Abstract
Coccygeal pain is a difficult chronic pain problem with mixed response to various treatments. This is a report of a case of coccygeal pain that after failing various conservative and interventional procedures over five years was evaluated with a temporary peripheral sacral fascial lead followed by implantation of bilateral sacral paramedian leads for peripheral nerve field stimulation (PNFS). This resulted in marked pain control and resumption of full activity. The visual analog scale (VAS) pain score improved from eight pre-implant to one after implant and has remained at that level in follow-up. Peripheral nerve field stimulation has been reported for axial chronic back pain, post-laminectomy pain and sacroiliac joint pain either alone or in conjunction with epidural spinal cord stimulation. Both single and parallel leads have been used to provide wider stimulation but differences in location have not been examined. This is the first case report of the use of PNFS for treatment of intractable chronic coccygeal pain. The effectiveness of PNFS was established for this patient by using a prolonged 10-day temporary trial period followed by a 30-day interval without stimulation during which the pain returned to the pre-trial level before proceeding with permanent implantation, it was clear that in this case, PNFS was effective for pain control. Interestingly, the trial and permanent leads were both in the posterior sacral fascia but not in identical positions yet equally effective for pain control. The observation of the effectiveness of different positions may indicate that at least for peripheral field stimulation there may be significant current spread in the fascia. Two and three months after the implant, we examined the effect of different lead settings and the effect of unilateral stimulation compared with bilateral stimulation with and without interlead communication. The patient feedback in this case provides some understanding of the effect of field stimulation with different lead placements. A trial of a deep peripheral fascial lead for sacral and coccygeal field stimulation is a simple option and may be a reasonable approach to consider in the range of treatments for chronic coccygeal pain.
Highlights
Some authors have used ultrasound guidance to position the electrodes in the deep fascia but in this case all leads were placed under fluoroscopic guidance [4,7,8]
Several reports have tried to equate the use of peripheral transcutaneous neural stimulation (TNS) to an implanted subcutaneous electrode trial but results and predictability of the effectiveness for a permanent implant have not been consistently based on patient response to TNS [4,9]
Chronic coccygeal pain is a difficult problem to manage if more conservative treatments using physical therapy, medications or localized blocks fail
Summary
During the initial five-day trial, she continued with the same stimulation which provided coverage to the bilateral paramedian and lower sacrum and coccyx areas with marked pain relief Her VAS score went from pre-procedure of eight to zero to one, there was a total change in facial expression and she spontaneously stopped all pain medication. The original post-implant settings for the permanent implant were the following which provided excellent pain relief for the initial nine weeks: four electrodes on each side with the following settings of left lead +2 and +3 and -5 and -6 and the right lead +10 and +11 and -13 and -14 At these settings, the patient felt equal stimulation bilaterally in the sacral para-spinal region midway between the iliac crest and down to the coccyx.
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