Sacral Neuromodulation (SNM)

Urology

What is Sacral Neuromodulation (SNM)?

Sacral neuromodulation, or sacral nerve stimulation, is a surgical procedure for the treatment of overactive bladder (OAB) and non-obstructive urinary retention (NOUR).

It involves the placement of a small wire in the back, near the nerves that control your bladder. This wire is connected to a small pacemaker device (nerve stimulator) which delivers electric pulses to restore normal bladder function. The pacemaker device is a batterypowered electric pulse generator, and is placed underneath the skin of your back.

Who is suitable for SNM?

SNM is suitable for individuals who have not responded adequately or cannot tolerate dietary and lifestyle modifications as well as oral medications.

How is the procedure performed? There are two stages to SNM.

Stage 1: Test phase

This is usually done under anaesthesia at the Operating Theatre. A test wire is inserted through your back close to your sacral nerves and X-rays will be used to confirm its position. Once in the correct position, the wire will be secured and connected to the test stimulator which you will wear on a belt around your waist.

When the stimulator is turned on, you may experience a mild tapping, pulling, or tingling sensation in the genital (vagina/scrotum) or rectal (anus) area. It should never be painful. Over time, you will notice these sensations less as your body get used to the stimulation. You will need to monitor your bladder symptoms with a bladder diary before the next clinic review to decide if you are suitable for placement of the SNM nerve stimulator.

Stage

2: Placement of SNM

This is done under General Anaesthesia. The test stimulator will be changed to the actual SNM nerve stimulator placed at your lower back.

The alternative treatments for NOUR include:

• Intermittent self-catheterisation

• Long term urinary catheter

Post-procedure advice

• You may feel sore as well as some discomfort at the implant site. Avoid strenuous activities or stretching of your lower back as this can cause the wire to move out of position. It is important to keep dressings clean and dry

Source: Medtronic®

Are there any risks involved?

• Discomfort around the site of surgery

• Discomfort in the buttock, ankle/foot

• Infection which may require antibiotic treatment, possible device removal

• Need for replacement/relocation of device/wire

What are the alternatives?

The alternative treatments for OAB include:

• Intravesical Botulinum toxin (Botox®)

• Posterior Tibial Nerve Stimulation (PTNS)

• Augmentation Cystoplasty

• During the test phase, no showering or change of dressings is allowed to ensure the accuracy of the assessment

• We will monitor your progress and the device settings will be adjusted to maximise treatment effect as required.

• There may be unexpected triggering of airport security scanners due to the SNM device.

• Before undergoing any MRI (Magnetic Resonance Imaging), check if your SNM device is MRI-compatible

Figure 1. Sacral Neuromodulation (SNM) nerve stimulator

Long-term care for SNM:

• Sports and strenuous activities

Due to the risk of dislodging or damaging the SNM device or lead, avoid contact sports, extreme sports or activities that may potentially injure your back

• Surgical diathermy

Electrical current used during surgery to cut tissues can potentially damage the SNM device. Inform your surgeon about your SNM device and ensure that your device is switched off during surgery

• Security screening

Security screening and airport scanning devices can affect the SNM device. Show the security staff your SNM identification card and they may allow you to bypass the scanner. Alternatively, turn off your SNM device before passing through the scanner

• Battery failure (in nonrechargeable devices)

When the battery runs out, usually after 3-7 years depending on the settings used, the SNM stimulator will need to be changed via a simple procedure like the 2nd stage of the SNM insertion

When to seek medical attention:

• Adverse change in bowel function or urine function

• New pain, including at device site, leg, foot, lead site

• Significant skin irritation

• Lead migration

• Reduction in efficacy of the SNM when it was working well previously