AAMC Magazine

Summer 2000

Implantable Devices Offer Hope for Chronic Pain Patients

Two new procedures—implantable drug infusion therapy and spinal cord stimulation—may provide great relief and improve quality of life for patients who suffer from chronic pain. Both procedures are a collaborative effort of physiatrist Brian Kahan, D.O., neuroradiologist Timothy Eckel, M.S., M.D., and neurosurgeon Brian Sullivan, M.D.

Dr. Kahan said the types of patients who may benefit are those with spine ailments, multi-joint pain, trauma, failed back surgery, or regional pain syndrome. "It's an alternative to a life-time dependence on oral or injected pain medication—an alternative that can give you a better quality of life," he said. The procedures have been available in the past for patients with terminal cancer, but more recently, physicians have begun looking at them as an alternative to heavy medication. Both procedures require a trial period as well as a short hospital stay, he said, but the benefits can be worth the time.

Implantable Drug Infusion

In this procedure, the trial period consists of the delivery of a small amount of pain medication through an epidural catheter. The patient is monitored for several days. Dr. Eckel said, "The temporary catheter and trial period allow us to establish that the device will be useful in treating the patient's pain prior to permanent implantation. We also use the temporary trial to estimate effective medication dosages."

If pain is decreased by as much as 50 percent, surgery is scheduled to implant the infusion device, which is a small holding tank and pump about the size of a soup can lid. The device is surgically placed under the skin of the abdomen to deliver medication directly into the space around the spinal cord where fluid flows (the intrathecal space). Medication is delivered through a small tube, or catheter, that also is surgically placed. Because the medication goes directly to the spinal cord, where pain signals travel, patients should experience much less pain with a much lower dose of medication than would be required by oral medications (pills) or injections. Some dosages are reduced by as much as 300 percent. This helps minimize the side effects that often accompany other treatments.

The physicians monitor pain relief and adjust the pump to deliver the optimum amount of medication. About once every six weeks the holding tank must be refilled in Dr. Kahan's office. It is a relatively painless procedure that takes about 30 minutes.

Spinal Cord Stimulation

In this procedure, Dr. Eckel inserts a temporary electrode in the patient's spine on an outpatient hospital visit, and the patient goes home for a few days of a "trial run" with an external stimulator box. If the patient reports successful pain relief, a permanent electrode is implanted surgically. Patients should experience a 50-70 percent reduction in their pain and an increase in the ability to go about daily activities. Patients report feeling a tingling sensation when the impulses are delivered that block the pain.

For the permanent device, Dr. Sullivan implants a small neurostimulation system under the skin that sends mild electrical impulses to either the spinal cord or to a specific nerve. The electrical impulses are delivered through a lead, or wire, that also is surgically placed. The electrical impulses block the signal of pain from reaching the brain. Peripheral nerve stimulation works in the same way, but the lead is placed on the specific nerve that is causing pain.

Two methods are available for regulating the impulses. One system is internally powered and programmed externally by Dr. Kahan using radio waves. This procedure is done through the skin and is painless. Another system is powered externally, also using radio waves, and can be programmed by the patient. The physicians determine which device is best for which patient.

Evaluation and Treatment

Patients are referred to Dr. Kahan, who does an initial evaluation. Suitable candidates for either procedure are sent to Dr. Eckel, the neuroradiologist who simulates the therapy through the use of temporary devices. If the test phase is successful—that is, if the patient gets at least a 50 percent improvement in pain relief—then Dr. Sullivan will implant a device for long-term relief.

Dr. Sullivan said candidates for either procedure must have exhausted all other options before they will offer to perform the procedure. Other options include oral medication, behavioral management, physical therapy and biofeedback. "It's major surgery and not something we would perform on everyone who doesn't meet strictly inclusive criteria," he said. The risks associated with the procedures are the same risks associated with any major surgery. The procedures also involve a hospital stay and recovery period. In addition, the implantable devices must be replaced every seven years.

However, the advantages far outweigh the disadvantages. "Not only can pain be reduced significantly, many people can resume a functional lifestyle. It also can mean a vastly improved quality of life and the elimination of some of the side effects associated with large doses of medication," said Dr. Sullivan.

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