Translumbosacral neuromodulation therapy (TNT) improves symptoms of fecal incontinence (FI), but its mechanism of action is unknown. We tested the hypothesis that TNT at one or more frequency will significantly improve underlying pathophysiology of FI through modulation of ascending and/or descending signaling pathways in the gut and brain axis and anorectal sensorimotor function.
We assessed afferent anorectal-cortical evoked potentials (CEP) following electrical stimulation of anorectum, efferent cortico-anorectal and lumbo-anorectal and sacro-anorectal motor evoked potentials (MEP) after transcranial and lumbosacral magnetic stimulations, and anorectal manometry before and after six weekly TNT sessions in FI subjects, randomized to 1, 5, or 15 Hz repetitive magnetic stimulations. Neurophysiology, anorectal sensorimotor function, and symptoms were compared to examine mechanistic effects. Co-primary measures were ano-cortical CEPs, cortico-anal MEPs, and lumbosacral-anal MEPs. Baseline and post-treatment data were compared with Wilcoxon signed-rank test and changes between the three frequencies with one-way ANOVA.
Thirty-three FI patients participated. After TNT, the afferent anal CEP latencies significantly decreased in the 1 Hz group compared to baseline (p = 0.0029) and 5 Hz or 15 Hz groups (p = 0.032). Cortico-anal MEPs were unchanged in all three groups. Bilateral lumbo-anal and sacro-anal MEP latencies significantly decreased with 1 Hz, lumbo-anal with 15 Hz, and sacro-anal with 5 Hz compared to baseline but without group differences. The 1 Hz group showed significant increase in anal squeeze sphincter pressure (p < 0.005) and maximum tolerable volume (p < 0.019) and demonstrated higher FI responder rate (p < 0.04) compared to the other two groups. The MEP responders were significantly correlated with FI responders (p = 0.006) in 1 Hz group.
TNT significantly improves afferent ano-cortical signaling, efferent lumbo-anal and sacro-anal neuropathy and anorectal sensorimotor function. These neurobiologic effects were most prominent with 1 Hz frequency. TNT improves FI by modifying the underlying pathophysiology possibly through neuromodulation.

© 2021 International Neuromodulation Society.