Sacral Neuromodulation electrically stimulates which nerves in the sacral spinal root?

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Sacral neuromodulation works by activating sensory input that travels through the sacral nerve roots to the spinal cord. The device delivers electrical pulses to the dorsal (sensory) fibers, modulating the afferent signals that regulate bladder and bowel reflexes. The fibers most relevant for this modulation are somatic afferents, which carry sensory information from the pelvic floor and perineal region via the sacral roots. By stimulating these somatic sensory pathways, the sacral spinal circuits controlling continence are adjusted, reducing overactivity and improving storage function.

Autonomic efferent would be motor output to smooth muscle or glands, which isn’t the primary targeted pathway here. Autonomic afferent would be visceral sensory signals from pelvic organs, but the therapeutic effect of SNM is attributed to modulating somatic sensory input that gates the sacral reflexes involved in continence. Somatic efferent is motor to skeletal muscles, not the pathway being stimulated for neuromodulation.