Pudendal nerve latency. Does it predict outcome of anal sphincter repair?

Electrophysiologic evaluation has been suggested as a means of identifying prognostic factors for patients with fecal incontinence who undergo anal sphincter repair. The purpose of this study was to evaluate the results of anal sphincter repair in patients with documented pudendal neuropathy and to determine the usefulness of electrophysiologic studies for prognostication of sphincteroplasty.

A retrospective review of a series of patients undergoing electrophysiologic studies and anterior anal sphincteroplasty was performed. Data collected included age, standardized incontinence scores (preoperative, immediately postoperative, and current follow-up), and results of pudendal nerve terminal motor latency and monopolar electromyography. Outcomes of sphincteroplasty were designated as excellent, good, fair, or poor based on incontinence scores. Prolonged pudendal nerve terminal motor latency was defined as longer than 2.2 ms and elevated as unilateral or bilateral.

During the time period of the study (1991-1996), 15 patients had electrophysiologic studies and underwent sphincteroplasty. Twelve patients (80 percent) were available for follow-up and form the basis for this study. All patients were women, with a mean age of 45 +/- 18.6 (27-75) years and a mean follow-up of 49.7 +/- 18.6 (20.4-72.6) months. Mean duration of incontinence preoperatively was 13 +/- 16.1 (range, 1-58) years. The incontinence score was 15.8 +/- 3.5 preoperatively, 5.4 +/- 4.5 postoperatively, and 5 +/- 5.1 currently for all 12 patients. There was one patient with normal pudendal nerve terminal motor latency. In the four patients with bilateral prolonged pudendal nerve terminal motor latency, the incontinence scores were 15 +/- 4.2 preoperatively, 8.5 +/- 5.3 postoperatively, and 6 +/- 6.1 (statistically significant compared with preoperation) currently. Seven patients were found to have unilateral prolonged pudendal nerve terminal motor latency with incontinence scores of 16.3 +/- 3.5 preoperatively, 4.4 +/- 3.2 (statistically significant compared with preoperation) postoperatively, and 5.1 +/- 4.9 (statistically significant compared with preoperation) currently. Based on incontinence scores, results of the sphincteroplasty at the most current follow-up were as follows: no neuropathy, excellent in one patient; unilateral neuropathy, five with good/excellent results, two with fair/poor results; bilateral neuropathy, two with good/excellent results, two with fair/poor results (P > 0.05 bilateral vs. unilateral). By monopolar electromyographic examination, external and sphincter denervation was noted in 11 patients; their incontinence scores were 15.5 +/- 3.5 preoperatively, 5.9 +/- 4.3 (statistically significant compared with preoperation) postoperatively, and 5.5 +/- 5.0 (statistically significant compared with preoperation) currently. Monopolar electromyographic results in the puborectalis included four normal examinations and six that were unobtainable. In the two patients with puborectalis denervation, the incontinence scores were 19.5 +/- 0.7 preoperatively, 8.5 +/- 4.9 postoperatively, and 2.5 +/- 3.5 (statistically significant compared with preoperation) currently.

Anterior anal sphincteroplasty in patients with unilateral or bilateral prolonged pudendal nerve terminal motor latency can provide significant improvement in continence with minimum morbidity. Therefore, correction of the anatomic sphincter defect should still be considered, even in patients with documented pudendal neuropathy.