Pudendal nerve terminal motor latency: age effects and technical considerations

Objectives: The measurement of the pudendal nerve terminal motor latency (PNTML) is used to assess anal sphincter innervation. In healthy subjects, we studied the influence of age on PNTML and the advantage of a new intra-rectal stimulator. Methods: PNTML was determined in a first series of 40 normal subjects, aged 21–75 years, using a standard St. Markʹs electrode, and in a second series of 20 normal subjects over 50 years, using a new intra-rectal monopolar stimulator that did not require finger insertion through the anal canal. Results: In the first series, PNTML ranged from 1.8 to 5.6 ms (mean±SD 2.94±0.8 ms) and correlated positively with the age of the subjects (P=0.01, Spearman test). In the second series, PNTML ranged from 2.2 to 5.4 ms (3.7±0.9 ms) and was similar to that of the subjects over 50 years of the first series (3.5±0.4 ms) (P=0.35, Mann–Whitney U test). Conclusions: This study showed significant effects of age on PNTML. This should encourage every examiner to establish age-stratified reference values of PNTML for older age groups. In addition, we showed the advantage of using a new type of intra-rectal stimulator to reduce the patientʹs discomfort by avoiding finger insertion to stimulate the pudendal nerve.