Evidence-based consensus guidelines on patient selection and trial stimulation for spinal cord stimulation therapy for chronic non-cancer pain.

Spinal cord stimulation (SCS) has demonstrated effectiveness for neuropathic pain. Unfortunately, some patients report inadequate long-term pain relief. Patient selection is emphasized for this therapy; however, the prognostic capabilities and deployment strategies of existing selection techniques, including an SCS trial, have been questioned. After approval by the Board of Directors of the American Society of Regional Anesthesia and Pain Medicine, a steering committee was formed to develop evidence-based guidelines for patient selection and the role of an SCS trial. Representatives of professional organizations with clinical expertize were invited to participate as committee members. A comprehensive literature review was carried out by the steering committee, and the results organized into narrative reports, which were circulated to all the committee members. Individual statements and recommendations within each of seven sections were formulated by the steering committee and circulated to members for voting. We used a modified Delphi method wherein drafts were circulated to each member in a blinded fashion for voting. Comments were incorporated in the subsequent revisions, which were recirculated for voting to achieve consensus. Seven sections with a total of 39 recommendations were approved with 100% consensus from all the members. Sections included definitions and terminology of SCS trial; benefits of SCS trial; screening for psychosocial characteristics; patient perceptions on SCS therapy and the use of trial; other patient predictors of SCS therapy; conduct of SCS trials; and evaluation of SCS trials including minimum criteria for success. Recommendations included that SCS trial should be performed before a definitive SCS implant except in anginal pain (grade B). All patients must be screened with an objective validated instrument for psychosocial factors, and this must include depression (grade B). Despite some limitations, a trial helps patient selection and provides patients with an opportunity to experience the therapy. These recommendations are expected to guide practicing physicians and other stakeholders and should not be mistaken as practice standards. Physicians should continue to make their best judgment based on individual patient considerations and preferences.

Diagnosis and treatment of phrenic nerve hourglass constriction in patients with Parsonage-Turner syndrome.

Phrenic nerve injury can occur anywhere along its course and clinically results in diaphragm paralysis. Although most patients with Parsonage-Turner syndrome and phrenic nerve dysfunction improve without treatment, some patients do not recover spontaneously. In these cases, an initial autoimmune response produces scarring along the affected nerve(s). This scar, known as an hourglass constriction, causes focal compression of the nerve at the site of the scar, which prevents the nerve from spontaneously recovering. Thus, the authors present a unique case of phrenic nerve injury secondary to Parsonage-Turner syndrome that improved with internal neurolysis. The video can be found here: https://stream.cadmore.media/r10.3171/2022.10.FOCVID22105.

What's New in Peripheral Nerve Stimulation.

Peripheral nerve stimulation (PNS) is a powerful interventional option for the management of otherwise intractable pain. This technique involves the implantation of electrodes to apply electrical stimulation to named peripheral nerves, thereby alleviating pain in the territory of the target nerves. Recent advancements, largely driven by physician-industry relationships, have transformed the therapy into one that is minimally invasive, safe, evidence-based, and effective. Ongoing research has expanded the indications beyond chronic neuropathic pain in a peripheral nerve distribution. This article provides an overview of recent advances in this field.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guideline on Neuroablative Procedures for Patients With Cancer Pain.

BACKGROUND: Managing cancer pain once it is refractory to conventional treatment continues to challenge caregivers committed to serving those who are suffering from a malignancy. Although neuromodulation has a role in the treatment of cancer pain for some patients, these therapies may not be suitable for all patients. Therefore, neuroablative procedures, which were once a mainstay in treating intractable cancer pain, are again on the rise. This guideline serves as a systematic review of the literature of the outcomes following neuroablative procedures. OBJECTIVE: To establish clinical practice guidelines for the use of neuroablative procedures to treat patients with cancer pain. METHODS: A systematic review of neuroablative procedures used to treat patients with cancer pain from 1980 to April 2019 was performed using the United States National Library of Medicine PubMed database, EMBASE, and Cochrane CENTRAL. After inclusion criteria were established, full text articles that met the inclusion criteria were reviewed by 2 members of the task force and the quality of the evidence was graded. RESULTS: In total, 14 646 relevant abstracts were identified by the literature search, from which 189 met initial screening criteria. After full text review, 58 of the 189 articles were included and subdivided into 4 different clinical scenarios. These include unilateral somatic nociceptive/neuropathic body cancer pain, craniofacial cancer pain, midline subdiaphragmatic visceral cancer pain, and disseminated cancer pain. Class II and III evidence was available for these 4 clinical scenarios. Level III recommendations were developed for the use of neuroablative procedures to treat patients with cancer pain. CONCLUSION: Neuroablative procedures may be an option for treating patients with refractory cancer pain. Serious adverse events were reported in some studies, but were relatively uncommon. Improved imaging, refinements in technique and the availability of new lesioning modalities may minimize the risks of neuroablation even further.The full guidelines can be accessed at https://www.cns.org/guidelines/browse-guidelines-detail/guidelines-on-neuroablative-procedures-patients-wi.

Peripheral Nerve Stimulation for Facial Pain Using Conventional Devices: Indications and Results.

Trigeminal branch stimulation is a type of peripheral nerve stimulation (PNS) used to treat a variety of craniofacial pain disorders. Common indications include trigeminal neuralgia, trigeminal neuropathic pain, trigeminal deafferentation pain, trigeminal postherpetic neuralgia, supraorbital neuralgia, and migraine headaches. Supraorbital and infraorbital arrays are the most common electrode configurations, although preauricular, mandibular branch, and subcutaneous peripheral nerve field stimulation arrays have also been described. Trigeminal branch stimulation may be used as a stand-alone neuromodulation therapy or it may be combined with occipital nerve, sphenopalatine ganglion, or Gasserian ganglion stimulation to treat more complex pain patterns. Consistent with other forms of PNS, trigeminal branch stimulation is a minimally invasive, safe, and straightforward method of treating medically refractory neuropathic pain.

Evolving Techniques and Indications in Peripheral Nerve Stimulation for Pain.

Peripheral nerve stimulation is the direct electrical stimulation of named nerves outside the central neuraxis to alleviate pain in the distribution of the targeted peripheral nerve. These treatments have shown efficacy in treating a variety of neuropathic, musculoskeletal, and visceral refractory pain pathologies; although not first line, these therapies are an important part of the treatment repertoire for chronic pain. With careful patient selection and judicious choice of stimulation technique, excellent results can be achieved for a variety of pain etiologies and distributions. This article reviews current and past practices of peripheral nerve stimulation and upcoming advancements in the field.

Lateral Femoral Cutaneous Nerve Decompression Guided by Preoperative Ultrasound Mapping.

Injury to the lateral femoral cutaneous nerve (LFCN) from compression or entrapment may result in meralgia paresthetica, a painful mononeuropathy of the anterolateral thigh. Surgical decompression of the LFCN may provide relief when conservative management fails. However, the considerable anatomic variability of this nerve may complicate surgical localization and thus prolong operative time. Herein, we report the use of preoperative high-resolution ultrasonography to map the LFCN in a patient with bilateral meralgia paresthetica. This simple, noninvasive imaging technique was seen to be effective at providing precise localization of the entrapped and, in this case, bilateral anatomically variant nerves. Preoperative high-resolution ultrasound mapping of the LCFN can be used to facilitate precise operative localization in the treatment of bilateral meralgia paresthetica. This is especially useful in the setting of suspected unusual nerve anatomy.

ACR Appropriateness Criteria® Plexopathy.

MRI without and with contrast is the most accurate imaging method to determine whether a process is intrinsic or extrinsic to a nerve of the brachial or lumbosacral plexus. However, there are no Current Procedural Terminology codes to correspond to imaging studies of the brachial or lumbar plexus discretely. This assessment uses "MRI of the brachial plexus" or "MRI of the lumbosacral plexus" as independent entities given that imaging acquisition for the respective plexus differs in sequences and planes compared with those of a routine neck, chest, spine, or pelvic MRI, yet acknowledges the potential variability of ordering practices across institutions. In patients unable to undergo MRI, CT offers the next highest level of anatomic evaluation. In oncologic patients, PET/CT imaging can identify the extent of tumor involvement and be beneficial to differentiate radiation plexitis from tumor recurrence but provides limited resolution of the plexus itself. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diagnostic Biopsy of a Motor Branch of the Superficial Peroneal Nerve to the Peroneus Longus: A Convenient Alternative for Motor Nerve Biopsy.

BACKGROUND: Motor nerve biopsy is performed to supplement clinical, serologic, and imaging data in the workup of neuropathies of unknown origin, especially when motor neuron disease is suspected. METHODS: We describe a surgical technique for biopsy of a motor branch of the superficial peroneal nerve innervating the peroneus longus muscle. RESULTS: Three patients presented with weakness concerning for motor neuropathy and underwent biopsy of a motor branch of the superficial peroneal nerve innervating the peroneus longus muscle. The surgical technique is described in detail. Biopsied tissue was sufficient for pathologic diagnosis. No patient suffered postsurgical sensory or motor deficits related to the procedure. No patient suffered postsurgical complications. CONCLUSIONS: Biopsy of the motor branch of the superficial peroneal nerve to the peroneus longus is a safe and effective alternative for motor nerve biopsy and can be easily combined with peroneus longus muscle biopsy.

Trigeminal branch stimulation for the treatment of intractable craniofacial pain.

OBJECT Trigeminal branch stimulation has been used in the treatment of craniofacial pain syndromes. The risks and benefits of such an approach have not been clearly delineated in large studies, however. The authors report their experience in treating craniofacial pain with trigeminal branch stimulation and share the lessons they have learned after 93 consecutive electrode placements. METHODS A retrospective review of all patients who underwent trigeminal branch electrode placement by the senior author (C.J.W.) for the treatment of craniofacial pain was performed. RESULTS Thirty-five patients underwent implantation of a total of 93 trial and permanent electrodes between 2006 and 2013. Fifteen patients who experienced improved pain control after trial stimulation underwent implantation of permanent stimulators and were followed for an average of 15 months. At last follow-up 73% of patients had improvement in pain control, whereas only 27% of patients had no pain improvement. No serious complications were seen during the course of this study. CONCLUSIONS Trigeminal branch stimulation is a safe and effective treatment for a subset of patients with intractable craniofacial pain.

Schwannomas of the foot and ankle: a technical report.

The present technical report provides a detailed description of open surgical resection of peripheral nerve sheath tumors in the foot and ankle. We present 3 cases to illustrate important differences in the technique based on the presentation, anatomic location, and intraoperative neurophysiologic monitoring findings. It is important for surgeons to understand that surgical excision of many peripheral nerve sheath tumors can be undertaken without en bloc resection of the entire nerve trunk.

Muscle and nerve biopsies: techniques for the neurologist and neurosurgeon.

OBJECTIVE: Muscle and nerve biopsies are commonly performed procedures for the diagnosis of neuromuscular disorders. Neurologists and neurosurgeons are often consulted to perform these procedures in clinical practice. We provide guidelines in the performance of muscle and nerve biopsies. METHODS: We describe the technique for performance of muscle and nerve biopsy, and review the relevant literature. RESULTS: The quadriceps muscle is the most typical biopsy site for most myopathies, whereas the sural nerve is the most common nerve biopsy site for most peripheral neuropathies. Other sites may be utilized depending upon the pattern of symptoms or the differential diagnosis. Motor nerves may be sampled in the setting of motor neuron disease, for example. We advocate the use of conduit repair to allow for sensory or motor recovery to occur following nerve biopsy. CONCLUSION: The muscle biopsy and nerve biopsy may be performed with high yield, low morbidity, and rare complications.

Convection enhanced drug delivery of BDNF through a microcannula in a rodent model to strengthen connectivity of a peripheral motor nerve bridge model to bypass spinal cord injury.

Models employing peripheral nerve to bypass spinal cord injury (SCI), although highly promising, may benefit from improved nerve regeneration and motor bridge connectivity. Recent studies have demonstrated that neuronal growth factor-induced enhancement of endogenous neurorestoration may improve neuronal connectivity after severe neurologic injury, particularly if delivered intraparenchymally with zero-order kinetics. We sought to investigate the effect of convection-enhanced delivery of brain-derived neurotrophic factor (BDNF), a neuronal growth factor, on the connectivity of a peripheral motor-nerve bridge in a rodent model using electrophysiology and immunohistochemistry (IHC). Spinal cords of 29 female rats were hemisected at the L1 level. Ipsilateral T13 peripheral nerves were dissected from their muscular targets distally, while maintaining their connections with the spinal cord, and inserted caudal to the injury site to establish the nerve bridge. A microcannula attached to a six-week mini-osmotic pump was used to deliver either BDNF (n=12), saline (n=14), or fluorescein dye (n=3) directly into the spinal cord parenchyma between the site of nerve insertion and hemisection to a depth of 2mm into the area of the lateral motor pool. After four weeks, gastrocnemius muscle activation was assessed electromyographically in five animals from each group. Spinal cords were harvested and analyzed with IHC for cannula-associated injury, and nerve regeneration. Strength of motor bridge connection was illustrated by electrophysiology data. Intraspinal BDNF levels were measured using enzyme-linked immunosorbent assay. IHC revealed increased intraparenchymal BDNF concentration at the nerve bridge insertion site with evidence of minimal trauma from cannulation. BDNF infusion resulted in stronger connections between bridge nerves and spinal motor axons. Bridge nerve electrical stimulation in BDNF-treated rats evoked hind leg electromyogram responses of shorter latency and larger amplitudes than saline-infused controls. Thus, direct convection-assisted delivery provides reliable administration of potent growth factors directly into the spinal cord parenchyma. Delivery of BDNF at the peripheral nerve bridge site results in enhanced connectivity of the peripheral motor bridge in a rodent model of SCI.

Spinal cord bypass surgery with intercostal and spinal accessory nerves: an anatomical feasibility study in human cadavers.

OBJECT: Despite extensive study, no meaningful progress has been made in encouraging healing and recovery across the site of spinal cord injury (SCI) in humans. Spinal cord bypass surgery is an unconventional strategy in which intact peripheral nerves rostral to the level of injury are transferred into the spinal cord below the injury. This report details the feasibility of using spinal accessory nerves to bypass cervical SCI and intercostal nerves to bypass thoracolumbar SCI in human cadavers. METHODS: Twenty-three human cadavers underwent cervical and/or lumbar laminectomy and dural opening to expose the cervical cord and/or conus medullaris. Spinal accessory nerves were harvested from the Erb point to the origin of the nerve's first major branch into the trapezius. Intercostal nerves from the T6-12 levels were dissected from the lateral border of paraspinal muscles to the posterior axillary line. The distal ends of dissected nerves were then transferred medially and sequentially inserted 4 mm deep into the ipsilateral cervical cord (spinal accessory nerve) or conus medullaris (intercostals). The length of each transferred nerve was measured, and representative distal and proximal cross-sections were preserved for axonal counting. RESULTS: Spinal accessory nerves were consistently of sufficient length to be transferred to caudal cervical spinal cord levels (C4-8). Similarly, intercostal nerves (from T-7 to T-12) were of sufficient length to be transferred in a tension-free manner to the conus medullaris. Spinal accessory data revealed an average harvested nerve length of 15.85 cm with the average length needed to reach C4-8 of 4.7, 5.9, 6.5, 7.1, and 7.8 cm. The average length of available intercostal nerve from each thoracic level compared with the average length required to reach the conus medullaris in a tension-free manner was determined to be as follows (available, required in cm): T-7 (18.0, 14.5), T-8 (18.7, 11.7), T-9 (18.8, 9.0), T-10 (19.6, 7.0), T-11 (18.8, 4.6), and T-12 (15.8, 1.5). The number of myelinated axons present on cross-sectional analysis predictably decreased along both spinal accessory and intercostal nerves as they coursed distally. CONCLUSIONS: Both spinal accessory and intercostal nerves, accessible from a posterior approach in the prone position, can be successfully harvested and transferred to their respective targets in the cervical spinal cord and conus medullaris. As expected, the number of axons available to grow into the spinal cord diminishes distally along each nerve. To maximize axon "bandwidth" in nerve bypass procedures, the most proximal section of the nerve that can be transferred in a tension-free manner to a spinal level caudal to the level of injury should be implanted. This study supports the feasibility of SAN and intercostal nerve transfer as a means of treating SCI and may assist in the preoperative selection of candidates for future human clinical trials of cervical and thoracolumbar SCI bypass surgery.

Spinal infusion pump-catheter leak detected by high-resolution 3D computed tomography.

Implanted intrathecal drug delivery systems may malfunction as a result of fracture of the intrathecal catheter. A suspected catheter fracture not seen on plain radiographs of the catheter system will typically prompt a contrast-enhanced imaging study of the pump. Injection of iodinated contrast medium into the pump system with routine fluoroscopy can sometimes fail to reveal subtle leaks. The authors present a case demonstrating the utility of high-resolution, 3D-CT for intrathecal pump-catheter system interrogation when routine fluoroscopy is unrevealing. In this case, a catheter leak was suspected on the basis of the patient's history, but no obvious fracture was noted on plain radiographs. An intraoperative fluoroscopic study that included multiple injections of contrast medium into the catheter system failed to conclusively show a catheter leak. The authors therefore performed a post-injection 3D-CT study, which clearly demonstrated a leak from the intrathecal catheter just deep to the thoracolumbar fascia. The leak was visible on source images and was especially obvious after 3D reconstruction. This led to surgical revision of the catheter and subsequent resumption of normal pump function. The authors therefore suggest that if a leak is suspected in an implanted intrathecal catheter and routine contrast fluoroscopy is unrevealing, post-injection 3D-CT scanning should be performed to further investigate the possibility of a subtle leak.

Spinal nerve root stimulation.

Spinal nerve root stimulation (SNRS) is a neuromodulation technique that is used to treat chronic pain. This modality places stimulator electrode array(s) along the spinal nerve roots, creating stimulation paresthesias within the distribution of the target nerve root(s), thereby treating pain in that same distribution. There are several different forms of spinal nerve root stimulation, depending upon the exact electrode positioning along the nerve roots. SNRS combines the minimally invasive nature, central location, and ease of placement of spinal cord stimulation with the focal targeting of stimulation paresthesias of peripheral nerve stimulation. This hybrid technique may be an effective alternative for patients in whom other forms of neurostimulation are either ineffective or inappropriate.

Preclinical evaluation of postischemic dehydroascorbic Acid administration in a large-animal stroke model.

Dehydroascorbic acid (DHA), a blood-brain barrier transportable form of ascorbic acid, confers robust neuroprotection following murine stroke. In an effort to translate this promising neuroprotective strategy into human clinical trial, we evaluated postischemic DHA administration in a large-animal stroke model. Thirty-six adult male baboons were initially randomized to undergo transorbital craniectomy to induce transient cerebral artery occlusion and to receive postischemic dosing of either 500 mg/kg of DHA or vehicle. Primary outcomes included infarct volume, determined by magnetic resonance imaging, as well as neurological function evaluated on the day of sacrifice. The midpoint interim analysis (n = 9 per cohort) revealed that DHA administration did not significantly improve either infarct volume or neurological function. The study was terminated after a determination of statistical futility. We were unable to confirm a neuroprotective effect for postischemic DHA administration in our large-animal model using a dosing scheme that was previously successful in rodents. Further analysis of the efficacy of DHA administration must thus be undertaken prior to clinical translation.