Neuromodulation devices range from intracranial, neuraxial (spinal cord or dorsal root ganglion), and peripheral (sacral nerve) stimulators.

Sacral neuromodulation involves placement of a quadripolar tined lead that stimulates sacral nerve roots to treat conditions such as fecal incontinence, urinary retention, and chronic pain after conservative management fails.

The mechanism of sacral nerve stimulators (SNS) is thought to involve activation of afferent pathways.

34-yo G1P0 @ 38w5d in labor w/ a Hx of IBS c/b persistent rectal prolapse treated with an Axonics SNS. Neurostimulator sited below the iliac crest, lateral to the sacrum, with leads entering through the S3 foramina (Image 1). An uncomplicated CSE was placed at L4-L5 in midline position f/b PCEA (infusion 10 mL/hr of 0.0625% bupi-2 mcg/mL fent, demand dose of 5 mL Q 10 min). One 10 mL top off of 0.25% bupivacaine was administered during her labor. The patient delivered vaginally four hrs later & the epidural was removed without complications.

Pre-operative assessment of SNS should include device type, last interrogation, and confirmation of location with lumbosacral US, XR or fluoroscopy. SNS generally does not affect neuraxial block placement unlike neuraxial stimulators which are often in lumbar or thoracic levels (higher risk of lead infection & epidural fibrosis). If CD is indicated, bipolar cautery is favored, or grounding pad should be on the C/L side and far away. If emergent defibrillation is necessary, place pads far from the device and perpendicular. Pad external stimulators/batteries to prevent pressure injuries. Patients with neuromodulation devices should be referred to anesthesiology as part of delivery planning.