The Utility of Pudendal Nerve Terminal Motor Latencies in Idiopathic Incontinence

Purpose

Pudendal nerve terminal motor latency testing has been used to test for pudendal neuropathy, but its value remains controversial. We sought to clarify the relationship of pudendal nerve terminal motor latency to sphincter pressure and level of continence in a cohort of patients with intact anal sphincters and normal pelvic floor anatomy.

Methods

We reviewed 1,404 consecutive patients who were evaluated at our pelvic floor laboratory for fecal incontinence. From this group, 83 patients had intact anal sphincters on ultrasound and did not have internal or external rectal prolapse during defecography. These patients were evaluated by pudendal nerve terminal motor latency testing, a standardized questionnaire, and anorectal manometry, which measured resting and squeeze anal pressures. Incontinence scores were calculated by using the American Medical Systems Fecal Incontinence Score. Values were compared by using the Fisher’s exact test and Wilcoxon’s rank-sum test; and significance was assigned at the P < 0.05 level.

Results

1) Using a 2.2-ms threshold, 28 percent of patients had prolonged pudendal nerve terminal motor latency unilaterally and 12 percent bilaterally. 2) At a 2.4-ms threshold, 18 percent of patients had prolonged pudendal nerve terminal motor latency unilaterally and 8 percent bilaterally. 3) Bilaterally prolonged pudendal nerve terminal motor latency was significantly associated with decreased maximum mean resting pressure and increased Fecal Incontinence Score, but not decreased maximum mean squeeze pressure, at both 2.2-ms and 2.4-ms thresholds. 4) Unilaterally prolonged pudendal nerve terminal motor latency was not associated with maximum mean resting pressure, maximum mean squeeze pressure, or fecal incontinence score at either threshold.

Conclusions

The majority of incontinent patients with intact sphincters have normal pudendal nerve terminal motor latency. Bilaterally but not unilaterally prolonged pudendal nerve terminal motor latency is associated with poorer function and physiology in the incontinent patient with an intact sphincter.

Appendix

American Medical Systems Fecal Incontinence Score

In the last four weeks, how often did you experience the following:	Never	Rarely	Sometimes	Weekly	Daily	Several Times Daily
Accidental bowel leakage of gas?	0	1	7	13	19	25
Minor bowel soiling or seepage?	0	31	37	43	49	55
Significant accidental leakage of liquid stool?	0	61	73	85	97	109
Significant accidental leakage of solid stool?	0	67	79	91	103	115
Does accidental leakage affect your lifestyle?	0	1	2	3	4	5
Several times daily (>1 episode/day)
Daily (1 episode/day)
Weekly (<1/day but >1/wk)
Sometimes (>1 in the last 4 weeks but <1/wk)
Rarely (1 in the last 4 weeks)
Never (no episodes in the past 4 weeks)
Score from “Does accidental leakage affect your lifestyle” is added to the highest score from the first four questions
Maximal score = 119