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Spinal Neurostimulation Devices |
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 Courtesy ANS |
The successful "intradural" placement of stimulating electrodes
was the single key technical advance to demonstrate that spinal electrodes could be safely placed in stable
positions and did not have to reside in the subarachnoid space to be
effective. It then became apparent, from clinical experience, that the most
effective pain relief from spinal neurostimulators was primarily that involving the
lower extremities and, to a lesser degree, low back. |
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Because the largest manufacturer of neurostimulators was Medtronic,
Inc. they decided to focus on marketing internal pulse generators (IPGs).
By turning their back on the more compact and more reliable
radiofrequency coupled systems Medtronic allowed other companies the opportunity
of
further developing this attractive alternative.
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 Courtesy Medtronic |
In the illustration to the left a catheter electrode has been inserted through a percutaneously placed needle into the epidural space. This technique, which is done under local anesthesia with sedation, is attractive because it is relatively simple to perform. This ease of implantation has unfortunately made PENS electrodes the definitive implant for many physicians involved in pain management (who are not surgeons). PENS systems are notorious for their instability and tendency to migrate following implantation. | ||
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In the example shown above PENS electrodes have been placed for long-term stimulation (as a definitive implant). Over a two month period there has been electrode migration causing failure of the neurostimulator requiring revision. This is not an uncommon circumstance. In the author's practice PENS electrodes are used only temporarily for screening purposes and are removed after about a week. |
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This illustration shows PENS electrodes which have been connected to a IPG. As noted the early IPGs were typically associated with the need for multiple battery replacements and, because of this, multiple surgical revisions. Replacing IPGs may seem to be a simple procedure but, due to local scar tissue buildup, lead wires are not infrequently severed requiring replacement of the entire system. | ||
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Shown here is the surgical placement of a definitive plate electrode into the epidural space. This procedure is typically performed under general anesthesia. Unlike PENS electrodes epidural plate electrodes have a much higher degree of stability and much less failure. Experience has demonstrated that the greatest value of PENS electrodes is as a screening tool to determine if the patient is a good candidate for use of a neurostimulator for pain relief. | ||
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This illustration shows a radio-frequency (RF) coupled system where the batteries are in an external pulse generator. The RF receiver, which is about the size of a silver dollar, is placed under the skin and is activated by a small coil placed on the outside of the skin. Coil usually held in place with an adhesive pad. Anterior RF receiver placement is preferred so that the patient can properly align the transmitting external disc. | ||
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Other alternatives exist as means of holding the pad against the skin. Shown here is a tight fitting "fishnet" style T shirt under which the pad can be placed and held against the skin. | ||
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The Editor's experience, based on over 1,500 spinal cord neurostimulators implanted for the relief of intractable pain, has indicated that the combination of plate electrodes with RF coupled systems have been, until the present, the most user-friendly. They are also the most reliable as shown by their long-term success record. | ||
As with all medical devices and as with all surgeries there are potential complications. Fortunately, with neurostimulators the greatest risk is that of failure of the device itself, something which is usually replaceable. |
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Courtesy Medtronic
