Magnetic pudendal neurostimulation: a novel method for measuring pudendal nerve terminal motor latency

Objective: Magnetic stimulation (MS) activates the neuromuscular tissue. Th is effect was used to develop a novel technique for measuring the pudendal nerve terminal motor latency (PNTML) to the external anal sphincter (EAS) i n healthy volunteers and patients with fecal incontinence. Methods: The PNTML was studied in 42 healthy volunteers (mean age 44.3 year s 30 men, 12 women) and 18 patients with neurogenic Fecal incontinence (mea n age 42.8 years: 12 men, 6 women) using two techniques in each subject: th e conventional intrarectal glove-mounted and MS. In the MS technique. the p udendal nerve was stimulated by a magnetic stimulator and a magnetic coil f ixed to the perianal skin at the: base of the ischioreotal fossa. Stimulati on parameters were set at 70% of maximum intensity, i.e. 175 J/pulse and 30 Hz frequency. The response of EAS to MS was recorded by a surface electrod e applied to the perianal skin in the vicinity of the anal orifice. Results: In healthy subjects, the PNTML recorded by MS from the right side (mean 2.2 ms) showed no significant difference from the left PNTML (mean 2. 1 ms) and both values did not differ significantly from those recorded by t he intrarectal method (right 2.2 ms; left 2.1 ms). In incontinent patients, both the right and left PNTML measured by MS exhibited a significant incre ase compared to the normal (P < 0.05, P ( 0.05, respectively) but no signif icant difference if compared to values recorded by the intrarectal route. Conclusions: The results of measuring the PNTML to the EAS by MS were as ac curate as those measured by the intrarectal method. However, the MS method stems to be easier and more convenient to the patient. (C) 2001 Elsevier Sc ience Ireland Ltd. All rights reserved.