Implanted spinal neurostimulators for the relief of pain are now big business. When such devices were first utilized in the 1970s by the neurosurgical community a number of important criteria were established for their use. These included:
Utilization was considered to be as a last-resort therapy To be considered only after chronic pain rehabilitation and applied only in patients not on significant narcotic drugs Most optimal for paleospinalthalamic pain management and initially most optimal for pain involving the lower extremities rather than the back.
As implanted spinal neurostimulators have become more commonplace many of the criteria established to promote a high degree of clinical success have fallen by the wayside. In addition to this non-surgeons, typically those involved in pain management and having no prior training in percutaneous procedures nor the use of fluoroscopy, have popularized spinal neurostimulators while paying little attention to the important patient screening criteria.
Because non-surgeons can only use needles for electrode placement the use of percutaneously placed epidural catheter electrodes (as opposed to surgically placed plate electrodes) has greatly increased. This is unfortunate because epidural catheter electrode systems tend to be unreliable due to their instability and tendency to migrate after placement. Other liabilities include a limited electrical field related to the small surface area of the electrodes. The most important value of catheter electrodes is in using them as a screening tool to determine patient candidacy for a definitive implantation.
Unfortunately, the problems of catheter electrode migration are further compounded by their utilization in patients on significant narcotic drugs. Typically percutaneous catheter electrodes are employed as part of a standard array of blocks, injections, etc. being directed to every patient entering procedure mills operated by feral procedurists preying on unsuspecting patients. The application of neurostimulation under these circumstances has not boded well for the continuing credibility of this important modality as a meaningful treatment in the future.
This illustration (courtesy of ANS) is important because it demonstrates the typical areas of stimulation parasthesia provided by a midline epidural electrode placed at the T8-10 level. Pain relief usually occurs in the anatomic area in which the patient feels the stimulation. Although the red area covers the low back and sacral area it is important to point out that neurostimulators in the past have been more effective in providing better pain relief to the lower extremities than to the midline body area. The area most resistant to pain relief by neurostimulation is the midline sacrum. With modern epidural plate electrodes the pattern of stimulation can be controlled to a reasonable degree by careful selection of active electrodes and by optimizing the output of the pulse generator.
When optimal patient selection is combined with careful screening on patients not impaired by heavy narcotics good long-term results are possible. Ideally patients use their neurostimulator for short periods of time to then experience pain relief, which can then last for hours,
The Editor’s experience has demonstrated that with careful patient selection, surgically implanted epidural plate electrodes, followed by ambulatory testing and pulse generator optimization, provide the best clinical results. Experience has also shown that the radio-frequency coupled systems are the most reliable, over time, and represent the most user-friendly devices for both patients as well as their physicians. It is also clear that the skill and experience of the surgeon have a great deal to do with a optimal result. Once again it is a matter of the carpenter and the nail.