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Implanted Neurostimulators: Complications

From their early introduction in the 1970s and extending into the 1980s implanted neurostimulator devices were prone to some serious complications. The effective resolution of these allowed more of a focus on less serious problems. These typically involved hardware failure usually occurring 3-5 years following implantation. Initially the most frequent failure mode was the break-down of lead wire insulation producing a short-circuit and accompanying malfunction of the device.

Significant improvement in low profile and more durable lead wires and connectors have significantly reduced neurostimulator problems. The present most common failure mode in surgically implanted systems requiring surgical revision is in lead wire or component failure.

Shown to the right are two examples of lead wire fracture shown next to the red dots. The first is next to the implanted epidural plate electrode and the second is close to the subcutaneous RF receiver.

Electronic failure of Internal Pulse Generators (IPGs) or Radio-Frequency (RF) receivers is uncommon. Shown below is an example of a lead wire failure secondary to the entrance of biologic fluids into the sealed electrode producing a short- circuit.

The first efforts of the Department of Neuroaugmentive Surgery (NAS) at Sister Kenny Institute were directed to avoiding unnecessary complications and to improve reliability by decreasing component failure through better materials and designs. The single most important initial contribution at that time was was the development of the intradural stimulating electrode. The physicians of NAS were instrumental in setting up the neurosurgical criteria for patient screening as well as the establishment of the CPT coding for implanted electronic devices.

At this point in time one of the greatest failings in regard to the use of neurostimulating devices is poor patient selection. This is particularly true when patients are on significant amounts of opioid narcotics and, for this reason, are not producing endogenous opioids (endorphins).

With appropriate patient selection and screening and implantation being performed by well trained and experienced surgeons complications are few and when they occur are only an inconvenience rather than a disaster for the patient.