Sacral Neuromodulation (Interstim)
Sacral neuromodulation, which is also called interstim, acts to provide a small amount of electrical stimulation to the nerves that run through the tailbone (sacrum) to the bladder. For reasons we do not well understand this can improve or eliminated bladder overactivity and urinary leakage from this. Another application of this therapy is for patients that develop urinary retention and cannot urinate effectively. This therapy can be thought of as a bladder pacemaker. The electrical stimulation is usually not something that causes pain or discomfort.
Who does this therapy work for?
One of the best applications of this therapy is for women that have overactive bladder. In this condition with aging the bladder starts to give inappropriate signals to urinate and patients feel urgency and frequency of urination. This is a condition that affects mostly aging women. When this condition is severe women will frequently have urinary leakage as a result of the bladder ‘spasms.” Another application of the therapy is in women that have a condition where their bladder stops working. This is referred to as Fowler’s syndrome. Often there is some precipitating factor like a recent unrelated surgery.
Other applications of sacral neuromodulation?
There are some other conditions that can respond to the use of sacral neuromodulation. One of these conditions is patients with partial spinal cord injury. Usually a good measure of partial spinal cord injury, which might respond to sacral neuromodulation is a patient with greater than 50% motor function below their injury. For instance some patients can walk after a partial spinal cord injury. These patients may respond to sacral neuromodulation and eliminated bladder spasticity or urinary retention. Another potential application is patients with multiple sclerosis that have good lower extremity function and can walk well. Similar to partial spinal cord injured patients the fact that these patients are ambulatory indicates that many of the spinal pathways that are needed for this therapy to work are intact.
How is sacral neuromodulation performed?
Sacral neuromodulation is an outpatient procedure that involves 2 operations about 1-2 weeks apart. In the first operation patients are in a twilight sleep with anesthetics and lie on their stomachs in the operating room. The locations of the nerves to the bladder are found and electrodes are placed onto the nerve on both sides. The electrodes are internally connected to temporary small wires that come out of the side of the body. When the patient wakes up a temporary stimulator is connected to these wires. The patient then has the nerves stimulated for 1-2 weeks from this external unit. If the patient’s urinary problem is improved by 50% or resolved with the therapy than the permanent unit is placed. In this second operation the permanent electrodes placed in the first operation are attached to a stimulator that is implanted above the buttock and hipbone. This unit will last 3-7 years depending upon several factors, like how much stimulation is required. It can be changed, in the future, when the battery wears out in a small surgery without disturbing the permanent electrode in the nerve. If the first surgery and the stimulation is not successful than in the second operation the electrodes are removed
Placement of percutaneous leads into the sacrum (tail bone) where the nerves travel to the bladder