A technique for repeated blood and cerebrospinal fluid sampling from individual rats over time without the need for repeated anesthesia

Ethical animal use follows the 3R's: Replacement, Reduction and Refinement. Here, we present the use of simultaneous jugular vein and cisterna magna catheterization via a port system in rats for repeated fluid sampling for 14 consecutive days without loss of catheter patency. This technique allows repeated intra-animal sampling without anesthesia and, if used with pooling samples from a cohort of animals, replaces the need for terminal collections for sufficient sample volumes.

Association of plasma biomarkers with cognition, cognitive decline, and daily function across and within neurodegenerative diseases: Results from the Ontario Neurodegenerative Disease Research Initiative

INTRODUCTION

We investigated whether novel plasma biomarkers are associated with cognition, cognitive decline, and functional independence in activities of daily living across and within neurodegenerative diseases.

METHODS

Glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), phosphorylated tau (p-tau)181 and amyloid beta (Aβ)42/40 were measured using ultra-sensitive Simoa immunoassays in 44 healthy controls and 480 participants diagnosed with Alzheimer's disease/mild cognitive impairment (AD/MCI), Parkinson's disease (PD), frontotemporal dementia (FTD) spectrum disorders, or cerebrovascular disease (CVD).

RESULTS

GFAP, NfL, and/or p-tau181 were elevated among all diseases compared to controls, and were broadly associated with worse baseline cognitive performance, greater cognitive decline, and/or lower functional independence. While GFAP, NfL, and p-tau181 were highly predictive across diseases, p-tau181 was more specific to the AD/MCI cohort. Sparse associations were found in the FTD and CVD cohorts and for Aβ42/40 .

DISCUSSION

GFAP, NfL, and p-tau181 are valuable predictors of cognition and function across common neurodegenerative diseases, and may be useful in specialized clinics and clinical trials.

A methodological primer of extracellular vesicles isolation and characterization via different techniques

We present four different protocols of varying complexity for the isolation of cell culture-derived extracellular vesicles (EVs)/exosome-enriched fractions with the objective of providing researchers with easily conducted methods that can be adapted for many different uses in various laboratory settings and locations. These protocols are primarily based on polymer precipitation, filtration and/or ultracentrifugation, as well as size-exclusion chromatography (SEC) and include: (i) polyethylene glycol and sodium chloride supplementation of the conditioned medium followed by low-speed centrifugation; (ii) ultracentrifugation of conditioned medium; (iii) filtration of conditioned media through a 100-kDa exclusion filter; and (iv) isolation using a standard commercial kit. These techniques can be followed by further purification by ultracentrifugation, sucrose density gradient centrifugation, or SEC if needed and the equipment is available. HEK293 and SH-SY5Y cell cultures were used to generate conditioned medium containing exosomes. This medium was then depleted of cells and debris, filtered through a 0.2-µM filter, and supplemented with protease and RNAse inhibitors prior to exosomal isolation. The purified EVs can be used immediately or stably stored at 4°C (up to a week for imaging or using intact EVS downstream) or at -80°C for extended periods and then used for biochemical study. Our aim is not to compare these methodologies but to present them with descriptors so that researchers can choose the "best method" for their work under their individual conditions.

New metal-organic framework coated sodium alginate for the delivery of curcumin as a sustainable drug delivery and cancer therapy system

The utilization of biocompatible drug delivery systems with extended drug release capabilities is highly advantageous in cancer therapy, as they can mitigate adverse effects. To establish such a biocompatible system with prolonged drug release behavior, researchers developed an innovative drug carrier. In this study, a sustainable approach was employed to synthesize a new zinc-based metal-organic framework (Zn-MOF) through the reaction between synthesized Schiff base ligands and zinc ions. Comprehensive analyses, including FT-IR, XRD, SEM, BET surface area, and TGA techniques, were employed to thoroughly characterize the frameworks. Following comprehensive characterization, curcumin (CUR) was loaded onto the Zn-MOF, resulting in CUR entrapment efficiency and loading capacity of 79.23 % and 26.11 %, respectively. In vitro evaluations of CUR release from CUR@MOF exhibited controlled release patterns, releasing 78.9 % and 50.0 % of CUR at pH 5.0 and pH 7.4, respectively. To mitigate initial burst release, a coating of the biopolymer sodium alginate (SA) was applied to CUR@Zn-MOF. In vitro CUR release tests indicated that SA/CUR@Zn-MOF outperformed pristine CUR@Zn-MOF. The release of CUR conformed to the Korsmeyer-Peppas model, displaying non-Fickian diffusion. Furthermore, an in vitro cytotoxicity study clearly demonstrated the potent anti-tumor activity of the synthesized CUR@Zn-MOF attributed to its controlled release of CUR. This led to the induction of apoptotic effects and cell death across HeLa, HEK293, and SH-SY5Y cell lines. These findings strongly suggest that the developed pH-sensitive carriers hold remarkable potential as targeted vehicles for drug delivery in cancer therapy.

Upregulation of LRRK2 following traumatic brain injury does not directly phosphorylate Thr175 tau

Phosphorylated microtubule-associated protein tau (tau) aggregates are a pathological hallmark of various neurodegenerative diseases, including chronic traumatic encephalopathy and amyotrophic lateral sclerosis with cognitive impairment. While there are many residues phosphorylated on tau, phosphorylation of threonine 175 (pThr175 tau) has been shown to initiate fibril formation in vitro and is present in pathological tau aggregates in vivo. Given this, preventing Thr175 tau phosphorylation presents a potential approach to reduce fibril formation; however, the kinase(s) acting on Thr175 are not yet fully defined. Using a single controlled cortical impact rodent model of traumatic brain injury (TBI), which rapidly induces Thr175 tau phosphorylation, we observed an upregulation and alteration in subcellular localization of leucine-rich repeat kinase 2 (LRRK2), a kinase that has been implicated in tau phosphorylation. LRRK2 upregulation was evident by one-day post-injury and persisted to day 10. The most notable changes were observed in microglia at the site of injury in the cortex. To determine if the appearance of pThr175 tau was causally related to the upregulation of LRRK2 expression, we examined the ability of LRRK2 to phosphorylate Thr175in vitro by co-transfecting 2N4R human WT-tau with either LRRK2-WT, constitutively-active LRRK2-G2019S or inactive LRRK2-3XKD. We found no significant difference in the level of pThr175 tau between the overexpression of LRRK2-WT, -G2019S or -3XKD, suggesting LRRK2 does not phosphorylate tau at Thr175. Further, downstream events known to follow Thr175 phosphorylation and known to be associated with pathological tau fibril formation (pSer9-GSK3β and pThr231 tau induction) also remained unchanged. We conclude that while LRRK2 expression is altered in TBI, it does not contribute directly to pThr175 tau generation.

Local Control in Patients with Metastatic Renal Cell Carcinoma to the Spine: The Experience of an Institution with a Multidisciplinary Spine Oncology Program

BACKGROUND

The outcomes for patients with metastatic renal cell carcinoma (RCC) to the spine who underwent stereotactic body radiotherapy (SBRT) through a multidisciplinary spine oncology program are not well described. We sought to describe the clinical course and local control rates at 1 and 2 years for these patients.

METHODS

A retrospective analysis of a prospectively maintained database of adult oncologic patients receiving SBRT to the spine through a multidisciplinary spine oncology program at a single institution from 2010 to 2021 was performed. Patients with a pathologic diagnosis of RCC were included.

RESULTS

A total of 75 spinal sites were treated in 60 patients. Of the 60 patients, 75.0% were men, and the mean patient age was 59.2 ± 11.3 years. At 1 year after treatment, 6 of the 60 patients were lost to follow-up. Of the remaining 54 patients, 18 were censored by death and 7 treatment sites showed local recurrence, for 37 of 44 treatment sites with local control (87.8%). At 2 years, 1 additional local recurrence had developed, 15 patients were censored by death, and no additional patients had been lost to follow-up, resulting in 28 of 36 treatment sites with local control (83.2%). None of the patients who had undergone repeat SBRT had local recurrence at 1 or 2 years. For those with local recurrence, the average time from treatment to progression was 6.6 ± 6.5 months.

CONCLUSIONS

In this cohort, one of the largest reported studies of spine SBRT for metastatic RCC, local control was high at 1 and 2 years. Our findings support the role of coordinated, algorithmic treatment for these patients.

Patients with progression of spinal metastases who present to the clinic have better outcomes compared to those who present to the emergency department

BACKGROUND

As cancer therapies have improved, spinal metastases are increasingly common. Resulting complications have a significant impact on patient's quality of life. Optimal methods of surveillance and avoidance of neurologic deficits are understudied. This study compares the clinical course of patients who initially presented to the emergency department (ED) versus a multidisciplinary spine oncology clinic and who underwent stereotactic body radiation therapy (SBRT) secondary to progression/presentation of metastatic spine disease.

METHODS

We performed a retrospective analysis of a prospectively maintained database of adult oncologic patients who underwent spinal SBRT at a single hospital from 2010 to 2021. Descriptive statistics and survival analyses were performed.

RESULTS

We identified 498 spinal radiographic treatment sites in 390 patients. Of these patients, 118 (30.3%) presented to the ED. Patients presenting to the ED compared to the clinic had significantly more severe spinal compression (52.5% vs. 11.7%; p < 0.0001), severe pain (28.8% vs. 10.3%; p < 0.0001), weakness (24.5% vs. 4.5%; p < 0.0001), and difficulty walking (24.5% vs. 4.5%; p < 0.0001). Patients who presented to the ED compared to the clinic were significantly more likely to have surgical intervention followed by SBRT (55.4% vs. 15.3%; p < 0.0001) compared to SBRT alone. Patients who presented to the ED compared to the clinic had a significantly quicker interval to distant spine progression (5.1 ± 6.5 vs. 9.1 ± 10.2 months; p = 0.004), systemic progression (5.1 ± 7.2 vs. 9.2 ± 10.7 months; p < 0.0001), and worse overall survival (9.3 ± 10.0 vs. 14.3 ± 13.7 months; p = 0.002).

CONCLUSION

The establishment of multidisciplinary spine oncology clinics is an opportunity to potentially allow for earlier, more data-driven treatment of their spinal metastatic disease.

SARS-CoV-2, aging, and Post-COVID-19 neurodegeneration

As the world continues to experience the effects of SARS-CoV-2, there is evidence to suggest that the sequelae of viral infection (the post-COVID-19 condition; PCC) at both an individual and population level will be significant and long-lasting. The history of pandemics or epidemics in the last 100 years caused by members of the RNA virus family, of which coronaviruses are a member, provides ample evidence of the acute neurological effects. However, except for the H1N1 influenza pandemic of 1918/1919 (the Spanish flu) with its associated encephalitis lethargica, there is little information on long-term neurological sequelae. COVID-19 is the first pandemic that has occurred in a setting of an aging population, especially in several high-income countries. Its survivors are at the greatest risk for developing neurodegenerative conditions as they age, rendering the current pandemic a unique paradigm not previously witnessed. The SARS-CoV-2 virus, among the largest of the RNA viruses, is a single-stranded RNA that encodes for 29 proteins that include the spike protein that contains the key domains required for ACE2 binding, and a complex array of nonstructural proteins (NSPs) and accessory proteins that ensure the escape of the virus from the innate immune response, allowing for its efficient replication, translation, and exocytosis as a fully functional virion. Increasingly, these proteins are also recognized as potentially contributing to biochemical and molecular processes underlying neurodegeneration. In addition to directly being taken up by brain endothelium, the virus or key protein constituents can be transported to neurons, astrocytes, and microglia by extracellular vesicles and can accelerate pathological fibril formation. The SARS-CoV-2 nucleocapsid protein is intrinsically disordered and can participate in liquid condensate formation, including as pathological heteropolymers with neurodegenerative disease-associated RNA-binding proteins such as TDP-43, FUS, and hnRNP1A. As the SARS-CoV-2 virus continues to mutate under the immune pressure exerted by highly efficacious vaccines, it is evolving into a virus with greater transmissibility but less severity compared with the original strain. The potential of its lingering impact on the nervous system thus has the potential to represent an ongoing legacy of an even greater global health challenge than acute infection.

Targeted Public Health Training for Neurosurgeons: An Essential Task for the Prioritization of Neurosurgery in the Evolving Global Health Landscape

The gap between the tremendous burden of neurological disease requiring surgical management and the limited capacity for neurosurgical care has fueled the growth of the global neurosurgical movement. It is estimated that an additional 23 300 neurosurgeons are needed to meet the burden posed by essential cases across the globe. Initiatives to increase neurosurgical capacity through systems strengthening and workforce development are key elements in correcting this deficit. Building on the growing interest in global health among neurosurgical trainees, we propose the integration of targeted public health education into neurosurgical training, in both high-income countries and low- and middle-income countries. This effort will ensure that graduates possess the fundamental skillsets and experience necessary to participate in and lead capacity-building efforts in the developing countries. This additional public health training can also help neurosurgical residents to achieve the core competencies outlined by accreditation boards, such as the Accreditation Committee on Graduate Medical Education in the United States. In this narrative review, we describe the global burden of neurosurgical disease, establish the need and role for the global neurosurgeon, and discuss pathways for implementing targeted global public health education in the field of neurosurgery.

Characteristics of the Ontario Neurodegenerative Disease Research Initiative cohort

INTRODUCTION

Understanding synergies between neurodegenerative and cerebrovascular pathologies that modify dementia presentation represents an important knowledge gap.

METHODS

This multi-site, longitudinal, observational cohort study recruited participants across prevalent neurodegenerative diseases and cerebrovascular disease and assessed participants comprehensively across modalities. We describe univariate and multivariate baseline features of the cohort and summarize recruitment, data collection, and curation processes.

RESULTS

We enrolled 520 participants across five neurodegenerative and cerebrovascular diseases. Median age was 69 years, median Montreal Cognitive Assessment score was 25, median independence in activities of daily living was 100% for basic and 93% for instrumental activities. Spousal study partners predominated; participants were often male, White, and more educated. Milder disease stages predominated, yet cohorts reflect clinical presentation.

DISCUSSION

Data will be shared with the global scientific community. Within-disease and disease-agnostic approaches are expected to identify markers of severity, progression, and therapy targets. Sampling characteristics also provide guidance for future study design.

Finding Common Ground on the Site of Onset of Amyotrophic Lateral Sclerosis

The fundamental origin of amyotrophic lateral sclerosis (ALS) has remained an enigma since its earliest description as a relentlessly progressive degeneration with prominent neuromuscular manifestations that are associated with upper and lower motor neuron dysfunction. Although this remains the hallmark of ALS, a significant proportion of patients will also demonstrate one or more features of frontotemporal dysfunction, including a frontotemporal dementia (FTD). Understanding whether these 2 seemingly disparate syndromes are simply reflective of the co-occurrence of 2 distinct pathologic processes or the clinical manifestations of a common pathophysiologic derangement involving the brain more widely has gripped contemporary ALS researchers. Supporting a commonality of causation, both ALS and FTD show an alteration in the metabolism of TAR DNA-binding protein 43, marked by a shift in nucleocytoplasmic localization alongside a broad range of neuronal cytoplasmic inclusions consisting of pathologic aggregates of RNA-binding proteins. Similarly, several disease-associated or disease-modifying genetic variants that are shared between the 2 disorders suggest shared underlying mechanisms. In both, a prominent glial response has been postulated to contribute to non-cell-autonomous spread. A more contemporary hypothesis, however, suggests that syndromes of cortical and subcortical dysfunction are driven by impairments in discrete neural networks. This postulates that such networks, including networks subserving motor or cognitive function, possess unique and selective vulnerabilities to either single molecular toxicities or combinations thereof. The co-occurrence of one or more network dysfunctions in ALS and FTD is thus a reflection not of unique neuroanatomic correlates but rather of shared molecular vulnerabilities. The basis of such shared vulnerabilities becomes the fulcrum around which the next advances in our understanding of ALS and its possible therapy will develop.

Neurosurgery Subspecialty Practice During a Pandemic: A Multicenter Analysis of Operative Practice in 7 U.S. Neurosurgery Departments During Coronavirus Disease 2019

OBJECTIVE

Changes to neurosurgical practices during the coronavirus disease 2019 (COVID-19) pandemic have not been thoroughly analyzed. We report the effects of operative restrictions imposed under variable local COVID-19 infection rates and health care policies using a retrospective multicenter cohort study and highlight shifts in operative volumes and subspecialty practice.

METHODS

Seven academic neurosurgery departments' neurosurgical case logs were collected; procedures in April 2020 (COVID-19 surge) and April 2019 (historical control) were analyzed overall and by 6 subspecialties. Patient acuity, surgical scheduling policies, and local surge levels were assessed.

RESULTS

Operative volume during the COVID-19 surge decreased 58.5% from the previous year (602 vs. 1449, P = 0.001). COVID-19 infection rates within departments' counties correlated with decreased operative volume (r = 0.695, P = 0.04) and increased patient categorical acuity (P = 0.001). Spine procedure volume decreased by 63.9% (220 vs. 609, P = 0.002), for a significantly smaller proportion of overall practice during the COVID-19 surge (36.5%) versus the control period (42.0%) (P = 0.02). Vascular volume decreased by 39.5% (72 vs. 119, P = 0.01) but increased as a percentage of caseload (8.2% in 2019 vs. 12.0% in 2020, P = 0.04). Neuro-oncology procedure volume decreased by 45.5% (174 vs. 318, P = 0.04) but maintained a consistent proportion of all neurosurgeries (28.9% in 2020 vs. 21.9% in 2019, P = 0.09). Functional neurosurgery volume, which declined by 81.4% (41 vs. 220, P = 0.008), represented only 6.8% of cases during the pandemic versus 15.2% in 2019 (P = 0.02).

CONCLUSIONS

Operative restrictions during the COVID-19 surge led to distinct shifts in neurosurgical practice, and local infective burden played a significant role in operative volume and patient acuity.

Navigated retrodiaphragmatic/retroperitoneal approach for the treatment of symptomatic kyphoscoliosis: an operative video

Retropleural, retrodiaphragmatic, and retroperitoneal approaches are utilized to access difficult thoracolumbar junction (T10–L2) pathology. The authors present a 58-year-old man with chronic low-back pain who failed years of conservative therapy. Preoperative radiographs demonstrated significant levoconvex scoliosis with coronal and sagittal imbalance. He underwent a retrodiaphragmatic/retroperitoneal approach for T12–L1, L1–2, L2–3, and L3–4 interbody release and fusion in conjunction with second-stage facet osteotomies, L4–5 TLIF, and T10–iliac posterior instrumented fusion. This video focuses on the retrodiaphragmatic approach assisted by 3D navigation.

The video can be found here: https://stream.cadmore.media/r10.3171/2022.3.FOCVID2215

Differential immune landscapes in appendicular versus axial skeleton

Roughly 400,000 people in the U.S. are living with bone metastases, the vast majority occurring in the spine. Metastases to the spine result in fractures, pain, paralysis, and significant health care costs. This predilection for cancer to metastasize to the bone is seen across most cancer histologies, with the greatest incidence seen in prostate, breast, and lung cancer. The molecular process involved in this predilection for axial versus appendicular skeleton is not fully understood, although it is likely that a combination of tumor and local micro-environmental factors plays a role. Immune cells are an important constituent of the bone marrow microenvironment and many of these cells have been shown to play a significant role in tumor growth and progression in soft tissue and bone disease. With this in mind, we sought to examine the differences in immune landscape between axial and appendicular bones in the normal noncancerous setting in order to obtain an understanding of these landscapes. To accomplish this, we utilized mass cytometry by time-of-flight (CyTOF) to examine differences in the immune cell landscapes between the long bone and vertebral body bone marrow from patient clinical samples and C57BL/6J mice. We demonstrate significant differences between immune populations in both murine and human marrow with a predominance of myeloid progenitor cells in the spine. Additionally, cytokine analysis revealed differences in concentrations favoring a more myeloid enriched population of cells in the vertebral body bone marrow. These differences could have clinical implications with respect to the distribution and permissive growth of bone metastases.

Syrinx regression after correction of iatrogenic kyphotic deformity: illustrative case

BACKGROUND

Syringomyelia has a long-established association with pediatric scoliosis, but few data exist on the relationship of syringomyelia to pediatric kyphotic deformities.

OBSERVATIONS

This report reviewed a unique case of rapid and sustained regression of syringomyelia in a 13-year-old girl after surgical correction of iatrogenic kyphotic deformity.

LESSONS

In cases of syringomyelia associated with acquired spinal deformity, treatment of deformity to resolve an associated subarachnoid block should be considered because it may obviate the need for direct treatment of syrinx.

Pre- and intraoperative thoracic spine localization techniques: a systematic review

OBJECTIVE

In the era of modern medicine with an armamentarium full of state-of-the art technologies at our disposal, the incidence of wrong-level spinal surgery remains problematic. In particular, the thoracic spine presents a challenge for accurate localization due partly to body habitus, anatomical variations, and radiographic artifact from the ribs and scapula. The present review aims to assess and describe thoracic spine localization techniques.

METHODS

The authors performed a literature search using the PubMed database from 1990 to 2020, compliant with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A total of 27 articles were included in this qualitative review.

RESULTS

A number of pre- and intraoperative strategies have been devised and employed to facilitate correct-level localization. Some of the more well-described approaches include fiducial metallic markers (screw or gold), metallic coils, polymethylmethacrylate, methylene blue, marking wire, use of intraoperative neuronavigation, intraoperative localization techniques (including using a needle, temperature probe, fluoroscopy, MRI, and ultrasonography), and skin marking.

CONCLUSIONS

While a number of techniques exist to accurately localize lesions in the thoracic spine, each has its advantages and disadvantages. Ultimately, the localization technique deployed by the spine surgeon will be patient-specific but often based on surgeon preference.

Resection of a Lumbar Intradural Extramedullary Schwannoma: 2-Dimensional Operative Video

Schwannomas are typically benign tumors that arise from the sheaths of nerves in the peripheral nervous system. In the spine, schwannomas usually arise from spinal nerve roots and are therefore extramedullary in nature. Surgical resection-achieving a gross total resection, is the main treatment modality and is typically curative for patients with sporadic tumors. In this video, we present the case of a 38-yr-old male with worsening left leg radiculopathy, found to have a lumbar schwannoma. Preoperative imaging demonstrated that the tumor was at the level of L4-L5. A laminectomy at this level was performed with gross total resection of the tumor. The key points of the video include use of intraoperative fluoroscopy to confirm surgical level and help plan surgical exposure, use of ultrasound for intradural tumor localization, and advocating for maximum safe resection using neurostimulation. The patient tolerated the surgery well without any complications. He was discharged home with no additional therapy needed. Appropriate patient consent was obtained.

Lumbar Laminoplasty for Resection of Myxopapillary Ependymoma of the Conus Medullaris: 2-Dimensional Operative Video

Myxopapillary ependymomas are slow-growing tumors that are located almost exclusively in the region of the conus medullaris, cauda equina, and filum terminale of the spinal cord. Surgical intervention achieving a gross total resection is the main treatment modality. If, however, a gross total resection cannot be achieved, surgery is augmented with radiation therapy. In this video, we present the case of a 27-yr-old male with persistent back pain and radiculopathy who was found to have a myxopapillary ependymoma that was adherent to the conus. Preoperative imaging demonstrated that the tumor was displacing the conus and nerve roots ventrally. A laminoplasty at L1-L2 was performed with near-total resection because of the intimate involvement of neural tissue. The key features of the video include performing laminoplasty and rationale, and performing maximum safe tumor resection with a combination of bipolar cautery, suction, and ultrasonic aspiration augmented with frequent stimulation, gel foam pledgets intradurally, and achieving a watertight closure of the dura and fascia. The patient tolerated the surgery well without any complications. Given his gross residual disease along the conus and young age, he was at a high risk for continued tumor growth without adjuvant therapy, with a recurrence rate of roughly 33% to 45% in patients who underwent subtotal resection. With the addition of adjuvant radiation therapy, the recurrence rate is 20% to 29%.1,2 He was discharged to home with a plan for conventional fractionated external beam radiation. At the most recent follow-up, he reported decreased back pain and radiculopathy. Appropriate patient consent was obtained.

Cervical 1-2 Posterior Instrumented Fusion Utilizing Computer-Assisted Navigation With Harvest of Rib Strut Autograft: 2-Dimensional Operative Video

Nonunion of a type II odontoid fracture after the placement of an anterior odontoid screw can occur despite careful patient selection. Countervailing factors to successful fusion include the vascular watershed zone between the odontoid process and body of C2 as well as the relatively low surface area available for fusion. Patient-specific factors include osteoporosis, advanced age, and poor fracture fragment apposition. Cervical 1-2 posterior instrumented fusion is indicated for symptomatic nonunion. The technique leverages the larger posterolateral surface area for fusion and does not rely on bony growth in a watershed zone. Although loss of up to half of cervical rotation is expected after C1-2 arthrodesis, this may be better tolerated in the elderly, who may have lower physical demands than younger patients. In this video, we discuss the case of a 75-yr-old woman presenting with intractable mechanical cervicalgia 7 mo after sustaining a type II odontoid fracture and undergoing anterior odontoid screw placement at an outside institution. Cervical radiography and computed tomography exhibited haloing around the screw and nonunion across the fracture. We demonstrate C1-2 posterior instrumented fusion with Goel-Harms technique (C1 lateral mass and C2 pedicle screws), utilizing computer-assisted navigation, and modified Sonntag technique with rib strut autograft. Posterior C1-2-instrumented fusion with rib strut autograft is an essential technique in the spine surgeon's armamentarium for the management of C1-2 instability, which can be a sequela of type II dens fracture. Detailed video demonstration has not been published to date. Appropriate patient consent was obtained.

Navigation and Robotic-Assisted Single-Position Prone Lateral Lumbar Interbody Fusion: Technique, Feasibility, Safety, and Case Series

BACKGROUND

Single-position prone lateral interbody fusion is a recently introduced technical modification of the minimally invasive retroperitoneal transpsoas approach for lateral lumbar interbody fusion (LLIF). Several technical descriptions of single-position prone LLIF have been published with traditional fluoroscopy for guidance. However, there has been no investigation of either three-dimensional computed tomography-based navigation for prone LLIF or integration with robotic assistance platforms with the prone lateral technique. This study evaluated the feasibility and safety of spinal navigation and robotic assistance for single-position prone LLIF.

METHODS

Retrospective review of medical records and a prospectively acquired database for a single center was performed to examine immediate and 30-day clinical and radiographic outcomes for consecutive patients undergoing single-position prone LLIF with spinal navigation and/or robotic assistance.

RESULTS

Nine patients were treated, 4 women and 5 men. Mean age was 65.4 years (range, 46-75 years), and body mass index was 30.2 kg/m² (range, 24-38 kg/m²). The most common surgical indication was adjacent segment disease (44.4%), followed by pseudarthrosis (22.2%), spondylolisthesis (11.1%), degenerative disc disease (11.1%), and recurrent stenosis (11.1%). Postoperative approach-related complications included pain-limited bilateral hip flexor weakness (4/5) and pain-limited left knee extension weakness (4/5) in 1 patient (11.1%) and right lateral thigh numbness and dysesthesia in 1 patient (11.1%). All cages were placed within quarters 2-3, signifying the middle portion of the disc space. There were no instances of misguidance by navigation.

CONCLUSIONS

Integration of spinal navigation and robotic assistance appears feasible, accurate, and safe as an alternative to fluoroscopic guidance for single-position LLIF.

The Integral Role of RNA in Stress Granule Formation and Function

Stress granules (SGs) are phase-separated, membraneless, cytoplasmic ribonucleoprotein (RNP) assemblies whose primary function is to promote cell survival by condensing translationally stalled mRNAs, ribosomal components, translation initiation factors, and RNA-binding proteins (RBPs). While the protein composition and the function of proteins in the compartmentalization and the dynamics of assembly and disassembly of SGs has been a matter of study for several years, the role of RNA in these structures had remained largely unknown. RNA species are, however, not passive members of RNA granules in that RNA by itself can form homo and heterotypic interactions with other RNA molecules leading to phase separation and nucleation of RNA granules. RNA can also function as molecular scaffolds recruiting multivalent RBPs and their interactors to form higher-order structures. With the development of SG purification techniques coupled to RNA-seq, the transcriptomic landscape of SGs is becoming increasingly understood, revealing the enormous potential of RNA to guide the assembly and disassembly of these transient organelles. SGs are not only formed under acute stress conditions but also in response to different diseases such as viral infections, cancer, and neurodegeneration. Importantly, these granules are increasingly being recognized as potential precursors of pathological aggregates in neurodegenerative diseases. In this review, we examine the current evidence in support of RNA playing a significant role in the formation of SGs and explore the concept of SGs as therapeutic targets.

Spinal arthrodesis via lumbar interbody fusion without direct decompression as a treatment for recurrent radicular pain due to epidural fibrosis: patient series

BACKGROUND

Lumbar radiculopathy is the most common indication for lumbar discectomy, but residual postoperative radicular symptoms are common. Postoperative lumbar radiculopathy secondary to scar formation is notoriously difficult to manage, with the mainstay of treatment focused on nonoperative techniques. Surgical intervention for epidural fibrosis has shown unacceptably high complication rates and poor success rates.

OBSERVATIONS

Three patients underwent spinal arthrodesis without direct decompression for recurrent radiculopathy due to epidural fibrosis. Each patient previously underwent lumbar discectomy but subsequently developed recurrent radiculopathy. Imaging revealed no recurrent disc herniation, although it demonstrated extensive epidural fibrosis and scar in the region of the nerve root at the previous surgical site. Dynamic radiographs showed no instability. Two patients underwent lateral lumbar interbody fusion, and one patient underwent anterior lumbosacral interbody fusion. Each patient experienced resolution of radicular symptoms by the 1-year follow-up. Average EQ visual analog scale scores improved from 65 preoperatively to 78 postoperatively.

LESSONS

Spinal arthrodesis via lumbar interbody fusion, without direct decompression, may relieve pain in patients with recurrent radiculopathy due to epidural fibrosis, even in the absence of gross spinal instability.

Dura promotes metastatic potential in prostate cancer through the CXCR2 pathway

PURPOSE

Spinal metastases are common in cancer. This preferential migration/growth in the spine is not fully understood. Dura has been shown to affect the surrounding microenvironment and promote cancer growth. Here, we investigate the role of dural cytokines in promoting the metastatic potential of prostate cancer (PCa) and the involvement of the CXCR2 signaling pathway.

METHODS

The role of dural conditioned media (DCM) in proliferation, migration and invasion of five PCa cell lines with various hormone sensitivities was assessed in the presence or absence of the CXCR2 inhibitor, SB225002. CXCR2 surface protein was examined by FACS. Cytokine levels were measured using a mouse cytokine array.

RESULTS

We observed high levels of cytokines produced by dura and within the vertebral body bone marrow, namely CXCL1 and CXCL2, that act on the CXCR2 receptor. All prostate cell lines treated with DCM demonstrated significant increase in growth, migration and invasion regardless of androgen sensitivity, except PC3, which did not significantly increase in invasiveness. When treated with SB225002, the growth response to DCM by cells expressing the highest levels of CXCR2 as measured by FACS (LNCaP and 22Rv1) was blunted. The increase in migration was significantly decreased in all lines in the presence of SB225002. Interestingly, the invasion increase seen with DCM was unchanged when these cells were treated with the CXCR2 inhibitor, except PC3 did demonstrate a significant decrease in invasion.

CONCLUSION

DCM enhances the metastatic potential of PCa with increased proliferation, migration and invasion. This phenomenon is partly mediated through the CXCR2 pathway.

Repetitive mild traumatic brain injury in mice triggers a slowly developing cascade of long-term and persistent behavioral deficits and pathological changes

We have previously reported long-term changes in the brains of non-concussed varsity rugby players using magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI) and functional magnetic imaging (fMRI). Others have reported cognitive deficits in contact sport athletes that have not met the diagnostic criteria for concussion. These results suggest that repetitive mild traumatic brain injuries (rmTBIs) that are not severe enough to meet the diagnostic threshold for concussion, produce long-term consequences. We sought to characterize the neuroimaging, cognitive, pathological and metabolomic changes in a mouse model of rmTBI. Using a closed-skull model of mTBI that when scaled to human leads to rotational and linear accelerations far below what has been reported for sports concussion athletes, we found that 5 daily mTBIs triggered two temporally distinct types of pathological changes. First, during the first days and weeks after injury, the rmTBI produced diffuse axonal injury, a transient inflammatory response and changes in diffusion tensor imaging (DTI) that resolved with time. Second, the rmTBI led to pathological changes that were evident months after the injury including: changes in magnetic resonance spectroscopy (MRS), altered levels of synaptic proteins, behavioural deficits in attention and spatial memory, accumulations of pathologically phosphorylated tau, altered blood metabolomic profiles and white matter ultrastructural abnormalities. These results indicate that exceedingly mild rmTBI, in mice, triggers processes with pathological consequences observable months after the initial injury.

Evidence of synergism among three genetic variants in a patient with LMNA-related lipodystrophy and amyotrophic lateral sclerosis leading to a remarkable nuclear phenotype

Neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), can be clinically heterogeneous which may be explained by the co-inheritance of multiple genetic variants that modify the clinical course. In this study we examine variants in three genes in a family with one individual presenting with ALS and lipodystrophy. Sequencing revealed a p.Gly602Ser variant in LMNA, and two additional variants, one each in SETX (g.intron10-13delCTT) and FUS (p.Gly167_Gly168del). These latter genes have been linked to ALS. All family members were genotyped and each variant, and each combination of variants detected, were functionally evaluated in vitro regarding effects on cell survival, expression patterns and cellular phenotype. Muscle biopsy retrieved from the individual with ALS showed leakage of chromatin from the nucleus, a phenotype that was recapitulated in vitro with expression of all three variants simultaneously. Individually expressed variants gave cellular phenotypes there were unremarkable. Interestingly the FUS variant appears to be protective against the effects of the SETX and the LMNA variants on cell viability and may indicate loss of interaction of FUS with SETX and/or R-loops. We conclude that these findings support genetic modifications as an explanation of the clinical heterogeneity observed in human disease.

Survival, fusion, and hardware failure after surgery for spinal metastatic disease

OBJECTIVE

Decompression with instrumented fusion is commonly employed for spinal metastatic disease. Arthrodesis is typically sought despite limited knowledge of fusion outcomes, high procedural morbidity, and poor prognosis. This study aimed to describe survival, fusion, and hardware failure after decompression and fusion for spinal metastatic disease.

METHODS

The authors retrospectively examined a prospectively collected, single-institution database of adult patients undergoing decompression and instrumented fusion for spinal metastases. Patients were followed clinically until death or loss to follow-up. Fusion was assessed using CT when performed for oncological surveillance at 6-month intervals through 24 months postoperatively. Estimated cumulative incidences for fusion and hardware failure accounted for the competing risk of death. Potential risk factors were analyzed with univariate Fine and Gray proportional subdistribution hazard models.

RESULTS

One hundred sixty-four patients were identified. The mean age ± SD was 62.2 ± 10.8 years, 61.6% of patients were male, 98.8% received allograft and/or autograft, and 89.6% received postoperative radiotherapy. The Kaplan-Meier estimate of median survival was 11.0 months (IQR 3.5-37.8 months). The estimated cumulative incidences of any fusion and of complete fusion were 28.8% (95% CI 21.3%-36.7%) and 8.2% (95% CI 4.1%-13.9%). Of patients surviving 6 and 12 months, complete fusion was observed in 12.5% and 16.1%, respectively. The estimated cumulative incidence of hardware failure was 4.2% (95% CI 1.5-9.3%). Increasing age predicted hardware failure (HR 1.2, p = 0.003).

CONCLUSIONS

Low rates of complete fusion and hardware failure were observed due to the high competing risk of death. Further prospective, case-control studies incorporating nonfusion instrumentation techniques may be warranted.

Three-Dimensional Navigated Lateral Lumbar Interbody Fusion: 2-Dimensional Operative Video

Spondylolisthesis is a common cause of lower back and leg pain in adults. The initial treatment for patients is typically nonoperative in nature. However, when patients fail conservative management and their back and/or leg pain is recalcitrant, surgical intervention is warranted. Spinal decompression, either directly or indirectly, as well as fusion is often considered at this point. There are numerous approaches to fuse the spine, including anterior, lateral, or posterior, each with their own advantages and disadvantages.   This video illustrates a case of symptomatic spondylolisthesis occurring after laminectomy treated by lateral lumbar interbody fusion for indirect decompression and stabilization. The approach utilizes 3-dimensional navigation rather than traditional fluoroscopy, resulting in markedly decreased radiation exposure for the surgeon and staff while maintaining accuracy. Appropriate patient consent was obtained. This video demonstrates the technique for a lateral lumbar interbody fusion using navigation assistance, which is a minimally invasive technique for the treatment of spondylolisthesis.

Alterations in Tau Metabolism in ALS and ALS-FTSD

There is increasing acceptance that amyotrophic lateral sclerosis (ALS), classically considered a neurodegenerative disease affecting almost exclusively motor neurons, is syndromic with both clinical and biological heterogeneity. This is most evident in its association with a broad range of neuropsychological, behavioral, speech and language deficits [collectively termed ALS frontotemporal spectrum disorder (ALS-FTSD)]. Although the most consistent pathology of ALS and ALS-FTSD is a disturbance in TAR DNA binding protein 43 kDa (TDP-43) metabolism, alterations in microtubule-associated tau protein (tau) metabolism can also be observed in ALS-FTSD, most prominently as pathological phosphorylation at Thr¹⁷⁵ (pThr¹⁷⁵tau). pThr¹⁷⁵ has been shown to promote exposure of the phosphatase activating domain (PAD) in the tau N-terminus with the consequent activation of GSK3β mediated phosphorylation at Thr²³¹ (pThr²³¹tau) leading to pathological oligomer formation. This pathological cascade of tau phosphorylation has been observed in chronic traumatic encephalopathy with ALS (CTE-ALS) and in both in vivo and in vitro experimental paradigms, suggesting that it is of critical relevance to the pathobiology of ALS-FTSD. It is also evident that the co-existence of alterations in the metabolism of TDP-43 and tau acts synergistically in a rodent model to exacerbate the pathology of either.

Evidence of A Negative Feedback Network Between TDP-43 and miRNAs Dependent on TDP-43 Nuclear Localization

TAR DNA-binding protein 43 (TDP-43) is a DNA/RNA-binding protein that is integral to RNA processing. Among these functions is a critical role in microRNA (miRNA) biogenesis through interactions with the DROSHA and DICER complexes. It has been previously shown that there is a general reduction in miRNA levels within the spinal cord and spinal motor neurons of amyotrophic lateral sclerosis (ALS) patients. In addition, the most common pathological feature of ALS is re-distribution of TDP-43 from the nucleus to the cytoplasm where it forms cytoplasmic inclusions. Among miRNAs dysregulated in ALS, several are known to regulate TDP-43 expression. In this study, we demonstrate that TDP-43 is in a regulatory negative feedback network with miR-181c-5p and miR-27b-3p that is dependent on its nuclear localization within HEK293T cells. Further, we show that cellular stress which induces a redistribution of TDP-43 from the nucleus to the cytoplasm correlates with the reduced production of miR-27b-3p and miR-181c-5p. This suggests that reduced nuclear TDP-43 disrupts a negative feedback network between itself and miRNAs. These findings provide a further understanding of altered miRNA biogenesis as a key pathogenic process in ALS.