Sacral Nerve Stimulation (SNS)

Dr. Jothi Murugesan MBBS, MS, FRACS

General & Colorectal Surgeon (Laparoscopic & Robotic Surgery)

Bladder and bowel control problems are common and affect millions of Australians. Sacral Nerve Stimulation (SNS) is a gold standard treatment for patients with faecal incontinence. Where successful, the treatment can make substantial and sustained improvements in their quality of life.

How does a normal bowel work?

Once the bowel has absorbed nutrients from food, the waste (faecal material and gas) travels to the rectum, where it is stored until it is time to evacuate. As the rectum and the upper portion of the anal canal are richly supplied with nerves, they help sense the fullness in the rectum, triggering a reflex to the brain, via the sacral nerves. When you need to open your bowels (i.e. in a toilet, at a convenient time), the brain communicates with the anal sphincter muscles, via the sacral nerves, to relax, aiding evacuation.

What is SNM and how does it work?

If the brain and sacral nerves do not communicate well, the rectum is unable to function properly and this can result in bowel control problems. Sacral neuromodulation, by way of mild electrical pulses, targets this communication problem by stimulating the sacral nerves, which are responsible for communication between the bowel and brain.

What does SNM involve?

The treatment is low-risk, relatively minor and is usually performed as a day procedure at a hospital. The treatment involves two-stages, including a test phase and implant phase:

The Test Phase: To evaluate SNM as a treatment, the patient is placed in a prone position on an operating table and the area of the sacrum prepped and draped. Using fluoroscopic guidance, location of sacral nerve root S3 or S4, which control the bladder and bowel is located precisely. Following this, a thin temporary wire is inserted close to the sacral nerve roots S3 or S4 and then connected to a small external device which delivers stimulation to the above nerves. Once completed, the patient is discharged home and continues to record toilet habits during the test period in a bowel diary. Patients typically undertake a trial phase of 7-14 days. After this, the specialist will assess the patient’s initial response with the aim to achieve a minimum of >50% improvement in symptoms, including number of incontinence episodes before and after the test, patient satisfaction score and quality of life assessments. If successful, then the patient moves onto the implant phase.

The Implant Phase: involves the insertion of the sacral nerve stimulator through a small incision, below the bikini line, after a successful test phase. A thin lead is implanted in the lower back and is then connected to a battery. If the evaluation is unsuccessful, the temporary wire can be removed in clinic and we can consider either repeating the test or discussing other viable treatment options with the patient.

Unlike other treatments, SNM allows patients the opportunity to trial its efficacy on symptoms before proceeding to implant. At any time, during the test phase or after implantation, SNM is reversible, quick and simple.

How long does the treatment effect last?

Unlike other treatments options, SNM provides ongoing symptom relief for about 5 years before the battery needs replacing, which is a simple day procedure.

Key take home points

Effective treatment for:

• Faecal incontinence
• Urinary incontinence

Key advantages:

• Trial (test) period
• Can improve quality of life
• Adjustable
• Reversible
• Rechargeable

Further reading

1. Leng WW, Chancellor MB. How sacral nerve stimulation neuromodulation works. Urol Clin North Am. 2005;32:11-18.
2. Hull T, Giese C, Wexner SD, Mellgren A, Devroede G, et al. Long-term durability of sacral nerve stimulation therapy for chronic fecal incontinence. Dis Colon Rectum. 2013;56:234–245.
3. Patton V, Wiklendt L, Arkwright JW, Lubowski DZ, Dinning PG. The effect of sacral nerve stimulation on distal colonic motility in patients with fecal incontinence. Br J Surg. 2013;100:959–968.