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

Anchoring a Trial Electrode

What is the impact of anchoring the screening electrode at the time of implantation for chronic use if the screening trial is successful?

Expense:  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 (see "Setting" below).  On the other hand, a percutaneous catheter electrode designed solely for screening can be less expensive than electrodes designed to be implanted.

Setting: Inserting a temporary, unanchored percutaneous catheter electrode for the screening trial simply requires sterile conditions and fluoroscopy.  In contrast, anchoring a screening trial electrode for potential permanent stimulation requires a surgical incision in an operating room, which increases expense and scheduling difficulty.  Should a trial fail, the unanchored percutaneous catheter electrode can be removed easily; removal of an internally anchored electrode must take place in an operating room.

Outcome: 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 captured during the screening trial.  Implanting a new, permanent electrode in a patient who has gained experience through the screening trial, however, might give the clinician the opportunity to improve upon the results of the screening trial.

Anchoring a trial electrode for potential permanent stimulation increases incisional pain (which could confound the interpretation of the trial's success) and requires the use of a percutaneous extension cable, which increases the risk of infection.

It is reasonable for a patient and clinician to anticipate that an implanted SCS system will provide successful therapy (why otherwise would they participate in the screening trial?); yet this expectation could obfuscate evidence to the contrary during the short-term length of the trial.  Expecting the screening trial electrode to become part of the chronic stimulation system could reinforce this positive expectation and, thus, could cause the patient to report a false positive trial result or the clinician to interpret questionable results in an unwarranted positive light.  This source of bias is easily avoided by adopting the practice of always removing the trial electrode.