What is interstim?
Sacral neuromodulation is a minimally invasive treatment for patients who have an overactive bladder, or who cannot empty their bladder completely. It involves gentle electrical stimulation of the bladder nerves, which prevents the uncomfortable feeling of needing to urinate all the time, as well as preventing leakage when you do get that urge. It is effective in about 70% of patients who have failed more conservative options for their bladder problems. It is a very safe procedure, having been performed by urologists for more than 20 years. The other nice aspect of this procedure is that the device can be removed or revised at any time, if necessary.
How is it done?
Sacral neuromodulation is performed with you laying on your stomach. An anesthesiologist will administer some sedation, which is medication through an IV that makes you feel sleepy. It is the same type of anesthesia used for colonoscopy. Dr. Kumar then places a thin implantable electrode in a natural opening in the sacrum where the bladder nerves run after they exit the spine. She does this by piercing the skin with a very small needle (the size of one used to draw blood), and threading the wire through the bore of the needle and down into the correct space under X-ray guidance. Once she is satisfied with the placement of the wire, she will connect it to a small battery, the size of a silver dollar. The battery is then placed just under the skin in the upper buttock area, so you will not see it or feel it.
What does it feel like?
When the stimulator is turned on, you feel a tapping or vibratory sensation in the vaginal or labial area. You will have a controller to turn it up if you don’t feel it enough, or down if you feel it is too strong. It can be turned off at any time and you will always be able to contact a representative from the company if you have any questions about using the device. Within a few days, it should start improving your bladder issues.
Can I try it first?
In some patients, we will do an office test with a very thin wire, called a peripheral nerve evaluation. This allows us to test whether your nerves respond well to sacral neuromodulation, and it allows you to try the stimulation for 1-2 days. Using local anesthesia, Dr. Kumar will insert a very tiny wire (the size of a strand of hair), in the same fashion as the real neuromodulation wire. The wire is then taped to your skin and attached to an external battery. You will see Dr. Kumar in 48 hours so the temporary wire can be removed in the office and you can tell Dr. Kumar whether it improved your symptoms.
What are the risks of the procedure?
There are small risks for infection, and pain at the battery or lead site. Dr. Kumar is very aggressive about preventing infection by maintaining meticulous sterile technique at the time of insertion, which is why this procedure is done in a sterile operating room, even though it is minimally invasive and requires very little anesthesia. Occasionally, patients have pain at the site of the battery, especially if they have lost weight and the area has physically changed. If this happens, Dr. Kumar can simply change the position of the battery.
What can I expect after the procedure?
After the procedure you will have a prescription for antibiotics and pain medication. You will be shown how to use the patient controller, and you will be given contact information so you can call if you have any questions or issues at home. You will be shown how to use the patient controller, and you will be given the phone number to call if any issues. You will be instructed to limit any aggressive physical activity such as heavy lifting for about 6 weeks to allow the tissue to heal, but you can do regular walking, driving, and going up flights of stairs. You will follow up with Dr. Kumar for a wound check about 10-14 days after the procedure, and then again in about 6 months. If you are having any issues, you will come in sooner so these can be promptly addressed.
It is very important to recognize that you cannot have an MRI below the head if you have an Interstim device made by Medtronic, because there is metal in the battery and the lead. If you absolutely need an MRI, the device can be removed. For the Medtronic device, the battery life is about 5-7 years. In the future, sacral neuromodulation devices will likely be MRI safe, and come with rechargeable batteries.