Special Circumstances

Upper airway stimulation (UAS) has emerged as a viable alternative to treat obstructive sleep apnea in select patients who cannot tolerate continuous positive airway pressure. This chapter discusses special populations and circumstances that may impact care of patients using UAS. Topics addressed include women receiving implants, patients with Down syndrome, left-sided implants, replacement of an internal pulse generator, revision surgery, use of UAS with other implanted medical devices, and implants outside of indications approved by the U.S. Food and Drug Administration. Evidence is provided where applicable, but for many of the situations detailed, limited published data are available; the information provided represents consensus and expert opinion.

Painful Diabetic Neuropathy

Diabetic neuropathy may cause numbness and burning pain in a distal, symmetric distribution, typically involving the hands and feet. Management is with improved glucose control and treatment with tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors, and anti-epileptics. Surgical treatment is reserved for those patients with severe symptoms, with significantly impaired quality of life, for whom medications have not provided significant relief. There is evidence that spinal cord stimulation can provide a significant reduction in pain. A temporary trial of stimulation should be performed prior to permanent implantation. Leads may be placed in the epidural space percutaneously or via laminectomy and are connected to an internal pulse generator. Complications are typically device related. Treatment of device infection may require device removal.

Trigeminal Neuropathic Pain

Trigeminal neuropathic pain (TNP) involves pain isolated to the distribution of one or more branches of the trigeminal nerve following unintentional injury to that nerve. It is important to distinguish this facial pain syndrome from trigeminal neuralgia, as the treatment is quite different. The diagnosis is typically clinical, although local anesthetic blocks may aid in the diagnosis. Psychological testing is often performed preoperatively. Like other neuropathic pain syndromes, TNP may be treated with peripheral nerve stimulation. This chapter discusses a typical presentation of TNP, as well as the evaluation and management process, including placement of subcutaneous electrodes and connection to an internal pulse generator.

Significant cephalad lead migration with use of externally powered spinal cord stimulator

Spinal cord stimulation has been an effective therapy for treatment of chronic low back pain over the last four decades. Over the years, there have been significant technological advances in the neuromodulation devices. Externally powered neuromodulation devices, that do not require an internal pulse generator (IPG) implantation, have recently been approved for treatment of chronic pain and the data on potential pitfalls and unforeseen complications with these devices is minimal. Here, we report a case of a 60-year-old woman with chronic back pain who underwent the implantation of one of such devices and developed complication that required neurosurgical intervention. The epidural stimulator leads in the patient migrated cranially to the T2 level that required extensive neurosurgical exploration. We believe this is the first reported case of such significant cranial epidural lead migration with the use of neurostimulation devices and demands more research into the safety of externally powered neurostimulation devices.

A Novel Approach for Responsive Neural Stimulator Implantation With Infraclavicular Placement of the Internal Pulse Generator

INTRODUCTION The Responsive Neurostimulation System (RNS, Neuropace, Mountain View, California) has been proven to be effective at reducing seizures in patients with partial-onset epilepsy. The system incorporates a skull-mounted neurostimulator that requires a cranial incision for replacement. Although integral to the functioning of the system, in some circumstances, such as in the setting of infection, this can be disadvantageous. At present, there are no alternatives to cranial implantation of the RNS System. METHODS We describe a novel procedure enabling implantation of the neurostimulator within the chest wall, using components from a peripheral nerve stimulator. In a patient who achieved complete seizure freedom with the use of the RNS System, distant site implantation provided a viable means of continuing therapy in a setting where device explantation would have otherwise been inevitable as a result of cranial infection. We present continuous electrocorticographic data recorded from the device documenting the performance of the system with the subclavicular neurostimulator. RESULTS Band pass detection rates increased by 50%, while line length detection rates decreased by 50%. The number of detections decreased from 1046 to 846, with a resultant decrease in stimulations. Although there was some compromise of function due to the elevated noise floor, more than 2 yr following the procedure the patient remains free of seizures and infection. CONCLUSION The salvage procedure we describe offered an alternative therapeutic option in a patient with a complicated cranial wound issue, using heterogeneous components with marginal compromises in device functionality and no sacrifice in patient outcome.

3-Tesla MRI in patients with fully implanted deep brain stimulation devices: a preliminary study in 10 patients

OBJECTIVEThe aim of this study was to evaluate the safety of 3-T MRI in patients with implanted deep brain stimulation (DBS) systems.METHODSThis study was performed in 2 phases. In an initial phantom study, a Lucite phantom filled with tissue-mimicking gel was assembled. The system was equipped with a single DBS electrode connected to an internal pulse generator. The tip of the electrode was coupled to a fiber optic thermometer with a temperature resolution of 0.1°C. Both anatomical (T1- and T2-weighted) and functional MRI sequences were tested. A temperature change within 2°C from baseline was considered safe. After findings from the phantom study suggested safety, 10 patients with implanted DBS systems targeting various brain areas provided informed consent and underwent 3-T MRI using the same imaging sequences. Detailed neurological evaluations and internal pulse generator interrogations were performed before and after imaging.RESULTSDuring phantom testing, the maximum temperature increase was registered using the T2-weighted sequence. The maximal temperature changes at the tip of the DBS electrode were < 1°C for all sequences tested. In all patients, adequate images were obtained with structural imaging, although a significant artifact from lead connectors interfered with functional imaging quality. No heating, warmth, or adverse neurological effects were observed.CONCLUSIONSTo the authors' knowledge, this was the first study to assess the clinical safety of 3-T MRI in patients with a fully implanted DBS system (electrodes, extensions, and pulse generator). It provided preliminary data that will allow further examination and assessment of the safety of 3-T imaging studies in patients with implanted DBS systems. The authors cannot advocate widespread use of this type of imaging in patients with DBS implants until more safety data are obtained.