Variation in pudendal nerve terminal motor latency according to disease

PURPOSE: The aims of this study were first to establish whether any difference among pudendal nerve terminal motor latency (PNTML) values exists relative to diagnosis, second to determine whether left and right latencies are similar, and third to assess any correlation between age and neuropathy. Latency was elicited three times on each side, and an average latency was recorded as a result. MATERIALS AND METHODS: Between June 1989 and April 1995, 1,026 patients (775 females and 251 males) underwent PNTML study. These patients were divided into four groups according to diagnosis: Group I, fecal incontinence; Group II, chronic constipation; Group III, idiopathic rectal pain; Group IV, rectal prolapse. Overall mean age was 61.5 (range, 6-95) years. Student's t-test was used to calculate statistical differences. Patients were then analyzed according to age and gender. Correlation was calculated with the nonparametric Mann-Whitney U test. RESULTS: Unilateral or bilateral prolongation of PNTML was noted in 90 patients (21.2 percent) in Group I, 80 (20.4 percent) in Group II, 22 (18.1 percent) in Group III, and 38 (42.6 percent) in Group IV. Average PNTML on the left side was 1.88 ms in Group I, 1.94 ms in Group II, 1.98 ms in Group III, and 2.12 ms in Group IV. Average PNTML on the right side was 1.85 ms in Group I, 1.94 ms in Group II, 1.99 ms in Group III, and 2.07 ms in Group IV. The only statistically significant differences in PNTML were between Groups I and IV (left, P < 0.005; right, <0.05) and between females and males (P < 0.0001). CONCLUSION: There is no statistically significant difference between latencies of left and right pudendal nerves. Similarly, there are no statistically significant differences among patients with fecal incontinence, chronic constipation, or chronic idiopathic rectal pain. Normal latency can be expected in patients with constipation or fecal incontinence. However, patients with rectal prolapse have a more prolonged PNTML. Age is correlated with a higher incidence of pudendal neuropathy. This study reveals significant overlap among PNTML values and diagnosis.