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LARS is a significant problem found in about one third of rectal cancer patients after colorectal anastomosis. Symptoms of concern include pain on defecation and decreased ability to hold. Risk of having major LARS increases with adjuvant treatment and lower anastomotic level.

Background/Aim Brain-gut dysfunction has been implicated in gastrointestinal disorders but a comprehensive test of brain-gut axis is lacking. We developed and tested a novel method for assessing both afferent anorectal-brain function using cortical evoked potentials (CEP), and efferent brain-anorectal function using motor evoked potentials (MEP). Methods CEP was assessed following electrical stimulations of anus and rectum with bipolar electrodes in 26 healthy subjects. Anorectal MEPs were recorded following transcranial magnetic stimulation (TMS) over paramedian motor cortices bilaterally. Anal and rectal latencies/amplitudes for CEP and MEP responses and thresholds for first sensation and pain (mA) were analyzed and compared. Reproducibility and interobserver agreement of responses were examined. Results Reproducible polyphasic rectal and anal CEPs were recorded in all subjects, without gender differences, and with negative correlation between BMI and CEP amplitude (r −0.66, p=0.001). TMS evoked triphasic rectal and anal MEPs, without gender differences. Reproducibility for CEP and MEP was excellent (CV <10%). The inter-rater CV for anal and rectal MEPs was excellent (ICC 97–99), although there was inter-subject variation. Conclusions Combined CEP and MEP studies offer a simple, inexpensive and valid method of examining bidirectional brain-anorectal axes. This comprehensive method could provide mechanistic insights into lower gut disorders.

Background Neurological dysfunction causes fecal incontinence, but current techniques for its assessment are limited and controversial. Objective To investigate spino-rectal and spino-anal motor evoked potentials simultaneously using lumbar and sacral magnetic stimulation in fecal incontinence and healthy subjects, and to compare motor evoked potentials and pudendal nerve terminal motor latency in fecal incontinence subjects. Design Prospective observational study. Settings Two Tertiary Care Centers. Patients Adult fecal incontinence and healthy subjects. Interventions Translumbar and transsacral magnetic stimulations performed bilaterally by applying a magnetic coil to the lumbar and sacral regions in 50 fecal incontinence (≥ 1 episode/week) and 20 healthy subjects. Both motor evoked potentials and pudendal nerve terminal motor latency were assessed in 30 fecal incontinence patients. Stimulation-induced motor evoked potentials were recorded simultaneously from rectum and anus with two pairs of bipolar ring electrodes. Main Outcome Measurements Latency and amplitude of motor evoked potentials after lumbosacral magnetic stimulation and agreement with pudendal nerve terminal motor latency. Results When compared to controls, one or more lumbo-anal, lumbo-rectal, sacro-anal, or sacro-rectal motor evoked potentials were significantly prolonged (p<0.01) and were abnormal in 44/50 (88%) fecal incontinence subjects. Positive agreement between abnormal motor evoked potentials and pudendal nerve terminal motor latency was 63% whereas negative agreement was 13%. motor evoked potentials were abnormal in more (p <0.05) fecal incontinence patients than pudendal nerve terminal motor latency, 26/30 (87%) versus 19/30 (63%) respectively, and in 24% of patients with normal pudendal nerve terminal motor latency. No adverse events. Limitations Anal electromyography was not performed. Conclusions Translumbar and transsacral magnetic stimulation–induced motor evoked potentials provide objective evidence for rectal or anal neuropathy in fecal incontinence patients and could be useful. Test was superior to pudendal nerve terminal motor latency and appears to be safe and well tolerated.