Implantable Devices

Spinal Cord Stimulators and Pumps

Implantable devices, such a spinal cord stimulators and pumps which deliver narcotics and other medications to the spinal cord, are powerful tools to control pain which we have been unable to control by other means. Spinal cord stimulators are sometimes called dorsal column stimulators.

Spinal cord stimulators transmit very small electrical impulses to the spinal cord. These impulses can cause you to feel a pleasant sensation instead of pain.

1. Spinal Cord Stimulators

Stimulators are usually used in cases of neuropathic pain, such as occurs after back surgery or with Complex Regional Pain Syndrome, although there are other indications, such as inoperable heart disease and peripheral vascular disease, where it is also useful.

Before having a stimulator implanted, we perform a trial of the device to see if you like it. This trial is very easily performed. The spinal cord stimulator lead is placed into the epidural space very much like an epidural catheter is placed, using just a needle. There is no cutting involved. Trials are quick and easy to do; the only thing which would prolong a trial would be if it takes a long time to locate the precise spot where we want to stimulate you.

After the stimulator lead or leads are placed, they are secured, with the leads being attached to a programmer, which you can wear in a “fanny pack”. You will be given several different programs to use. You should spend the next several days using the different programs, finding out which you like the best.

We limit the length of the trial because we are concerned about the risk of infection if the leads are left in for too long.

After your trial is over, you will have your leads removed in our office. Lead removal is a quick, simple procedure.

If you find that during the trial, the spinal cord stimulator allowed you to function better, then we would proceed to a permanent implantation. Implantation involves placing the leads and anchoring them in your back, so that they do not move and placing a generator. We usually place a generator in the buttock, in the same area where a wallet would rest. Permanent placement is a surgical procedure; you may be uncomfortable from the procedure for up to 2 weeks after the procedure. You will, of course, be given both pain medication and antibiotics. In order to minimize the possibility of your leads moving from their optimal position, we will ask that you avoid activities that might move the leads, like reaching over your head or sitting up in bed: after lead placement, no overhead reaching. You must log roll out of bed.

Sometimes, instead of percutaneous leads inserted through a needle, we will use “paddle” leads, which are placed with a minilaminectomy by a spine surgeon.

Spinal cord stimulators are powerful, important tools in the treatment of pain; they are not perfect devices. Sometimes, we obtain perfect coverage during the trial but, despite stimulating the same area, we do not get good coverage during the permanent placement. This is a frustrating problem for which there is not always an easy answer. Treating chronic pain requires perseverance.

2. Pumps

Implantable pumps, which continually infuse medications, such as opioids or local anesthetics, provide an effective alternative to patients who are not tolerating their oral medications because of side effects or poor pain control.

The idea behind a pump is that the spinal cord is involved in sorting out all of the information which we get from the outside world, particularly with regards to such sensations as hot or cold, pressure or cutting. The function of this sorting out process is to present to the brain information which is important and not to present information which is not important, such as the fact that we have pressure on our feet while we walk.

As a part of processing all of this information, the spinal cord has receptors on it for multiple medications, such as narcotics. By selectively applying small amounts of narcotics (or other medications) to the spinal cord, it is possible to get the desired effect, such as pain relief, without the undesired side effects, such as nausea, vomiting or sedation.

To apply narcotics in this way, we generally use an implantable pump which has a reservoir to store the medication and a pump to regulate how fast it gets released from the reservoir. The pump is usually programmable, so that we can adjust the rate of the pump. The pump is attached to tubing which releases the medication into the cerebral spinal fluid, the fluid that surrounds, buffers and nourishes the spinal cord. Once in the CSF, the medication binds to the receptors on the spinal cord.

Prior to placing a pump, you are given a trial of medications. These trials can be inpatient or at home, done overnight or last several days. During the trial, we will usually give you just a narcotic, although we may occasionally add other medications.

If you have good relief of your pain with minimal side effects, then we can proceed with the permanent placement of a pump. This placement is a surgical procedure and involves making a pocket under the skin, usually in your abdomen, for the pump and then making a small incision in your back for the placement and tunneling of the subarachnoid catheter. You can expect to be sore for up to two weeks, just as you would after any surgery. You will be provided pain medication and antibiotics.

Pumps do require some maintenance. The reservoir does need to be refilled; we like to do so about every three months, but sometimes, it must be refilled sooner. Pumps can have problems. Although we follow a technique to minimize the incidence of catheter fracture, kinking or dislodgement, all of these things, and others, can occur. Accordingly, it may be necessary to repair the pump. Since we are refilling the pump, it is possible, even if unlikely, for an infection to occur, whether because of a refill or simply because the pump is there and presents a site for infection. Finally, the battery for the pump, like the battery for a stimulator, will not last forever and the device will need to be changed. Usually, the battery lasts about 5 years.

Pumps and stimulators are very powerful and very important parts of our treatment armamentarium. They allow us to treat problems which otherwise we would be unable to treat.