Percutaneous Peripheral Neuromodulation Lead Insertion Using a Novel Stimulating Coudé Needle

To the Editor: The initial open approach to peripheral nerve stimulation was associated with significant morbidity, complications, and reports of low efficacy (1–4). Attempts to address these problems led to the development of a percutaneous approach using small cylindrical electrodes. The use of peripheral nerve stimulation in treating chronic neuropathic pain states has seen a resurgence since Weiner and Reed successfully implanted percutaneous occipital nerve stimulator electrodes in 1999 (5). This percutaneous technique of electrode insertion allows minimally invasive placement of stimulating electrodes and enables access to novel areas of stimulation, such as single nerves, previously the exclusive domain of surgery (6,7); the nerve plexus (8); subcutaneous targets/field (9–12); or the sympathetic chain (13,14). These advantages have led to an increase in its popularity, allowing treatment of chronic pain states either as a standalone treatment or in combination with spinal cord stimulation (15–18). A parallel development of short-term subcutaneous electrical nerve stimulation (percutaneous electrical nerve stimulation) as a percutaneous neuromodulation treatment also took place, making a useful addition to the existing permanent implantation techniques (19). Successful implantation of these percutaneous electrodes relies upon correct anatomical placement near the nerve or in the appropriate subcutaneous plane. The previous technique of insertion involved placement via an inert introducer needle, either blind or guided by imaging (9,20,21). As commonly used electrodes are 1.2-mm-diameter cylindrical spinal cord stimulator (SCS) leads, this required placement through an introducing needle of at least 14G (e.g., a modified Tuohy needle) or a 14G cannula (20,21). The stimulation patterns can be checked for correctness only after the electrodes are placed. If the stimulation is unsatisfactory, the procedure has to be restarted from the beginning with reinsertion of these large-diameter introducer needles. An alternative is to use a small-diameter nerve stimulator needle to locate the correct target, with placement of the introducer and electrode parallel to it. However, these regional-anesthesia nerve stimulator needles are too small to allow passage of a SCS electrode through them. Again, unsatisfactory stimulation will require the needle to be reinserted. These methods are both potentially time-consuming and inaccurate and risk tissue damage with multiple needle passes. Furthermore, incorrect placement results in inadequate pain relief due to poor coverage, and there is a risk of lead erosion or painful unwanted stimulation if the lead is too superficial. Abejon et al. (22) reported the importance of optimal depth of lead placement for target/field stimulation, hence reiterating the need for on-table testing. Initially we developed a simplified technique that allows determination of the correct place and depth of electrode placement using an introducing cannula that allows stimulation at its tip. This method is based on use of a modified stimulating 14G SCS TuohyPlexoLong needle (Pajunk GmbH, Gesingen, Germany). This stimulating needle offered an improvement on the existing techniques and was positively assessed during the trial (Fig. 1) (23). Subsequently we have selected existing Coudé needles for further modification, as in our view they offer better precision and flexibility, allowing the user to place the introducing needle at the correct site prior to electrode stimulation insertion. This minimizes multiple needle insertions and improves accuracy and precision in electrode placement (24).