Fig. 17.1
Example of regional peripheral stimulation (in this case for axial thoracic pain). The two sets of electrodes have been inserted subcutaneously along the length of the demarcated lateral borders of the patient’s painful region. Successful stimulation coverage for this patient was achieved via a combination of programs that used both the electrodes independently and in cross-talk configuration
For a stimulation trial, the electrodes may be stabilized by suturing them to the skin with a combination purse-string/drain suture. However, for a permanent stimulation system implantation, anchoring the electrodes is one of the more crucial steps, as electrode migration is one of the most frequently reported complications of these procedures. When anchoring the leads, it is important to identify a firm stable tissue layer to which to anchor the leads. In the cervical region this is often the most superficial layer of posterior cervical fascia. Anchoring to subcutaneous fat layers often leads to an unstable electrode that migrates with cervical motion. It should be noted that the anchoring depth is often deeper than the insertion depth. Given this, it is reasonable to first dissect down to the anchoring layer and then insert the needle and electrode more superficially during a permanent implant procedure.
Electrodes may be anchored with commercially available anchoring sleeves. If these are used, efforts should be made to avoid having the entire anchor located underneath the incision, so as to reduce the chance of erosion. The least bulky anchor possible should be utilized. Some physicians have chosen to forgo a formal anchor sleeve altogether and simply suture the lead to the fascia. It remains to be seen if this increases the chance of electrode fatigue and breakage over time. Subcutaneous pockets are may also be created around the main incision for placement of relaxing electrode loops to add slack to the system.
For permanent implantation, either percutaneous of paddle electrodes may be used. Percutaneous electrodes are now available in multiple configurations with anywhere from 4 to 16 stimulating contacts on the electrode. Electrodes with 16 contacts may enable the capture of bilateral greater occipital nerves with a single lead. To place a subcutaneous paddle lead a pocket for the body of the paddle must be created. This is typically done with gentle blunt dissection. It is important not to be overly aggressive and make this pocket much larger than the paddle body. Doing so not only can increase the diffusion of charge away from the target structure but also leads to more mobility of the electrode, which is suboptimal both in terms of comfort (patients feel the paddle rotating) and consistency of therapy.
When implanting upper cervical peripheral stimulating electrodes (those intended to treat syndromes such as cervicogenic headache and occipital neuralgia), several incision configurations may be used. If bilateral leads are to be tunneled to a generator implanted in the infraclavicular region, two incisions may be used: a submastoid incision ipsilateral to the generator and a midline incision (Fig. 17.2). For generators implanted in other dorsal locations, a single midline incision may be created with the electrodes both anchored in the same incision (Fig. 17.3).
Fig. 17.2
Percutaneously implanted upper cervical electrodes for stimulation of the occipital nerves. These were implanted via two separate incisions, one in the submastoid region and another in the midline
Fig. 17.3
Percutaneously implanted upper cervical electrodes for stimulation of the occipital nerves. These were implanted via a single midline incision. Note the relaxing loops present caudal to the electrodes
When performing peripheral stimulation procedures in the cervical region, there are several options for locating the implantable pulse generator (IPG) (Fig. 17.4). The leads may be tunneled laterally and over the clavicle to an IPG implanted in the upper chest. This provides for a short electrode distance (often without the need for extension wires) but may place torque on the leads with cervical motion, increasing the chance of lead migration if they are not securely anchored. The IPG may also be placed in the midline interscapular region. This allows for a shorter lead length with less force on the lead. If this location is considered, the patient should be observed sitting in chairs with backs of various heights to ensure that the IPG will not cause discomfort when the patient sits back against the chair. Another option is to place the IPG in the low back/upper buttock region. This will require the longest length of lead and often also requires the use of an extension wire down to the IPG site. For IPG implants in this location, attention must be paid to the total length of implanted lead/extension so that there is enough slack in the system to allow significant range of motion in both the cervical and lumbar regions without pulling the electrodes.
