Pudendal neuropathy is not related to physiologic pelvic outlet obstruction

Chronic straining because of pelvic outlet obstruction is hypothesized to cause pudendal neuropathy (PN) by stretch injury.

The aim of this study was to determine any association between PN and pelvic outlet obstruction.

One hundred forty-seven constipated patients were evaluated by cinedefecography and pudendal nerve terminal motor latency assessment. PN was defined as a latency longer than 2.2 ms. Pelvic outlet obstructive patterns of evacuation included paradoxic contraction, nonrelaxation of the puborectalis muscle, or failure of opening of the anal canal.

Median length of constipation including straining during evacuation was eight (range, 1-47) years. Ninety-one (62 percent) subjects had a normal pattern of evacuation, and 56 (38 percent) had an obstructed pattern. Both groups had a similar median age (68 vs. 69 years, respectively; P > 0.05) and same median length of symptoms. Overall incidence of PN was 23.8 percent (10.9 percent unilateral and 12.9 percent bilateral). There was no difference in the incidence of PN between patients with normal evacuation and patients with obstructed evacuation (24.2 percent vs. 23.2 percent, respectively; P > 0.05). Patients with PN had a similar incidence of physiologic pelvic outlet obstruction as did patients without PN. However, median age of patients with PN was higher than those without PN (73 vs. 66 years, respectively; P > 0.05).

There was a difference in the incidence of PN between normal and obstructed patterns of evacuation. Therefore, the espoused theory that obstructed defecation causes PN appears flawed.