THE NEUROPHYSIOLOGICAL SIGNIFICANCE OF PERINEAL DESCENT

The establishment of a linear relationship between perineal descent (P D) and pudendal nerve motor terminal latency (PNMTL) is important in u nderstanding the pathophysiology of pudendal neuropathy. The amount of stretching of the pudendal nerve resulting from the extent of PD, sho uld correlate with the amount of injury sustained (PNMTL). The two key previous studies which used different techniques to measure PD, have differed on this vital issue. A prospective study was undertaken in 14 1 consecutive patients with PD (M:F = 57:84; mean age 46.3 SEM 1.6 yea rs) to clarify this discrepancy. The patients had chronic constipation (81), neurogenic faecal incontinence (31), rectal mucosal prolapse (1 7) or female urinary stress incontinence (9). All underwent measuremen ts of PD (by perineometry), anal sphincter pressures, single fibre ana l sphincter electromyography and PNMTL. These variables, as well as ag e were analyzed for a linear relationship with PD by multiple regressi on analysis. Age was the only independent variable predicting PD at re st (T = -3.2; p < 0.005). PNMTL was the only independent variable pred icting PD on straining (T = -3.0; p < 0.005). In conclusion, a linear relationship between PD on straining and PNMTL was confirmed, supporti ng the previous study which also measured PD by perineometry The other study which refuted such a relationship measured PD radiologically, a nd it is likely that the difference was in the measurement technique.