Vaginal pudendal nerve stimulation: a new technique for assessment of pudendal nerve terminal motor latency

Background. To evaluate vaginal stimulation of the pudendal nerve, a new method for investigation of pudendal nerve terminal motor latency (PNTML) and to assess the reproducibility of the method. Methods. Thirteen healthy women and 11 female patients, median age 31 years (range 21–53 years), participated in the study. Ten patients had sustained an anal sphincter rupture and one had idiopathic anal incontinence. Pudendal nerve terminal motor latency was measured after vaginal stimulation of the pudendal nerve with motor response from the pelvic floor and rectal stimulation with motor response from the anal sphincter using the St. Marks pudendal electrode. The women were stimulated by two observers both vaginally and by the rectum. Results. Vaginal PNTML for observer 1 was 2.06 msec (0.50 msec, 2 s.d.) and 2.04 msec (0.55 msec, 2 s.d.) for observer 2, while rectal PNTML was 1.99 msec (0.56 msec, 2 s.d.) and 1.97 msec (0.54 msec, 2 s.d.) respectively. The difference between vaginal and rectal PNTML was 0.065 msec for observer 1 (p=0.106) and 0.070 msec for observer 2 (p<0.05). Degree of agreement between vaginal and rectal PNTML was 80%-116% for observer 1 and 84%-12% for observer 2 (100% represent total agreement between measurements). Interobserver reproducibility for vaginal PNTML was 90%-109% and 86%-113% for rectal PNTML. Conclusion. In clinical practice vaginal PNTML may replace rectal PNTML in women. Reproducibility is in the same range as for rectal PNTML.