Robert Evans, MD, ICA Medical Advisory Board member, answers frequently asked questions about InterStim.

Will InterStim help with the pain of IC?
With InterStim, you are really affecting the nerves that cause increased urinary frequency. You should not expect that it will have an effect on your pain. Further research is needed to assess this device's effects on the pain of IC.

Will I get immediate relief of my symptoms?
Some patients may experience immediate relief. Others may require reprogramming of the permanent implant, up to several times, in order to achieve optimal results.

How long can the test stimulator be left in place?
It can be left in place for about a week. After that length of time, the wires move themselves out, the tape tends to peel off, and effectiveness is lost.

Will my insurance cover InterStim?
Medtronic has been very helpful in getting the stimulators pre-approved. My policy is that we do not do a test stimulation until we get approval to test and pre-approval to use the permanent implant. We are very close to having a Medicare ruling on a code for the implant. Once this happens, the other insurance carriers tend to adopt the same procedure.

What kinds of physical activity can you do after InterStim implantation?
For the first week or so, the patient needs to keep the area dry. After about 3 weeks, when the incision is fully healed, there is no limitation of activity.

How long does the InterStim battery last?
Right now it is felt that the neuromodulator should work for seven to ten years. They make a nearly identical pulse generator for pacemakers. When the battery needs to be replaced, your physician can make a small incision and put a new battery in. This procedure takes approximately 15-20 minutes.

Is InterStim implanted under general anesthesia?
Yes. The permanent device is implanted under general anesthesia. However, for the test implant, the patient has to be awake so that they can let their doctor know if their bladder symptoms are responding to the test stimulator.

To date, there have been no reports of permanent nerve injury occurring with the use of InterStim. Due to lead migration, pain, and infection, there may be a need for reoperation (of the permanent implant) 15 to 30 percent of the time.

As with any surgical procedure, there are risks involved. Risks associated with this implant include infection, lead/wire migration that could necessitate a revision procedure, and post-operative pain in the area of the implant. Adverse events related to the therapy, device, or procedure can include:

• Pain at the implant sites
• Lead migration which necessitates additional surgery to reposition the leads
• Infection or skin irritation
• Technical or device problems
• Transient electric shock
• Adverse change in bowel or voiding function
• Numbness
• Nerve injury
• Seroma (cyst-like structure filled with fluid) at the neurostimulator site
• Change in menstrual cycle
• Undesirable stimulation or sensations.

InterStim is not intended for patients with mechanical obstructions such as benign prostatic hypertrophy, cancer, or urethral strictures. InterStim has not been studied in pregnant patients, children, patients with diabetes, or patients with multiple sclerosis. Patients are contraindicated for the implant if they have not demonstrated an appropriate response to test stimulation or are unable to operate the neurostimulator. Also, diathermy (e.g., short wave diathermy, microwave diathermy or therapeutic ultrasound diathermy) is contraindicated because diathermy's energy can be transferred through the implanted system (or any of the separate implanted components), which can cause tissue damage and can result in severe injury or death.