Konstantin V. Slavin MD University of Illinois at Chicago, Chicago, IL, USA, and Jesse Brown Veterans Administration Medical Center, Chicago, IL, USA Peripheral nerve stimulation (PNS) is an important part of the neuromodulation universe – this type of electrical stimulation has been successfully used for many important indications including chronic pain, epilepsy, depression, urinary incontinence, obstructive sleep apnea, gastroparesis, diaphragmal palsy, etc. [1]. Among all these PNS applications, its use in the treatment of head and face pain has probably been one of the oldest and therefore most established approaches. With the first reported use of trigeminal PNS in 1962 [2] and subsequent application of infraorbital PNS as the proof of concept for the “gate-control” theory of pain in 1965 [3], there is now a 60-year long experience with this modality. The technology of craniofacial PNS has advanced over the years making the implantation procedures less invasive and, to some extent, more uniform, but most importantly, making it available to pain specialists from non-surgical backgrounds, so the initial monopoly of neurosurgeons having a skill to implant electrodes in the vicinity of peripheral nerves is not there anymore and the majority of PNS devices are implanted by non-neurosurgeons. As a matter of fact, the most recent innovations and technologic breakthroughs resulted in significant miniaturization of PNS hardware, so the conventional pulse generators may now be replaced by “in-electrode” integrated circuits [4] or small, button-like receivers [5] powered by externally located generators. Nevertheless, the technology is far from perfect. Despite the high level of effectiveness and relative simplicity of use, there are multiple procedural and hardware-related issues that translate into complications and failures [6, 7], and it is important to be aware of this concern so the problems can be avoided or at least properly mitigated. The classification of neuromodulation complications has been described by us in the past [7]; seven out of 10 categories are applicable to the occipital and trigeminal nerve stimulation procedures (Table 54.1). Table 54.1 Categories of occipital and trigeminal nerve stimulation complications (adapted from [7]). 1) Infection 2) Hemorrhage 3) Injury of nervous tissue 4) Placing the device into the wrong location 5) Hardware migration 6) Hardware erosion 7) Hardware malfunction/fracture/disconnection. Some of these complications are related to the implantation process, some have to do with the long-term use of the implanted hardware, and, in all fairness, none of the complications are completely avoidable or preventable. Nevertheless, in attempt to reduce the incidence of complications, we will go through each category and list some of the approaches used to prevent them. It is important for each implanter to keep track of their complications, just as it is important to analyze one’s treatment outcomes, by doing so, the implanter may decide to modify his or her practice, add specific maneuvers aimed at making procedures safer, or even make an effort to avoid some devices that are associated with certain complication types. Applicable to occipital and trigeminal stimulation, for example, became our desire to avoid using any type of extension cables or high-profile anchors as they were noted to carry high risk of skin erosions. Here, we will group all complications into early, procedure-related (hemorrhage, nerve injury, wrong device location), and late, long-term treatment related (hardware erosion, hardware migration and hardware malfunction, including fractures and disconnections), and have a separate discussion of infections that are observed over both short- and long-term periods. Among procedural complications, hemorrhage arises from penetration of local blood vessels during insertion of the electrodes or tunneling these electrodes toward the generators. In our practice, electrodes for both trigeminal and occipital nerve stimulators are inserted using a percutaneous technique with fluoroscopic guidance [8, 9]; to minimize the risk of hemorrhage at the skin penetration/incision site, we routinely infiltrate the skin with a local anesthetic mixed with epinephrine before the skin is cut. Local vasoconstriction from epinephrine use tends to reduce bleeding. An advancement of the electrode insertion tool (a plastic introducer over the rigid stylet [10] or a specially bent Touhy-type needle [8]) is done with a steady movement in the subcutaneous plane. Doing it in such a way tends to push vessels aside rather than go through them. Similarly, avoidance of sharp insertion tools seems to decrease the possibility of vascular injury. We routinely use live fluoroscopy during the insertion process – this allows one to reach the target point with a single pass and eliminate multiple passes between the insertion point and the stimulation target. In the incisions needed for the anchoring, tunneling and generator implantation, we use the low-power bipolar coagulation to stop the bleeding, and irrigate the incisions with saline solution prior to the closure to confirm absence of hidden bleeding sources. Damage of the neural structures presents a major concern when neuromodulation is applied to the intracranial or intraspinal structures (the brain, spinal cord, ganglia and nerve roots). In peripheral nerve stimulation (PNS) procedures, this is less of an issue – but it is important to avoid both direct injury of the nerves during the insertion and tunneling process and the nerve compression by the device or the anchoring sutures. Knowledge of anatomy helps one to avoid injuring branches of the trigeminal or facial nerve when implanting electrodes in the patient’s face or hitting the accessory nerve or brachial plexus when tunneling the electrodes through the patient’s neck. In occipital nerve stimulation (ONS), use of ultrasound (US) may help in identifying the nerves and suggesting proper depth of electrode insertion. The use of blunt instruments, described earlier for prevention of vascular injury, may further minimize risk of direct nerve penetration as the nerve trunks are expected to move away from the advancing insertion tool. This refers to positioning of electrodes too deep or too superficial as each of the placement errors may result in its own set of complications. When electrodes are placed under the subcutaneous fascia, they end up in direct contact with the muscle tissue, and this may result in a well-described complication of development of muscle spasms in response to electrical stimulation [11]. When electrodes are placed too superficially, device erosion becomes rather inevitable (Figures 54.1 and 54.2).
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Complications of Occipital and Trigeminal Nerve Stimulation
Introduction
Indications
Contraindications
Complication Categories
Procedural Complications
Hemorrhage
Damage of the Nervous Tissue
Placing an Electrode in the Wrong Tissue Plane
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