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Medtronic InterStim — Sacral Neuromodulation

Medtronic InterStim is the original and still-dominant sacral neuromodulation (SNM) platform — an implantable pulse generator (IPG) connected to a tined lead placed in the S3 sacral foramen that delivers low-amplitude electrical stimulation to the sacral nerve roots. FDA-approved for urgency urinary incontinence, non-obstructive urinary retention, urgency-frequency, and fecal incontinence.

Device Family​

InterStim II​

  • Non-rechargeable IPG — the classic workhorse
  • 44 × 51 mm device
  • Battery life variable by stimulation parameters (typically 3–5 years)
  • Requires replacement when battery depletes

InterStim Micro​

  • Smallest SNM IPG available — 17 × 47 mm (~80% volume reduction vs InterStim II)
  • Rechargeable — 20 minutes weekly charging
  • 15-year expected device life
  • 3T full-body MR-conditional labeling (2020)

InterStim X​

  • Recharge-free IPG with extended battery life
  • Latest Medtronic SNM offering (2022+)
  • Designed to match the recharge-free ease of the Axonics F15 generation

Common Components Across the Family​

  • Tined lead (SureScan MRI-conditional lead) — quadripolar, self-anchoring
  • Clinician programmer and patient controller
  • Smart-patient-programmer app (contemporary variants)

Indications​

  • Urgency urinary incontinence (UUI) refractory to behavioral and pharmacologic therapy
  • Non-obstructive urinary retention (idiopathic or neurogenic)
  • Urgency-frequency syndromes
  • Fecal incontinence

Staged Implant​

The standard SNM trial → permanent workflow:

  1. Stage I (basic evaluation) — percutaneous nerve evaluation (PNE) with a percutaneous wire for 3–7 days, OR a full tined-lead implant connected to an external pulse generator for 2–4 weeks
  2. Patient records voiding diary
  3. ≥50% improvement → proceed to permanent IPG placement
  4. Stage II — permanent IPG placed in an upper-buttock pocket, connected to the tined lead

Complications​

  • Infection — 1–3%
  • Lead migration — 2–5%
  • Pain at IPG site
  • Undesirable stimulation (leg pain, vaginal/perineal parasthesia)
  • Need for revision — 10–30% of recipients over lifetime

See also: Axonics SNM System, Percutaneous & Office Tibial Neuromodulation, Altaviva (Medtronic ITNS).