Spinal Cord Stimulator

How does it work?
This is a minimally invasive technique developed in the early 1970s which is very helpful for patients with intractable low back, arm and leg pain, chronic regional pain syndrome (also known as RSD) and interstitial cystitis. In general this modality is used when more conservative treatments have failed to produce any consistent and long-term relief. The number one indication in the US for these devices is the " failed back syndrome".

In general, spinal cord stimulation (SCS) is most indicated for painful conditions caused by various degrees of nerve damage. Initially it was believed that SCS works mostly through action on the dorsal columns of the spinal cord, however recent studies indicate that a vast array of neural mediators are also involved in the analgesic process.

In the initial trial phase, so-called screening epidural electrodes are placed through a needle in the epidural space, just behind the spinal cord. These electrodes are complex wires that are connected to an outside battery and, when turned on, generate a tingling sensation, overlapping the painful area. The trial period lasts several days or until a consensus is reached between the patient and the physician, whether this is successful or not. At least 50% reduction of pain is required for a trial to be considered successful. Thereafter, the trial electrodes are removed. At a later date the patient undergoes a surgical procedure, during which a new electrode lead and a power source called pulse generator are implanted. The latter is a small box that looks like a cardiac pacemaker. All these components are implanted under the skin and superficial tissues, so that nothing is visible on the body surface.

Controversies still exist among specialists whether to implant a single lead versus dual leads, four versus an eight-electrode system. Each patient should be individually assessed in order to match the best system for a specific condition. A psychological screening is usually required by the insurance company before each implantation.

There are two types of pulse generators:
1. A completely internal pulse generator containing a battery
2. An internal pulse generator supplied by external power source through a radiofrequency "antenna" applied to the skin.

The battery containing pulse generator is the preferred modality, since it is more convenient to use and it is easily adjusted. The disadvantage of this specific modality is that it requires battery changes every three to six years, based on the time the stimulator is used throughout the day. This is however a minimal surgical intervention under local anesthesia.

The implanted pulse generator can be turned on and off by the patient using a small telemetry device or a magnet. A separate external programmer allows for more complex internal pulse generator reprogramming by the physician. These adjustments may be necessary from time to time.

There is substantial scientific evidence on the efficacy of SCS for the treatment of patients with intractable nerve pain, failed back syndromes and chronic regional pain syndrome. Numerous studies have shown decreased pain intensity scores, functional improvement and decrease medication use with the use of SCS devices. It has been shown that certain patients with failed back syndrome respond better to SCS than re-operation.

General contraindications are: infections, drug abuse, severe psychiatric disease and coagulations abnormalities.

Patients should clearly understand all the risks, benefits and alternatives of this modality.

What to expect during the procedure
The patient is placed in a face down position. The appropriate area is prepped with an antiseptic solution and then a local anesthetic is used to numb the skin. A light sedative is usually administered, but the patient remains awake during the test stimulation. Under direct X-ray visualization the lead is introduced through a needle towards the target area. A mild, temporary discomfort may be perceived at this time.

If the trial stimulation is successful, the implantation will follow within a few weeks. This procedure is again carried out under mild sedation.

At least two small incisions are made in order to accommodate the implanted lead, pulse generator and the extension cable. The procedure can last between two to four hours and the patient can be discharged home the same day. The patient will be taught how to safely use the device at home and he or she will be able to use it immediately after the implantation takes place. Pain medication will be prescribed after the procedure due to expected mild postoperative discomfort.

The incision staples need to be removed two weeks after the implantation. During this interval the patient should avoid showers and should keep the incision covered in order to avoid any infections. Strenuous activities are to be avoided in the first few months after the procedure, so that scar tissue can form to further anchor the lead in place.