Effect of sacral neuromodulation on the spinal nociceptive reflex of patients with idiopathic overactive bladder.

Objectives.   Sacral root stimulation (SRS) is a technique to restore the idiopathic overactive bladder (IOB). However, its mechanism of action is yet to be elucidated. Hence, we studied whether SRS restored IOB through the mechanism of spinal neuromodulation. Materials and Methods.   Six IOB patients and 10 healthy volunteers were included in the study. The spinal nociceptive reflex was used as the index of spinal excitability and was evoked by electrical stimulation at the foot, with recording at the ipsilateral tibialis anterior. Results.   IOB patients had increased spinal excitability to somatic nociceptive stimuli of the lower limbs. This spinal excitability decreased and bladder function improved after SRS, an effect that outlasted actual stimulation by at least 30 min. Conclusions.   Our results showed that spinal excitability was increased in response to somatic nociceptive afferents in IOB patients. SRS restored bladder function, at least, in part, through spinal neuromodulation.