In general, there are two reasons to implant percutaneous electrode leads. One is to use them for a short-term testing of the modality (so-called stimulation trial) and another is to provide long-term stimulation (so-called permanent implantation). Although the trial and permanent electrodes are positioned in the epidural space in a similar fashion, these interventions have their distinct nuances and may require different electrode leads as most manufacturers supply “temporary” electrode leads that are not intended for long-term stimulation and are used exclusively for trialing. The main difference between trial and permanent implantation is that trial leads are usually inserted without any incision using a pure needle-based percutaneous approach, whereas permanent implantation of percutaneous electrodes included making surgical incision and anchoring the electrode leads to the deep tissues. It is not uncommon to use percutaneous electrode leads for trial only and then to proceed with permanent implantation of paddle-type surgical electrode leads. The advantages of pure percutaneous trial is its low invasiveness, option to perform electrode lead insertion in office setting (as long as there is sterile procedure room and proper radiological control, e.g., fluoroscopy device such as C-arm), simplicity of lead removal at the end of the trial period, and lack of any incision that would require surgical skills, hemostasis, ability to suture, etc. A shortcoming of a percutaneous trial is that if the trial was successful, the lead still has to be removed and discarded, and a subsequently implanted permanent lead may need to be positioned in exactly the same location through a separate procedure (and this may be quite challenging due to development of epidural adhesions ant therefore trial results may be less predictive of long-term outcome).

In our practice, the majority of implanted SCS devices include percutaneous electrode leads—and with the use of this lead type we prefer to avoid having the patient go through electrode insertion twice. Therefore, we use the so-called “tunneled trial” approach: the trial electrode leads are inserted as if they were permanent—with incision, anchoring, etc.—and then temporary extension cables are tunneled out and used for connection to an external pulse generator (EPG). If the trial is successful, the extension cables are discarded and the electrode leads that were used for trial are kept in place and get connected to an implantable pulse generator (IPG) placed through a separate incision. The main advantage of this approach is that the same electrode lead that was used during the trial will be utilized during the permanent phase of long-term treatment thereby matching the exact location (and effects) of trial electrode placement. From a technical point of view, the lead insertion becomes easier as the skin incision and tissue dissection with visual exposure of deep fascia make accessing the epidural space less complicated and more predictable. Since the procedure is more invasive, it is usually done in a standard operating room (which is an encumbrance for non-surgeons, but a much preferred location for surgeons) with easy access to surgical instruments, fluoroscopy equipment and hemostatic tools, as well as a routinely high standard of sterility. The disadvantage of the tunneled trial technique is that if the trial fails, the patient has to return to the operating room for lead/anchor/extension cable removal. In addition, for non-surgeons, the need in proper surgical technique may be a certain deterrent.

The initial steps in SCS procedure take place well in advance of the operative intervention. Proper patient selection, mandatory psychological evaluation, setting clear expectations of treatment, and detailed discussion of surgical intervention and its possible complications are key moments in the process of patient preparation for trial. The patient has to understand the concept of stimulation-induced paresthesias and be willing to participate in the trial lead insertion process as success in reaching anatomical location that produces concordant paresthesias is absolutely dependent on the patient’s feedback.

It is also important to document exact anatomical location of the patient’s painful areas as all of them have to be covered with non-painful paresthesias in order for SCS to be effective. Creation of so-called “pain maps” may be useful in estimation of eventual location of electrode contacts as most anatomic regions appear to have reliable correlates in terms of vertebral level of stimulation.

With this, it is important to obtain proper imaging of not only the level where the electrode will be inserted (usually, mid-lumbar or upper lumbar regions) but also the level where electrode contacts will be positioned as tight stenosis at lower thoracic levels or previous thoracic laminectomy may present significant challenge for optimal electrode lead placement.

We recommend discussing location of the generator implant with your patients beforehand—in general, our preference is to put them into the abdominal wall rather than buttock or flank area for the sake of easier recharge and programming, as well as for less discomfort during sitting and lying down. In addition, the abdominal IPG placement appears to result in less stress to the electrodes and/or extension cables thereby reducing the risk of migration or fracture [2]. The side of IPG implantation is dictated by patient’s individual anatomy, presence of surgical scars, shunts, stomas or external tubes, as well as by the patient’s driving status as those who drive may want to have the IPG on the left side of the abdomen so it does not interfere with the seatbelt position whereas for those spending more time in the passenger seat the opposite may be true.

The last concerns to be addressed prior to the lead insertion are the planned position of the active lead contacts, estimated number of leads (1–4) and contacts per lead (4–16), and the type of electrode lead to be used (manufacturer and model), including the number of contacts, length of the lead and the need in anchors and extension cables as this information has to be communicated with the vendor who will have requested devices available along with the mandatory backup devices in case of intraoperative technical challenges.