Practice Parameters for the Use of Spinal Cord Stimulation in the Treatment of Chronic Neuropathic Pain

Summary Procedure

Screening trial:

The three- to eight-day screening trial duplicates the definitive procedure and offers the most meaningful prognostic sign that SCS will succeed or fail.

A percutaneous catheter electrode placed under fluoroscopy provides easy access to multiple spinal levels and facilitates mapping of paresthesia/pain overlap to determine the optimal longitudinal level for the electrode.

A surgical plate/paddle electrode, however, might be required for screening if a percutaneous catheter electrode cannot access the epidural space satisfactorily, for example, in a patient who has undergone a previous laminectomy or posterior fusion at the level of insertion.   In addition, a surgical plate/paddle electrode might be useful to eliminate excessive side effects or provide sufficient pain/paresthesia overlap.

Anchoring an electrode for use during the screening trial and permanent stimulation thereafter reduces the cost of hardware in patients who have a successful trial but increases the cost of the screening procedure because it must be inserted and removed (if necessary) in an operating room.  Anchoring a trial electrode for potential permanent stimulation also increases incisional pain and requires use of a percutaneous extension cable, which increases the risk of infection.  On the other hand, a percutaneous catheter electrode designed solely for screening is relatively inexpensive, can be inserted under sterile conditions with a fluoroscopy, and can be removed easily.

Using the same electrode for the screening trial and permanent stimulation eliminates the possibility that the replacement electrode will not reproduce the pain/paresthesia overlap.  Using a new, permanent electrode, however, provides the opportunity to improve the screening-trial results.

Unless the trial electrode is routinely removed, a patient and clinician's bias that SCS will be successful could be bolstered by the expectation that the screening-trial electrode will becoming permanent and skew the results of the screening trial.

To control procedural pain during trial electrode placement, use a local anesthetic whenever possible.  An unconscious patient can not describe paresthesia coverage or react to changes in stimulation parameters or intraoperative events, which might increase the risk of neurologic injury.

The screening trial provides important information that will dictate the choice of electrode and stimulator to be implanted and the optimum stimulating configuration.

Medicare and many third-party payers require a successful screening trial before implantation.

A successful screening trial results in at least 50% patient-reported pain relief despite appropriate (provocative) physical activity, with stable or reduced analgesic consumption and patient satisfaction.  If sufficient pain/paresthesia overlap does not occur during the screening trial, a repeat trial should be considered.

Paresthesia coverage:

Stimulator parameters are adjusted by a trained professional during the screening trial and after implantation to 1) find the best settings for patients to use as they pursue activities of daily life, 2) maximize comfortable pain/paresthesia overlap, and 2) minimize power requirements.

Device options:

For screening trials, specially-designed, temporary (less costly) percutaneous electrodes are available, or either type of electrode designed for permanent use may be used with a temporary percutaneous extension cable.

The choice of electrode is determined by individual patient factors and individual clinical factors.  Percutaneous catheter electrodes have as many as eight contacts and can be implanted singly, creating a one-dimensional array or multiply, creating a two-dimensional array.  Surgical plate/paddle electrodes have as many as 16 contacts in one- or two-dimensional arrays.

The types of stimulator/power generators available are: 1) a radiofrequency receiver with no battery, requiring the patient to wear an external antenna and transmitter during stimulation; 2) a primary cell that requires surgical replacement when the battery is exhausted; and 3) a battery recharged by periodic use of an external radiofrequency transmitter.

The factors that dictate the choice of stimulator/power generator are: 1) the patient's ability to control the device, 2) the amount of power required, 3) patient convenience, and 4) patient cosmetic concerns.