter (EAS) and internal anal sphincter (IAS) and cystomanometry. Results PNE under control of somatic and autonomic nerve responses was carried out in all patients. In three out of ten patients, initial needle electrode placement showed single evoked EMG signals from the EAS. Final electrode placement resulted in adequate somatic motor and autonomic responses in all patients. Comparison of the increases in IAS EMG amplitude on the right and left stimulation sites for sacral nerves S3 and S4 demonstrated significant differences [S3 right: median 15.3 (interquartile range (IQR) 10.4; 20.1) µV vs. S3 left: median 11.6 (IQR 8.6; 16.0) µV, p = 0.034 and S4 right: median 24.1 (IQR 20.1; 37.2) µV vs. S4 left: median 12.0 (IQR 10.7; 13.7) µV, p = 0.012]. Stimulation-induced bladder activation was achieved in all seven patients with concomitant urinary dysfunction. Conclusions Control of not just the somatic motor response but also the autonomic nerve response during foramen needle electrode placement may objectify PNE.