Dr Thomas E Smith MBBS(Hons) MD FRCA FFPMRCA
What is a trial of spinal cord stimulation?
A trial of spinal cord stimulation involves inserting the spinal cord stimulation leads, but not the the IPG (battery device). An external pulse generator (worn on a belt) is used for 7 to 14 days to see how a person responds to spinal cord stimulation. Different patterns of stimulation may be tried in this time. If the person finds they experience great reduction in pain as well as other benefits (like better sleep), a trial is positive. The person can move to having a permanent implant with an IPG.
If the person doesn’t not get much reduction in pain, the trial is negative. The trial leads are removed.
What is the difference between a percutaneous trial and a tunnelled trial?
Tunnelled trial : An incision is made in the back and the leads are implanted and anchored deeply Then lead extensions are added that are “tunnelled” to emerge from the skin some distance away from the incision.
Advantage of a tunnelled trial: If the trial is positive, the person proceeds directly to a full implant with the IPG added to the existing leads. (The extensions were exposed to the outside and will be contaminated so they are removed.)
Disadvantages of a tunnelled trial: 1.Back wound pain from incision – this may interfere with assessing if SCS is helpful for chronic back pain. 2. Risk of deep infection is higher than with a percutaneous trial. 3. Risk of bleeding is higher with a tunnelled trial. 4. If the trial is negative (unsuccessful) the person has to have another theatre procedure to remove the leads – this means he or she will have had two incisions and the associated risks of infection, bleeding and scarring without any benefit from SCS.
Percutaneous trial: the trial leads are sited through the skin without any incision.
Advantages of a percutaneous trial: 1.Avoids back would pain. 2.Lower risk of deep infection 3.Lower risk of bleeding. 4. If trial is negative (unsuccessful), the leads can be simply pulled out in an outpatient clinic).
Disadvantage of percutaneous trial : If the trial is positive, the existing trial leads need to be removed in outpatient clinic and the person needs to be booked for “full implant” in which new leads and an IPG will be implanted.