Recommendations for anesthetic management for intraoperative neuromodulation cases

This paper performs a review of current literature as well as uses our single-center experience to discuss pre-operative, intra-operative and, briefly, postoperative management for dorsal column stimulators (DCSs), dorsal root ganglion (DRG) stimulators, peripheral nerve stimulators (PNSs) and intrathecal pumps. Generally, pre-operative antibiotics are recommended with discontinuation within 24 h postoperatively. For dorsal column and DRG stimulation, monitored anesthesia care or general anesthesia with intra-operative neuromonitoring is recommended; for peripheral nerve stimulation and intrathecal pump implementation, monitored anesthesia care is preferred. There is little information on appropriate anesthetic management during these forms of neuromodulation. More research is necessary to articulate specific pre-operative, intra-operative and postoperative management guidelines and recommendations for dorsal column stimulator, DRG stimulation, PNS and intrathecal pump implantation.

Neuromodulation in the Treatment of Painful Diabetic Neuropathy: A Review of Evidence for Spinal Cord Stimulation

Background: Neuropathies, the most common complication of diabetes, manifest in various forms, including entrapments, mononeuropathies or, most frequently, a distal symmetric polyneuropathy. Painful diabetic neuropathy (PDN) in the classic “stocking” distribution is a disease of increasing prevalence worldwide and a condition for which standard medical treatment only provides modest relief. Neuromodulation offers a potential alternative to pharmacotherapies given its demonstrated efficacy in other refractory chronic neuropathic pain syndromes. High-quality evidence from randomized controlled trials (RCTs) is available in these other settings for two approaches to spinal cord stimulation (SCS): (1) conventional low-frequency SCS (LF-SCS), which modulates axonal activity in the dorsal column and is paresthesia-dependent, and (2) high-frequency SCS delivered at 10 kilohertz (10 kHz SCS), which targets neurons in the superficial dorsal horn and is paresthesia-independent. Method: This review examines the evidence for SCS from published RCTs as well as prospective studies exploring the safety and effectiveness of treating PDN with neuromodulation. Results: Two RCTs enrolling 60 and 36 participants with PDN showed treatment with LF-SCS reduced daytime pain by 45% to 55% for up to two years. An RCT testing 10 kHz SCS versus conventional medical management (CMM) in 216 participants with PDN revealed 76% mean pain relief after six months of stimulation. None of the studies revealed unexpected safety issues in the use of neuromodulation in this patient population. Conclusion: These well-designed RCTs address the unmet need for improved PDN therapies and provide data on the safety, effectiveness, and durability of SCS therapy.

Evaluation of Pre-operational Factors Contributing to a Dorsal Column Stimulator Explantation

Objectives Implantation of a dorsal column stimulator (DCS) for axial spine and radicular pain is a commonly performed procedure. Despite the benefits of this device to reduce pain and improve quality of life, some patients elect to have the device explanted. The purpose of this study is to describe pre-operational factors among patients who elected to have their DCS explanted and how these factors are associated with reason for explantation. Materials and Methods We conducted a retrospective descriptive study using the database of a private outpatient orthopedic clinic. We included all patients who had a dorsal column stimulator explanted between January 1, 2007 and June 19, 2014. Data was collected on patient demographics, past medical and back surgery history, as well as details of implantation, permanent device implantation, and subsequent explantation. Reasons for explantation were categorized as: inadequate pain control using three categories (with no device-related pain/discomfort, with device-related pain/discomfort, or inadequate pain control and patient wants MRI), or pain resolved. Results A consecutive sample of 100 subjects who underwent explantation of a DCS was identified for review. Of these 100 subjects, 14 were excluded. Based on our data, we hypothesize that sex (57% female, 43% male) degenerative disc disease (72%), previous back surgery (70%), BMI classified as overweight (subject average = 28.3), history of tobacco usage (57%), and history of narcotic use (80%) may be potential risk factors for explantation. Conclusions With respect to clinical evaluation of patients as candidates for spinal cord stimulator implantation, we cannot recommend that any of the evaluated variables be considered a contraindication to proceeding with a trial procedure. Future studies are planned to compare these data to a control group of subjects to establish risk factors predisposing individuals to explantation of a DCS. Key words: DCS, neurostimulator, spine, pain, explantation

Afferent System Overview

The afferent, or sensory, systems include visual, auditory, somatosensory, and interoceptive (ie, pain, temperature, and visceral sensation) inputs to the central nervous system. This chapter briefly reviews principles of transduction, relay, and processing of sensory information. The dorsal column–medial lemniscal system is reviewed in more detail. However, pain, vision, olfaction, and hearing are reviewed in subsequent chapters. Sensory transduction refers to the transformation of a stimulus into an electric signal. This process involves several distinct families of cation channels and associated receptor types.

THE PLASTICITY OF NERVE FIBRES: THE PROLONGED EFFECTS OF POLARIZATION OF AFFERENT FIBRES

The review surveys various aspects of the plasticity of nerve fibres, in particular the prolonged increase in their excitability evoked by polarization, focusing on a long-lasting increase in the excitability of myelinated afferent fibres traversing the dorsal columns of the spinal cord. We review the evidence that increased axonal excitability (i) follows epidurally applied direct current as well as relatively short (5 or 10 ms) current pulses and synaptically evoked intrinsic field potentials; (ii) critically depends on the polarization of branching regions of afferent fibres at the sites where they bifurcate and give off axon collaterals entering the spinal grey matter in conjunction with actions of extrasynaptic GABAA membrane receptors; and (iii) shares the feature of being activity-independent with the short-lasting effects of polarization of peripheral nerve fibres. A comparison between the polarization evoked sustained increase in the excitability of dorsal column fibres and spinal motoneurons (plateau potentials) indicates the possibility that they are mediated by partly similar membrane channels (including non-inactivating type L Cav++ 1.3 but not Na+ channels) and partly different mechanisms. We finally consider under which conditions trans-spinally applied DC (tsDCS) might reproduce the effects of epidural polarization on dorsal column fibres and the possible advantages of increased excitability of afferent fibres for the rehabilitation of motor and sensory functions after spinal cord injuries.

Thermosensitive collagen/fibrinogen gels loaded with decorin suppress lesion site cavitation and promote functional recovery after spinal cord injury

The treatment of spinal cord injury (SCI) is a complex challenge in regenerative medicine, complicated by the low intrinsic capacity of CNS neurons to regenerate their axons and the heterogeneity in size, shape and extent of human injuries. For example, some contusion injuries do not compromise the dura mater and in such cases implantation of preformed scaffolds or drug delivery systems may cause further damage. Injectable in situ thermosensitive scaffolds are therefore a less invasive alternative. In this study, we report the development of a novel, flowable, thermosensitive, injectable drug delivery system comprising bovine collagen (BC) and fibrinogen (FB) that forms a solid BC/FB gel (Gel) immediately upon exposure to physiological conditions and can be used to deliver reparative drugs, such as the naturally occurring anti-inflammatory, anti-scarring agent Decorin, into adult rat spinal cord lesion sites. In dorsal column lesions of adult rats treated with the Gel + Decorin, cavitation was completely suppressed and instead lesion sites became filled with injury-responsive cells and extracellular matrix materials, including collagen and laminin. Decorin increased the intrinsic potential of dorsal root ganglion neurons (DRGN) by increasing their expression of regeneration associated genes (RAGs), enhanced local axon regeneration/sprouting, as evidenced both histologically and by improved electrophysiological, locomotor and sensory function recovery. These results suggest that this drug formulated, injectable hydrogel has the potential to be further studied and translated into the clinic.

Clinical Reasoning: Middle-aged Man With Progressive Gait Abnormalities

Progressive spastic paraplegia is the core symptom of hereditary spastic paraplegia (HSP), a group of monogenic disorder characterized pathologically by degeneration of the corticospinal tract and dorsal column and leading to irreversible neurologic deficits. However, acquired causes, such as structural, vascular, inflammatory, infectious, metabolic, toxic, neurodegenerative, and iatrogenic causes can also cause acquired spastic paraplegia. We describe a case of a middle-aged man presenting with progressive spastic paraplegia combined with ataxia and parkinsonism. No mutation of HSP genes was detected. After a comprehensive diagnostic work-up, hyperintensities in the bilateral basal ganglia, mesencephalon, pons, and cerebellum on T1-weighted images were found, which demonstrated hypointensity on susceptibility weighted imaging (SWI). Furthermore, an increased blood ammonia level and diffuse slow wave activity in electroencephalogram were detected. Combined with a 7-year history of hypertension and alcoholic liver cirrhosis and the history of Transjugular Intrahepatic Portosystemic Shunt (TIPS) operation two years prior to the symptom of spastic paraplegia, concurrent acquired hepatocerebral degeneration (AHD) and hepatic myelopathy (HM) was finally diagnosed. The current case provided a detailed diagnostic approach for progressive spastic paraplegias and an exhaustive differential diagnoses of basal ganglia deposits. The take-home message from this case was that acquired causes, especially curable causes should always be excluded first when dealing with patients with progressive spastic paraplegia.

High frequency dorsal column spinal cord stimulation for management of erythromelalgia

Erythromelalgia is a rare hereditary channelopathy affecting the Nav1.7 sodium channel. Patients afflicted with this condition suffer from pain in their hands and feet, with vasomotor changes including flushing and redness to the distal upper and lower extremities. Current treatment modalities for this condition include pharmacological therapies (neuropathic medications), behavioural interventions, lumbar epidural infusions with local anaesthetics and sympathetic nerve blocks. Despite these treatments, many patients may have refractory pain. In these situations, there may be a role for dorsal column spinal cord stimulation for management of their pain. Here, we present the case of a 21-year-old man with 9-year history of refractory erythromelalgia successfully treated with paresthesia-free dorsal column spinal cord stimulation.