The science behind programming algorithms for sacral neuromodulation.

Aim: Sacral neuromodulation (SNM) is a widely adopted treatment for overactive bladder, non-obstructive urinary retention and faecal incontinence. In the majority, it provides sustained clinical benefit. However, it is recognized that, even for these patients, stimulation parameters (such as amplitude, electrode configuration, frequency and pulse width) may vary at both initial device programming and at reprogramming, the latter often being required to optimize effectiveness. Although some recommendations exist for SNM programming, the scientific data to support them are understood by few clinicians.

Methods: This is a narrative review of the literature covering some of the science behind stimulating a mixed peripheral nerve and available preclinical data in the field of SNM. It covers electrode configuration, amplitude, frequency, pulse width and cycling considerations. The review is targeted at clinicians with an interest in the field and does not seek to provide exhaustive detail on basic neuroscience.

Results And Conclusions: Knowledge of the science of neuromodulation provides some guiding principles for programming but these are broad. These principles are not refuted by preclinical data but specific parameters in clinical use are not strongly supported by animal data, even after the limitations of small and large animal models are considered. The review presents a shortlist of programming principles on a theoretical basis but acknowledges that current practice is as much derived from evolved experience as science.