Clinical Significance of Amplitude in Pudendal Nerve Conduction Study in Patients with Defecation Disorders

Joo, Jae Sik; Kim, Jae Do

Abstract

Many different kinds of anorectal physiologic studies were performed for the evaluation of defecation disorders. Some of these studies are anorectal manometry and pudendal nerve conduction study. In pudendal nerve conduction study, pudendal nerve terminal motor latency (PNTML) was considered to be very useful for the evaluation and management of these patients. However, evaluation of amplitude in pudendal nerve conduction study has been clinically seldom used. Therefore, the aim of this study was to evaluate the clinical significane of amplitude in pudendal nerve conduction study in patients with defecation disorders by comparing to manometric profiles. MATERIAL AND METHODS: Between February, 1997 and February, 1998 all patients who underwent pudendal nerve conduction study and anorectal manometry for the evaluation of defecation disorders (constipation and fecalincontinence) were analyzed. Latency as well as amplitude in pudendal nerve conduction study were compared in both groups to the pressure profiles in manometric study according to the subgroups of these patients. Statistical analysis were performed by a Chi-square or Student's t-test and significance was assumed when p<0.05.
RESULTS
A total of 80 patients, forty constipation with a mean age of 55.3+/-14.5 (GI: range; 24~86) years and forty fecal incontinence with a mean age of 61.1+/-10.3 (GII: range; 37~74) years and a male to female ratio of 25:15 (GI), 28:12 (GII), were studied. PNTML in both sides in GI were significantly decreased in comparision to those of GII (GI: Rt, 2.17+/-0.7 ms Lt, 2.03+/-0.5 ms, GII: Rt, 2.50+/-0.7 ms, Lt 2.64+/-0.8 ms, p<0.05), However, there were no differences between the two groups in terms of amplitudes (GI: Rt 399.0+/-348 uV, Lt 426.8+/-403 uV, GII: Rt, 406.9+/-273 uV Lt, 392.9+/-291 uV, NS) in pudendal nerve conduction study. In manometric findings, even though maximal resting, mean, minimum and maximal pushing pressures were no differences in both groups, mean resting and maximal squeezing pressure were significantly increased in GI than those of GII (GI: 82.4+/-31 cmH20, GII: 60.5+/-25 cmH20 in mean resting pressure, GI: 213.1+/-108 cmH20, GII: 178.7+/-66 cmH20 in maximal squeezing pressure, p<0.05) When we analyzed the overall values of amplitudes according to the diagnosis, age, gender, and the value of PNTML, there were no statistically significant differences between the two groups. But, when the one side of PNTML shorter than the other side, it tended to have a high amplitude in that side than that of the other side in the same patient (the probability for trend was 74%).
CONCLUSION
Constipation patient has a shorter PNTML, higher mean resting, and maximal squeezing pressure than fecal incontinene patient. The amplitude in pudendal nerve conduction study had a trend of inverse correlation to the latency in the same patient. Therefore, amplitude in pudendal nerve conduction study might be useful to monitor or predict the outcome after treatment in patients with defecation disorders.