The epidural fibrous sheath: a guide for the replacement of a spinal cord stimulation electrode

During spinal cord stimulation there is sometimes a need to replace defective leads. Percutaneous lead replacement by recannulating the epidural space and "steering" the new lead to the prior location is sometimes very difficult, resulting in diminished analgesia. Since fibrous deposits are known to form around epidural catheters and epidural obstructions have been noted with other techniques, we have inserted the new lead through the well-dissected opening in the interspinal ligament. We will report the results of our case series.

In 11 patients with lead malfunction we reinserted a new electrode into the epidural space by first withdrawing the lead with one hand and inserting the new one through the interspinal ligament with the other. In using this method, we found we could position the new electrode almost identically to the first. In only 3 patients did we experience difficulty in identifying the opening for the insertion. In the successfully cannulated patients identical stimulation parameters and paresthesia areas were obtained. By experimentally injecting contrast dye through an epidural catheter inserted into the interspinal opening and epidural pathway, we could visualize a thin dense line representing the fibrous sheath.

Foreign bodies in the epidural space lead to fibrous deposits. Spinal cord stimulation, when those deposits form a sheath, the sheath is useful for lead revision. The procedure, if meticulously performed, has a high success rate.