Interplay between vascular hemodynamics and the glymphatic system in the pathogenesis of idiopathic normal pressure hydrocephalus, exploring novel neuroimaging diagnostics.

As the aging population continues to grow, so will the incidence of age-related conditions, including idiopathic normal pressure hydrocephalus (iNPH). The pathogenesis of iNPH remains elusive, and this is due in part to the poor characterization of cerebral spinal fluid (CSF) dynamics within the brain. Advancements in technology and imaging techniques have enabled new breakthroughs in understanding CSF physiology, and therefore iNPH pathogenesis. This includes understanding the hemodynamic and microvascular components involved in CSF influx and flow. Namely, the glymphatic system appears to be the great mediator, facilitating perivascular CSF flow via astrocytic aquaporin channels located along the endothelium of the pial vasculature. The interplay between glymphatics and both arterial pulsatilty and venous compliance has also been recently demonstrated. It appears then that CSF flow, and therefore glymphatic function, are highly dependent on cardiocirculatory and vascular factors. Impairment in any one component, whether it be related to arterial pulsatility, microvascular changes, reduced venous drainage, or astrogliosis, contributes greatly to iNPH, although it is likely a combination thereof. The strong interplay between vascular hemodynamics and CSF flow suggests perfusion imaging and cerebral blood flow quantification may be a useful diagnostic tool in characterizing iNPH. In addition, studies detecting glymphatic flow with magnetic resonance imaging have also emerged. These imaging tools may serve to both diagnose iNPH and help delineate it from other similarly presenting disease processes. With a better understanding of the vascular and glymphatic factors related to iNPH pathogenesis, physicians are better able to select the best candidates for treatment.

Microglia Modulate Cortical Spreading Depolarizations After Ischemic Stroke: A Narrative Review.

Cortical spreading depolarizations (CSDs) are characterized by waves of diminished electroencephalography activity that propagate across the cortex with subsequent loss of ionic homeostasis. CSDs have been found in many pathological conditions, including migraine, traumatic brain injury, and ischemic stroke. Because of CSD-associated ionic and metabolic disturbances at the peri-infarct area after ischemic stroke, it is thought that CSDs exacerbate tissue infarction and worsen clinical outcomes. Microglia, the main innate immune cells in the brain, are among the first responders to brain tissue damage. Recent studies demonstrated that microglia play a critical role in CSD initiation and propagation. In this article, we discuss the significance of CSD in the setting of ischemic stroke and how microglia may modulate peri-infarct CSDs, also known as iso-electric depolarizations. Finally, we discuss the significance of microglial Ca2+ and how it might be used as a potential therapeutic target for patients with ischemic stroke.

Largest neurosurgical social media group and its impact on communication and research.

BACKGROUND: The use of social media to communicate and disseminate knowledge has increased exponentially, especially in the field of neurosurgery. 'Neurosurgery cocktail' (NC) was developed by a group of young neurosurgeons as a means of sharing didactic materials and clinical experiences via social media. It connects 35.000 neurosurgeons worldwide on multiple platforms, primarily Facebook and Twitter. Given the rising utilization of social media in neurosurgery, the popularity of NC has also increased since its inception. In this study, the authors surveyed the social media analytics of NC for both Facebook and Twitter. Besides, we reviewed the literature on the use of social media in neurosurgery. METHODS: Facebook and Twitter metrics were extracted through each respective platform's analytics tools from December 2020 (earliest available date for data analysis) through January 2021. A literature search was conducted using PubMed (MEDLINE) and Scopus databases. RESULTS: On Facebook, as of January 2021, the group had a total of 25.590 members (87.6% male), most commonly (29%) between 35 and 44 years of age with over 100 countries were represented. As of January 2021, they had amassed 6457 followers on Twitter. During the last 28 d between December 2020 and January 2021, the account published 65 tweets that garnered a total of 196,900 impressions. Twelve articles were identified in our literature review on the use of social media within the neurosurgical community. CONCLUSIONS: NC is one of the most widely utilized neurosurgical social media resources available. Sharing knowledge has been broadened thanks to the recent social media evolution, and NC has become a leading player in disseminating neurosurgical knowledge.

Microglial Calcium Waves During the Hyperacute Phase of Ischemic Stroke.

BACKGROUND AND PURPOSE: Ischemic injury triggers multiple pathological responses in the brain tissue, including spreading depolarizations across the cerebral cortex (cortical spreading depolarizations [CSD]). Microglia have been recently shown to play a significant role in the propagation of CSD. However, the intracellular responses of myeloid cells during ischemic stroke have not been investigated. METHODS: We have studied intracellular calcium activity in cortical microglia in the stroke model of the middle cerebral artery occlusion, using the murine Polr2a-based and Cre-dependent GCaMP5 and tdTomato reporter (PC::G5-tdT). High-speed 2-photon microscopy through cranial windows was employed to record signals from genetically encoded indicators of calcium. Inflammatory stimuli and pharmacological inhibition were used to modulate microglial calcium responses in the somatosensory cortex. RESULTS: In vivo imaging revealed periodical calcium activity in microglia during the hyperacute phase of ischemic stroke. This activity was more frequent during the first 6 hours after occlusion, but the amplitudes of calcium transients became larger at later time points. Consistent with CSD nature of these events, we reproducibly triggered comparable calcium transients with microinjections of potassium chloride (KCl) into adjacent cortical areas. Furthermore, lipopolysaccharide-induced peripheral inflammation, mimicking sterile inflammation during ischemic stroke, produced significantly greater microglial calcium transients during CSD. Finally, in vivo pharmacological analysis with CRAC (calcium release-activated channel) inhibitor CM-EX-137 demonstrated that CSD-associated microglial calcium transients after KCl microinjections are mediated at least in part by the CRAC mechanism. CONCLUSIONS: Our findings demonstrate that microglia participate in ischemic brain injury via previously undetected mechanisms, which may provide new avenues for therapeutic interventions.

Three-dimensional printing and craniosynostosis surgery.

OVERVIEW: The goal of this study was to review the current application and status of three-dimensional printing for craniosynostosis surgery. METHODS: A literature review was performed using the PubMed/MEDLINE databases for studies published between 2010 and 2020. All studies demonstrating the utilization of three-dimensional printing for craniosynostosis surgery were included. RESULTS: A total of 15 studies were ultimately selected. This includes studies demonstrating novel three-dimensional simulation and printing workflows, studies utilizing three-dimensional printing for surgical simulation, as well as case reports describing prior experiences. CONCLUSION: The incorporation of three-dimensional printing into the domain of craniosynostosis surgery has many potential benefits. This includes streamlining surgical planning, developing patient-specific template guides, enhancing residency training, as well as aiding in patient counseling. However, the current state of the literature remains in the validation stage. Further study with larger case series, direct comparisons with control groups, and prolonged follow-up times is necessary before more widespread implementation is justified.

Arteriovenous malformation presenting with epilepsy: a multimodal approach to diagnosis and treatment.

Arteriovenous malformation (AVM) presenting with epilepsy significantly impacts patient quality of life, and it should be considered very much a seizure disorder. Although hemorrhage prevention is the primary treatment aim of AVM surgery, seizure control should also be at the forefront of therapeutic management. Several hemodynamic and morphological characteristics of AVM have been identified to be associated with seizure presentation. This includes increased AVM flow, presence of long pial draining vein, venous outflow obstruction, and frontotemporal location, among other aspects. With the advent of high-throughput image processing and quantification methods, new radiographic attributes of AVM-related epilepsy have been identified. With respect to therapy, several treatment approaches are available, including conservative management or interventional modalities; this includes microsurgery, radiosurgery, and embolization or a combination thereof. Many studies, especially in the domain of microsurgery and radiosurgery, evaluate both techniques with respect to seizure outcomes. The advantage of microsurgery lies in superior AVM obliteration rates and swift seizure response. In addition, by incorporating electrophysiological monitoring during AVM resection, adjacent or even remote epileptogenic foci can be identified, leading to extended lesionectomy and improved seizure control. Radiosurgery, despite resulting in reduced AVM obliteration and prolonged time to seizure freedom, avoids the risks of surgery altogether and may provide seizure control through various antiepileptic mechanisms. Embolization continues to be used as an adjuvant for both microsurgery and radiosurgery. In this study, the authors review the latest imaging techniques in characterizing AVM-related epilepsy, in addition to reviewing each treatment modality.

A systematic review of endovascular stent-electrode arrays, a minimally invasive approach to brain-machine interfaces.

OBJECTIVE: The goal of this study was to systematically review the feasibility and safety of minimally invasive neurovascular approaches to brain-machine interfaces (BMIs). METHODS: A systematic literature review was performed using the PubMed database for studies published between 1986 and 2019. All studies assessing endovascular neural interfaces were included. Additional studies were selected based on review of references of selected articles and review articles. RESULTS: Of the 53 total articles identified in the original literature search, 12 studies were ultimately selected. An additional 10 articles were included from other sources, resulting in a total of 22 studies included in this systematic review. This includes primarily preclinical studies comparing endovascular electrode recordings with subdural and epidural electrodes, as well as studies evaluating stent-electrode gauge and material type. In addition, several clinical studies are also included. CONCLUSIONS: Endovascular stent-electrode arrays provide a minimally invasive approach to BMIs. Stent-electrode placement has been shown to be both efficacious and safe, although further data are necessary to draw comparisons between subdural and epidural electrode measurements given the heterogeneity of the studies included. Greater access to deep-seated brain regions is now more feasible with stent-electrode arrays; however, further validation is needed in large clinical trials to optimize this neural interface. This includes the determination of ideal electrode material type, venous versus arterial approaches, the feasibility of deep brain stimulation, and more streamlined computational decoding techniques.

Endoscopic endonasal surgery outcomes for pediatric craniopharyngioma: a systematic review.

OBJECTIVE: The goal of this study was to systematically review the outcomes of endoscopic endonasal surgery (EES) for pediatric craniopharyngiomas so as to assess its safety and efficacy. METHODS: A systematic literature review was performed using the PubMed and MEDLINE databases for studies published between 1986 and 2019. All studies assessing outcomes following EES for pediatric craniopharyngiomas were included. RESULTS: Of the total 48 articles identified in the original literature search, 13 studies were ultimately selected. This includes comparative studies with other surgical approaches, retrospective cohort studies, and case series. CONCLUSIONS: EES for pediatric craniopharyngiomas is a safe and efficacious alternative to other surgical approaches. Achieving gross-total resection with minimal complications is feasible with EES and is comparable, if not superior in some cases, to traditional means of resection. Ideally, a randomized controlled trial might be implemented in the future to further elucidate the effectiveness of EES for resection of craniopharyngiomas.

Chiari I malformation in children-the natural history.

PURPOSE: To review the natural history of asymptomatic and symptomatic pediatric Chiari I malformations with and without syringomyelia. MATERIALS AND METHODS: We reviewed the literature for case reports and case series describing the natural history of asymptomatic and symptomatic children with Chiari I malformations with and without syringomyelia. Our review included approximately 700 asymptomatic children without syringomyelia, 100 symptomatic children without syringomyelia, 22 asymptomatic children with syringomyelia, and 11 symptomatic children with syringomyelia. Symptomatic and imaging outcomes at the point of last reported follow-up were noted to describe the natural history of Chiari I malformations in children. RESULTS: Our review of about 700 asymptomatic children with CM-I without syrinx revealed that most children do not exhibit new-onset symptoms (5-6%) or syrinx (2-3%). The nearly 100 published cases of symptomatic CM-I without syrinx suggest that about half of children report symptomatic improvement (48%) and few report symptomatic worsening (7%). New-onset syrinx is rarely observed (2%). Few cases have been published about asymptomatic and symptomatic CM-I with syrinx as syringomyelia are generally regarded to be an indication for surgical intervention. Nevertheless, all 22 children with asymptomatic CM-I with syringomyelia included in this study were asymptomatic at follow-up, with syrinx resolution observed in 18 children and tonsillar herniation improvement observed in 16 children. Overall, our review of asymptomatic pediatric CM-I with or without syringomyelia suggests that its natural history is much more favorable than previously acknowledged and that the literature generally favors conservative management of these cases. CONCLUSION: Our review of asymptomatic pediatric CM-I with or without syringomyelia suggests that its natural history is much more favorable than previously acknowledged and that the literature generally favors conservative management of these cases. Further study of symptomatic pediatric CM-I is necessary to better understand its natural history.

Enhanced recovery after surgery in intramedullary and extramedullary spinal cord lesions: perioperative considerations and recommendations.

Enhanced recovery after surgery (ERAS) is an evidence-based approach developed to ameliorate the patient recovery process following surgical procedures. Employing a multimodal, multidisciplinary approach, ERAS implements strategies and treatment paradigms that have been shown to improve patient outcomes, reduce hospital length of stay, and ultimately reduce healthcare costs. With a substantial body of the literature supporting the implementation of ERAS in other surgical specialties, ERAS has only recently made its foray into spine surgery. Despite this, current studies are limited to spinal deformity and degenerative disease, with limited data regarding spinal cord surgery. This is due in part to the complex nature and rarity of spinal cord lesions, making the establishment of a formal ERAS protocol difficult. In developing an ERAS protocol, there must be a consensus on what factors are important to consider and implement. To address this, we reviewed the most recent advances in intramedullary and extramedullary spinal cord surgery in order to identify elements that influence patient outcomes. Using this information, the authors provide evidence-based recommendations with the intent of introducing a framework for future ERAS protocols with respect to treating spinal cord lesions.

Enhanced recovery after spine surgery: a systematic review.

OBJECTIVEEnhanced recovery after surgery (ERAS) is a multidimensional approach to improving the care of surgical patients using subspecialty- and procedure-specific evidence-based protocols. The literature provides evidence of the benefits of ERAS implementation, which include expedited functional recovery, decreased postoperative morbidity, reduced costs, and improved subjective patient experience. Although extensively examined in other surgical areas, ERAS principles have been applied to spine surgery only in recent years. The authors examine studies investigating the application of ERAS programs to patients undergoing spine surgery.METHODSThe authors conducted a systematic review of the PubMed and MEDLINE databases up to November 20, 2018.RESULTSTwenty full-text articles were included in the qualitative analysis. The majority of studies were retrospective reviews of nonrandomized data sets or qualitative investigations lacking formal control groups; there was 1 protocol for a future randomized controlled trial. Most studies demonstrated reduced lengths of stay and no increase in rates of readmissions or complications after introduction of an ERAS pathway.CONCLUSIONSThese introductory studies demonstrate the potential of ERAS protocols, when applied to spine procedures, to reduce lengths of stay, accelerate return of function, minimize postoperative pain, and save costs.

Extracranial-intracranial bypass approach to cerebral revascularization: a historical perspective.

While the majority of cerebral revascularization advancements were made in the last century, it is worth noting the humble beginnings of vascular surgery throughout history to appreciate its progression and application to neurovascular pathology in the modern era. Nearly 5000 years of basic human inquiry into the vasculature and its role in neurological disease has resulted in the complex neurosurgical procedures used today to save and improve lives. This paper explores the story of the extracranial-intracranial approach to cerebral revascularization.

Clinical utility of arterial spin labeling imaging in disorders of the nervous system.

Neuroimaging is an indispensable tool in the workup and management of patients with neurological disorders. Arterial spin labeling (ASL) is an imaging modality that permits the examination of blood flow and perfusion without the need for contrast injection. Noninvasive in nature, ASL provides a feasible alternative to existing vascular imaging techniques, including angiography and perfusion imaging. While promising, ASL has yet to be fully incorporated into the diagnosis and management of neurological disorders. This article presents a review of the most recent literature on ASL, with a special focus on its use in moyamoya disease, brain neoplasms, seizures, and migraines and a commentary on recent advances in ASL that make the imaging technique more attractive as a clinically useful tool.

The biophysical role of hemodynamics in the pathogenesis of cerebral aneurysm formation and rupture.

The pathogenesis of intracranial aneurysms remains complex and multifactorial. While vascular, genetic, and epidemiological factors play a role, nascent aneurysm formation is believed to be induced by hemodynamic forces. Hemodynamic stresses and vascular insults lead to additional aneurysm and vessel remodeling. Advanced imaging techniques allow us to better define the roles of aneurysm and vessel morphology and hemodynamic parameters, such as wall shear stress, oscillatory shear index, and patterns of flow on aneurysm formation, growth, and rupture. While a complete understanding of the interplay between these hemodynamic variables remains elusive, the authors review the efforts that have been made over the past several decades in an attempt to elucidate the physical and biological interactions that govern aneurysm pathophysiology. Furthermore, the current clinical utility of hemodynamics in predicting aneurysm rupture is discussed.

Evaluation of the Safety of Liberalized Systolic Blood Pressure Goals in the Postoperative Period After Intracranial Tumor Resection.

BACKGROUND AND OBJECTIVES: Postoperative intracranial hemorrhage (POH) is a serious neurosurgical complication occurring in approximately 1.4% of patients after intracranial tumor resection. The convention across the United States is to maintain an immediate postoperative systolic blood pressure (SBP) of < 140 mm Hg to minimize this risk; however, this SBP goal lacks support in the literature despite widespread adoption. This study aims to investigate the safety of SBP liberalization to 160 mm Hg in the immediate postoperative setting after intracranial tumor resection. METHODS: A retrospective review was conducted on consecutive patients, aged 18 to 75 years, undergoing craniotomy for intracranial tumor resection from October 2020 until June 2023. Data were gathered from the electronic medical record per Institutional Review Board guidelines regarding demographics, operative details, perioperative vital signs, resource utilization, and complications. Pharmaceutical prices and insurance charges were approximated from costs provided by the institution's pharmacy. POH was defined as symptomatic hemorrhage within 48 hours requiring intervention. RESULTS: The study included 147 patients, with 104 in the liberalized cohort (SBP <160 mm Hg) and 43 in the standard cohort (SBP <140 mm Hg). The average age was 54.5 ± 14.9 years and 57.6 ± 10.6 years in the liberalized and standard groups, respectively (P = .23). Intensive care unit and hospital length of stay were not significantly different between groups. The liberalized group used $81.88 ± $280.19 (95% CI $53.01-$110.75) on as-needed antihypertensive medications vs $108.39 ± $215.91 (95% CI $75.96-$140.82) in the standard (P = .29), with significantly lower labetalol (P = .04). There was no POH in either cohort. CONCLUSION: Liberalization of SBP goals to <160 mm Hg appears safe in the immediate postoperative period after craniotomy for tumor resection without an increased POH risk. Liberalized SBP parameters may allow reduced antihypertensive medication usage, thereby avoiding excess hospital cost and medication side effects.

High-Volume Centers Provide Superior Value of Care in the Surgical Treatment of Malignant Brain Tumor.

BACKGROUND: Improved outcomes in surgical patients have been associated with increasing volume of cases. This has led to the development of centers that facilitate care for a specific patient population. This study aimed to evaluate associations of outcomes with hospital characteristics in patients undergoing resection of malignant brain tumors. METHODS: The 2016-2020 National Inpatient Sample was queried for patients undergoing resection of malignant brain tumors. Teaching hospitals with caseloads >2 standard deviations above the mean (140 cases) were categorized as high-volume centers (HVCs). Value of care was evaluated by adding one point for each of the following: short length of stay, low total charges, favorable discharge disposition, and lack of major comorbidity or complication. RESULTS: In 3009 hospitals, 118,390 patients underwent resection of malignant brain tumors. HVC criteria were met by 91 (3%) hospitals. HVCs were more likely to treat patients of younger age or higher socioeconomic status (P < 0.01 for all). The Mid-Atlantic and South Atlantic regions had the highest percentage of cases and number of HVCs. Value of care was higher at HVCs (P < 0.01). Care at HVCs was associated with decreased complications (P < 0.01 for all) and improved patient outcomes (P < 0.01 for all). CONCLUSIONS: Patients undergoing craniotomy for malignant brain neoplasms have superior outcomes in HVCs. Trends of centralization may reflect the benefits of multidisciplinary treatment, geographic preferences, publicity, and cultural impact. Improvement of access to care is an important consideration as this trend continues.

Pediatric Patients with Intracranial Arteriovenous Malformations: Trends in Emergency Room Presentation.

BACKGROUND: Pediatric intracranial arteriovenous malformation (AVM) patients are commonly admitted to the emergency room (ER). Increasing patient utilization of the ER has been associated with healthcare disparities and a trend of decreased efficiency. The aim of this study was to evaluate the trends of pediatric AVM ER admissions over recent years and identify factors associated with health care resource utilization and outcomes. METHODS: The 2016-2019 National Inpatient Sample was queried for patients under the age of 18 admitted with AVM. Cases of admission through the ER were identified. Demographic and severity factors associated with ER admission were explored using comparative and regression statistics. RESULTS: Of 3875 pediatric patients with AVM admitted between 2016 and 2019, 1280 (33.0%) were admitted via the ER. Patients admitted via the ER were more likely to be in the lowest median income category (P < 0.001), on Medicaid insurance (P = 0.008), or in the South (P < 0.001) than patients admitted otherwise. There was increased severity and increased rates of intracranial hemorrhage (ICH) in patients admitted via the ER (P < 0.001). Finally, there were increasing trends in ER admissions and ICH throughout the years. CONCLUSIONS: ER admission of pediatric AVM patients with ICH is increasing and is associated with a distinct socioeconomic profile and increased healthcare resource utilization. These findings may reflect decreased access to more advanced diagnostic modalities, primary care, and other important resources. Identifying populations with barriers to care is likely an important component of policy aimed at decreasing the risk of severe disease presentation.

Exploring the dynamics of adult Axin2 cell lineage integration into dentate gyrus granule neurons.

The Wnt pathway plays critical roles in neurogenesis. The expression of Axin2 is induced by Wnt/ß-catenin signaling, making this gene a reliable indicator of canonical Wnt activity. We employed pulse-chase genetic lineage tracing with the Axin2-CreERT2 allele to follow the fate of Axin2+ lineage in the adult hippocampal formation. We found Axin2 expressed in astrocytes, neurons and endothelial cells, as well as in the choroid plexus epithelia. Simultaneously with the induction of Axin2 fate mapping by tamoxifen, we marked the dividing cells with 5-ethynyl-2'-deoxyuridine (EdU). Tamoxifen induction led to a significant increase in labeled dentate gyrus granule cells three months later. However, none of these neurons showed any EdU signal. Conversely, six months after the pulse-chase labeling with tamoxifen/EdU, we identified granule neurons that were positive for both EdU and tdTomato lineage tracer in each animal. Our data indicates that Axin2 is expressed at multiple stages of adult granule neuron differentiation. Furthermore, these findings suggest that the integration process of adult-born neurons from specific cell lineages may require more time than previously thought.

Percutaneous Direct Pars Repair in Young Athletes.

BACKGROUND: Lumbar pars defects are common in adolescent athletes and are often due to recurrent axial loading and traumatic stressors. OBJECTIVE: To present an updated case series of young athletes who underwent percutaneous direct pars repair after failure of conservative management. METHODS: A single-center, nonrandomized, retrospective observation study of athletes who were referred for minimally invasive direct pars repair after failure of at least 6 months of conservative management was performed. Summary demographic information, clinical features of presentation, perioperative and intraoperative radiographic imaging, and visual analog scale back pain scores were collected and analyzed. RESULTS: A total of 21 patients were included (mean age [± SD] 17.47 ± 3.02 years, range 14-25 years), 6 of whom were female (29%). All patients presented with bilateral pars fractures, with L5 being the most frequent level involved (n = 13). The average follow-up time was 31.52 ± 9.38 months (range 3-110 months). The visual analog scale score for back pain was significantly reduced from 7.62 ± 1.83 preoperatively to 0.28 ± 0.56 at the final postoperative examination (P < .01). Fusion was noted in 20 of the 21 patients on final follow-up (95%). CONCLUSION: Percutaneous direct pars repair is a safe and effective means in treating young adolescents who have failed conservative management. The advantages included minimized muscle and soft tissue dissection, reduced blood loss, and early mobilization and recovery. In young athletes who desire return to high-level physical activity, this surgical technique is of particular benefit and should be considered in this patient population.

Surgical Management of Lumbosacral Plexus Tumors.

BACKGROUND: Lumbosacral plexus tumors are uncommon, and because of their deep location and proximity to critical nerves subserving lower extremity function, understanding surgical approaches and short-term outcomes is important. METHODS: In a retrospective case series of lumbosacral plexus tumor surgeries performed from May 2000 to July 2021 by a single neurosurgeon, demographic information, clinical presentation, imaging studies, and operative outcomes were analyzed. RESULTS: A total of 42 patients with mean age of 48.3 years (range, 16-84 years) underwent surgery for a lumbosacral plexus tumor. Patients presented with leg pain (n = 25; 59.5%), followed by back/flank pain (n = 5; 11.9%), abdominal/pelvic pain (n = 5; 11.9%), leg weakness (n = 5; 11.9%), and leg numbness (n = 3; 7.1%). The most common tumor pathology was schwannoma (n = 20; 50.0%) followed by neurofibroma (n = 9; 22.5%). A retroperitoneal approach was used in all cases. Gross total resection was achieved in 23 (54.8%) patients, and only 1 (2.4%) patient exhibited symptomatic tumor recurrence after subtotal resection of a malignant tumor. Mean follow-up was 33.1 months (range, 1-96 months). Postoperatively, patient neurological status remained unchanged or improved (n = 37; 88.1%). Complications were infrequent, with 4 (9.5%) patients experiencing new sensory symptoms and 1 patient (2.4%) experiencing new anticipated motor weakness after en bloc resection of a malignant tumor. CONCLUSIONS: Indications for surgery include pain and/or neurological symptoms attributable to the lesion or large size if asymptomatic. Careful study of preoperative imaging is necessary to determine the best approach. Intraoperative nerve stimulation is essential to preserve function and guide extent of resection in benign tumors.