Issue Of Neurosurgical Focus Research Articles

Complications: skull base and cerebrovascular

Neurosurgical complications are a rich source for learning, but they are grossly underutilized for the purpose of surgeon education. Details of the complications, which make them all the more powerful as teaching tools, are restricted to morbidity and mortality conferences behind closed doors, and open discussions of the topic are blurred by hypotheticals in order to shield the presenters from medicolegal risks. In this issue of Neurosurgical Focus, 9 neurosurgeons were invited to present complications they encountered along with the details and specific lessons they learned. The contributors were picked for their well-known track record of skill, experience, and candor, so readers can be confident in the lessons. The video and the accompanying written article present the clinical facts. The actions that led to the complications are demonstrated in the surgical video segments. In ancient Western civilization, the seven "deadly sins" categorized and conceptualized human malfeasance, and similarly, the neurosurgical correlate of this set of sins can provide a framework for discussing the errors that lead to unexpectedly poor outcomes. Although errors in judgment and planning grow rarer with experience, errors in execution can still occur, no matter the stage of one’s career. Interestingly, even though skill and experience do not eliminate complications, they may affect the lesson that the neurosurgeon takes home. The lack of open discourse on complications may slow progress in the field and set the stage for repeating mistakes. The writing and production teams hope that this work opens a rich source of learning. The video can be found here: https://stream.cadmore.media/r10.3171/2024.7.FOCUS24379

Introduction. Expanding lateral access spine surgery

Lateral approaches to the spine have been increasingly recognized as a minimally invasive way to treat spinal pathology and improve patient outcomes. Even as the number of spine cases using the lateral approach increases internationally, many spine surgeons are reticent to adopt lateral approaches as they may have not had exposure to these techniques in their training. Furthermore, if this training did occur, it may have been limited to more straightforward degenerative lateral techniques at the midlumbar levels, and thus for these surgeons more advanced lateral techniques may remain daunting. In this issue of Neurosurgical Focus: Video

Introduction. Immunology of neurosurgical diseases.

Neuroimmunology first emerged as an independent discipline early in the 1980s. Initially, the brain was regarded as an immune-privileged site, as the blood-brain barrier prevented immune access. To our benefit, the field of immunology evolved significantly, and, 40 years from its inception, neuroimmunology has proven that these two systems are closely intertwined. Over the years, we have garnered a vast improvement in the understanding of the intricate crosstalk and mechanistic insights between the immune system and the central nervous system.This issue of Neurosurgical Focus on neuroimmunology aims to describe the most recent developments in immunology

Introduction: microsurgical and endovascular management of intracranial dural arteriovenous fistula

Over the past decade substantial advances in diagnostic imaging, classification, and understanding the natural history of intracranial dural arteriovenous fistula (dAVF) have been made. Paralleling these improvements in patient evaluation and risk assessment have been considerable innovations and refinements in the microsurgical and endovascular techniques by which appropriately selected patients with dAVF are treated. On the microsurgical front, minimally invasive surgical approaches with less soft tissue and bony disruption, along with enhanced tools for the intraoperative assessment of vascular anatomy and completeness of dAVF obliteration, are now commonly utilized. On the endovascular front, liquid embolic agents, balloons, and flow-directed catheters have transformed our capacity to safely and effectively treat dAVFs with a variety of anatomic configurations and locations. Innovative combinations of microsurgical and endovascular approaches are even being applied to select cases. In this issue of Neurosurgical Focus, we present a series of narrated videos that demonstrate the decision-making, vascular anatomy, and technical nuances of many of these advanced techniques, while also providing narrated videos demonstrating tried-and-true microsurgical and endovascular approaches that have proven highly effective over the years. We hope this video supplement provides a meaningful update and demonstration of modern microsurgical and endovascular approaches to patients with dAVF and aids all of us in our unending quest to provide even better care for our patients in the future. We thank the authors for their outstanding contributions.

Introduction: Endovascular Neurosurgery.

Remarkable developments in the field of endovascular neurosurgery have been witnessed in the last decade. The success of endovascular therapy for ischemic stroke treatment is now irrefutable, making it an accepted standard of care. Endovascular treatment of cerebral aneurysms is no longer limited to primary coiling but now includes options such as stent or balloon assistance and flow diversion and applications utilizing neck reconstruction, intrasaccular, and bifurcation-specific devices. Balloons, liquid embolic agents, and flow-directed catheters have revolutionized the treatment of arteriovenous malformations and fistulae. The ongoing development of endovascular tools has led to novel and expanding approaches (for example, transvenous arteriovenous malformation embolization and transradial access). With improved technology, transposterior communicating artery access and other endovascular strategies are being applied successfully across the anterior and posterior circulations and to lesions once deemed only surgically approachable. Yet, we would be remiss to attribute the successes of endovascular strategies only to the development of their tools. Improvements in both noninvasive and angiographic imaging (such as three-dimensional road map guidance) have provided a greater understanding of pathologic entities and allowed the pursuit of endovascular cures.In this issue of Neurosurgical Focus, we present a wide range of endovascular strategies for a variety of neurovascular pathologies. We hope this video supplement will not only demonstrate the applicability of tried-and-true endovascular strategies to difficult clinical situations but also highlight new and developing endovascular technologies. We thank the authors for their outstanding contributions.

Introduction: the rise of the robots in spinal surgery.

In his 1920 science fiction play R.U.R., Czech writer Karel Capek introduced the word "robot" to the English language. The play tells the story of a factory that produces roboti, which are living creatures that resemble humans and have the capacity for individual thought. While at first the roboti seem content to work for their human masters, they later rebel, ultimately leading to the extinction of the human race. 1 This play and similar depictions of robots in literature and film are probably responsible for the slightly negative reputation of robots in general. Only recently has this perception changed, thanks to the advent of robots that can vacuum our houses and perform other mundane chores. Raymond Goertz, while working for the US Atomic Energy Commission, is credited with the development of the first robotic arm in 1951. 2 It was designed to handle hazardous radioactive material. Unimation Inc. developed the first industrial robot in 1961; that robot handled molten die-castings and removed the human element from these labor-intensive, often dangerous tasks. With the development of the Programmable Universal Manipulation Arm (PUMA) in 1978, the robot was sophisticated enough to be introduced to medicine. The first working definition of the word "robot" was published, fittingly, by the Robotics Institute of America in 1980: ". . . a reprogrammable, multifunctional manipulator designed to move materials, parts, tools, or specialized devices through various programmed motions for the performance of a variety of tasks." 6 In 1988, the six-degrees-of-freedom flexible arm PUMA 560 was used to guide a needle under CT guidance into the brain. 4 With the introduction of robotic arms came the ability to use them as surgical assistants. In 1998, Okada et al. described a voice-controlled robot used to hold a thoracoscope. 5 This type of robot was also used in thoracoscopic spinal surgery. The military, having a vested interest in telepresence surgery, helped fund the development of the da Vinci Surgical System that was approved for use by the FDA in 2000 and designed to facilitate complex, minimally invasive intracavitary surgeries. 7 In 2004, the FDA cleared the first commercially available positioning device for the placement of spinal instrumentation. At present, several systems are commercially available that utilize robotics for spinal operations. In a recent review, Joseph et al. evaluated the current landscape regarding safety, accuracy, and radiation exposure with the use of these technologies. These authors concluded that "… the placement of pedicle screws with robotics appears to be safe, and accuracy appears to be superior to freehand placement, although the data are not conclusive." 3 There seems to be a significant level of interest in this technology; however, only time will tell if it will become commonplace in our field. In this issue of Neurosurgical Focus, we visually explore the expanding role of robotics and image guidance in spinal surgery. New robots used for the first time and existing robots used for novel applications graphically demonstrate how our field is evolving. The days of fearing robots are behind us as members of our specialty begin to embrace the concept of automation. Thankfully, unlike Capek's rogue roboti, surgical robots rising up against us and causing world destruction is unlikely!

Robotic approach for mediastinal lesions: the surgery of extreme locations

In the recent issue of Neurosurgical Focus, Pacchiarotti et al. described their experience with robotic resection of paravertebral tumors, particularly focusing on the extreme locations into the thorax, as the superior and the inferior sulci (1).

Introduction: Glioblastoma: an update on pathophysiology and management strategies.

Glioblastoma multiforme remains an enigma for neu­ rooncology; our understanding has progressed, but the prognosis is still poor. In this issue of Neurosurgical Focus, the emphasis is on presenting current understanding of the pathophysiology of the disease and the manage­ ment strategies that stem from it. The issue can be divided into current management strategies and future treatments based on recent advances in understanding glioblastoma pathophysiology, including cancer stem cells, angiogen­ esis, and tumor heterogeneity. The first part of the issue is devoted to an evaluation of treatment methods available to patients today. From an operative standpoint, Hawasli et al. present a timely ar­ ticle on the use of stereotactic laser ablation of high­grade gliomas, a procedure that is available to most neurosur­ geons using the current armamentarium of imaging and ablative equipment. Lescher and colleagues assert that the time frame for the evaluation of postoperative chang­ es versus residual tumor is important in determining the extent of resection, given increasing data showing sur­ vival benefits with radiographically grossor near-total resections. From a medical perspective, Barbagallo et al. report data on long­term treatment with temozolomide, whereas Pompili et al. describe palliative care and end of life issues for patients with glioblastoma. The second part of this issue emphasizes the role of future treatments that will stem from recent advances in understanding the pathophysiology of glioblastoma mul­ tiforme. Sundar et al. present a timely review on the role of cancer stem cells in glioblastoma, which is followed by Khan and Ehtesham’s article on treatment based on targeting glioma stem cells. The importance and role of angiogenesis in glioblastoma pathophysiology is demon­ strated in Womeldorff et al.’s article on the role of hy­ poxia­inducible factor­1, hypoxia, and cytokine­induced angiogenesis. Understanding the role of angiogenesis leads to a better evaluation of the role of bevacizumab in glioblastoma treatment (Castro and Aghi) and the role of MET activation as a reaction to its use (Awad et al.). Tumor heterogeneity and the microenvironment are well recognized in glioblastoma, but recent advances in mo­ lecular genomics enable not only a precise diagnosis, but also prognostic implications. Aum et al. present a pre­ cise overview of the molecular and cellular heterogene­ ity found in glioblastoma. Golden et al. report preclinical data on the role of chloroquine and autophagy in glioblas­ toma. Two genes with important prognostic implications have recently been identified: IDH (Agnihotri et al.) and WT1 (Broaddus et al.). Identification of these targets can lead to new molecularly targeted therapies (Lau et al.). Treatment of glioblastoma requires a multidisciplin­ ary approach based on understanding the pathophysiol­ ogy of the disease, which will eventually lead to a better prognosis and quality of life for our patients. (http://thejns.org/doi/abs/10.3171/2014.9.FOCUS14677)

Introduction: vertebral osteomyelitis and spinal epidural abscess.

Infections of the vertebral column can result in ver­ tebral osteomyelitis with or without epidural abscess. Moreover, spontaneous infection arising from the epidu­ ral space can occur, leading to epidural abscess. Whether these infections arise spontaneously or postoperatively, they can progress rapidly and cause severe neurologi­ cal deficits. Despite the wide availability of intravenous antibiotics and advanced surgical techniques in recent decades, vertebral osteomyelitis and epidural abscess re­ main problematic and are major causes of debilitating neurological injury and morbidity. Appropriate treat­ ment of vertebral osteomyelitis and epidural abscess is essential to prevent calamitous consequences, including paralysis and death. Physicians and practitioners should first be aware of the natural history and risk factors associated with these diseases to perform appropriate diagnostic modalities. Speedy and accurate diagnosis is the first essential step to direct timely treatments. Although vertebral osteomyelitis and epidural abscess are considered to be rare historically, their incidence appears to be increasing in recent years compared with that in the first half of the 20th century.2 This disparity in epidemiology results from a number of factors, including improved neuroimaging capabilities, better awareness of these diseases, an increased number of elderly individuals, and a greater number of immuno­ compromised patients, from cancer survivors to individu­ als with human immunodeficiency virus (HIV) infection. At the same time, there is a growing rate of illicit drug abuse in the United States as well as a greater incidence of methicillin­resistant Staphylococcus aureus infections. Despite having sophisticated imaging techniques and labo­ ratory studies, the rate of misdiagnosis at presentation for vertebral osteomyelitis and epidural abscess is still high, with an average rate of approximately 50%.3,5,7 Symptomatic vertebral osteomyelitis and epidural abscess with neurological deficits have long been con­ sidered surgical emergencies. The goal of surgery is to provide direct decompression of spinal cord and nerves to prevent neurological deterioration and reverse neu­ rological deficits. Since local inflammation leading to thrombophlebitis or venous congestion is thought to be the mechanism of neurological injury in some cases, sur­ gical debridement can also remove the inciting organisms and factors to reduce the risk of vascular­related neuro­ logical complications. On the other hand, the treatment of neurologically intact patients with vertebral osteomyelitis alone or minimal epidural abscess is quite controversial. Successful medical treatment for these types of cases has been reported, as have cases of failed medical treat­ ment resulting in neurological decline.1,3,4,6,8 The scarcity of these cases along with the wide variation in clinical presentations makes it difficult to conduct any largescale observational studies. Furthermore, conducting a randomized study of treatment in these diseases raises ethical concerns because of the potential for progressive and devastating outcomes with the failure of treatment. Hence, physicians are largely dependent on anecdotal ex­ perience, animal studies, literature case reports, and un­ controlled clinical series to gain knowledge and treatment guidance for vertebral osteomyelitis and epidural abscess. In this issue of Neurosurgical Focus, articles on the diagnosis, medical management, surgical treatment, and clinical outcomes related to vertebral osteomyelitis and spinal epidural abscess are included. We hope that read­ ers will find pertinent information on the management of vertebral osteomyelitis and spinal epidural abscess from the articles in this issue. (http://thejns.org/doi/abs/10.3171/2014.6.FOCUS14293)

Introduction: Evolving applications of fluorescence technology in neurosurgery

In this issue of Neurosurgical Focus, we will explore the exciting topic of fluorescence-guided surgery (FGS). Neurosurgeons have increasingly relied on FGS for the management of different cerebrovascular and neoplastic lesions. Fluorescence-guided surgery has been established in cerebrovascular neurosurgery with the use of indocyanine green (ICG) angiography. The use of 5–aminolevulinic acid (5-ALA) for fluorescence-guided resection of high-grade gliomas has been widely used around the world for more complete tumor resections. Other tumor types are currently being studied for the use of 5-ALA and FGS. Current regulatory barriers limiting the use of 5-ALA in the US have facilitated the study of other fluorescenceguided technologies for tumor resection. Fluorescein and other fluorophores have demonstrated their own advantages and limitations in the resection of high-grade gliomas. The following collection of papers will provide readers with the most recent information on currently available FGS technologies and the exciting emerging modalities that may advance FGS in neurosurgery. The leading article in this issue by Butte and colleagues reports on a new technology: near-infrared imaging of brain tumors using Tumor Paint BLZ-100. The accompanying editorial by Dr. Roberts further emphasizes the strengths and limitations of this emerging tool. The second article by Coburger and colleagues describes the correlation between 5-ALA intraoperative fluorescence and Gd-diethylenetriaminepentaacetic acid (Gd-DTPA)– enhanced intraoperative MRI findings for tumor detection at the borders of contrast-enhancing lesions. The subsequent article by Acerbi and colleagues reviews their experience with the use of FGS with fluorescein for resection of high-grade gliomas, and the corresponding editorial by Dr. Berger further elucidates the potential of this fluorophore, which does not carry the regulatory limitations imposed on 5-ALA. In a very different application, Roessler and colleagues review important details regarding intraoperative ICG videoangiography assessment for intracranial aneurysm surgery. Januszewski and colleagues describe flow-based evaluation for revascularization, while Marbacher and colleagues review a large series of fluorescence-guided resection of primary brain tumors and brain metastases. Millesi and colleagues discuss their experience with resection of spinal tumors. The other subsequent papers further review emerging applications of fluorescence technologies in neurosurgery. We are very pleased with this issue of Neuro­ surgical Focus and believe the readers will find it very informative. (http://thejns.org/doi/abs/10.3171/2013.12.FOCUS13582)

Introduction: Management of ischemic cerebrovascular disease

The management of ischemic cerebrovascular disease has undergone significant changes in the past 25 years. However, despite enormous advances, there are still many unresolved and controversial issues. This issue of Neurosurgical Focus is dedicated to the current management of ischemic cerebrovascular disease and contains 12 articles evaluating different facets of this disease. Imaging techniques play a major role in allowing better characterization of plaque composition and “instability.” Further refinements will be critical in guiding individualized therapeutic decisions in patients with carotid artery stenosis. In the first article, DeMarco and Huston provide an update on this topic and summarize potential future directions. Despite the landmark trials completed in the past 20 years, the management of asymptomatic carotid artery stenosis continues to be a controversial topic. Progress in medical therapy with the widespread use of lipid-lowering agents and better antihypertensive drugs combined with lifestyle modifications has improved the outlook of patients with asymptomatic carotid artery stenosis. In view of these developments, it may be time to “rethink our therapeutic options” as suggested by the second article in this issue. Current ongoing and planned multicenter studies regarding the optimal management of asymptomatic carotid artery stenosis will not only compare endarterectomy with angioplasty and stenting, but will also include a “best current medical therapy” arm to reflect the ongoing controversy outlined in this article. The management of acute ischemic stroke has undergone dramatic changes. As recently as the early 1990s, a “nihilistic approach” was common among treating physicians faced with a patient with an acute ischemic stroke given the recognition that “little could be done once the stroke has occurred.” Intravenous thrombolysis for patients evaluated within the first few hours after an ischemic stroke has markedly affected this mindset. In patients with large-vessel occlusion who have a contraindication for intravenous thrombolysis or who fail to improve after intravenous thrombolytics, endovascular mechanical clot retrieval has become a rapidly evolving option with high rates of recanalization. The ability to identify “tissue at risk” based on imaging in these patients is very important for proper patient selection. The topic of imaging of acute ischemic stroke is reviewed by Tong and coworkers. Advances in wireless communication and mobile devices continue to dramatically alter the patient-doctor interaction. These recent technological developments have already begun to play a key role in broadening our ability to provide the highest level of expertise to stroke patients who may live some distance from a stroke center, as discussed by Rubin and coworkers in an update on these exciting initiatives. Despite the theoretical appeal of endovascular techniques and the ability to achieve very high rates of recanalization with modern endovascular mechanical devices, the role and efficacy of this therapy has recently been questioned by authors of several multicenter studies. Mokin and coworkers address, in a thoughtful review, the current role of endovascular revascularization for acute ischemic stroke in view of the results of the most recent trials. This article is also featured and discussed in a special podcast accompanying this issue. The 3 subsequent articles are also related to endovascular treatment and include a retrospective analysis of a large cohort of young patients with acute ischemic stroke treated using endovascular recanalization by Chalouhi et al., a review of the current status of endovascular treatment for acute retinal occlusion by Agarwal and coworkers, and a stand-alone editorial by Cloft on issues related to workforce demand in view of recent developments in the treatment of acute ischemic stroke. After the landmark Extracranial-Intracranial (EC-IC) Bypass Study was published in 1985, which showed no Introduction

Introduction: Intractable pain

The problem of surgical pain management remains one of the most daunting in our specialty. Traditionally, we divide the surgical approaches into the more historic destructive procedures (“ablative”) and the more contemporary modulatory ones (stimulation or intrathecal agents). The advent of “evidence-based medicine” has caused us to reanalyze the evidentiary basis of everything we do in neurosurgery, and pain procedures are no exception. What this has taught us is that the evidence to support destructive procedures is almost uniformly absent, although reanalysis using contemporary standards has shown that procedures, such as anterolateral cordotomy, may have a justifiable role in pain control, especially for pain associated with cancer. These same standards of evidence have also revealed weakness in the data supporting neuromodulation, particularly neurostimulation. There is some qualified support for spinal cord stimulation based on reasonably conducted prospective trials, although even these studies are flawed. There is almost no indication that deep brain stimulation was ever effective for pain control, as indicated by a structured review using modern criteria. Peripheral nerve stimulation seems to be flourishing in pain centers worldwide, and yet the data to support this method for a variety of diagnoses are lacking. We are currently in an era in which high-quality evidence to support our surgical endeavors will be increasingly important. With this evidence, it is likely that certain procedures, and perhaps whole fields, will disappear. Our hope is that this issue of Neurosurgical Focus will highlight some of the innovative work that is going on in our field and address some of the challenges of gathering and analyzing the data that will keep the area of pain surgery a vibrant and compelling practice for the future. We are grateful to all of the authors for their contributions to this issue as well as the editors and staff of Neurosurgical Focus for their diligent efforts in support of this cause. (http://thejns.org/doi/abs/10.3171/2013.7.FOCUS13277)

Introduction: Minimally invasive spine surgery: the greatest advance in medicine?

In the past century, significant advances have been made in spine surgery, and in this issue of Neurosurgical Focus, we will review the myriad of treatment options currently available to treat spinal disorders. These minimally disruptive techniques and approaches to the spine have dramatically altered the natural history of previously difficult lesions and spinal conditions. Harvey Cushing would be proud of the work done in the fields of neurosurgery, radiology, engineering, physics, and orthopedics for the advancement of spine surgery. In modern medicine, there are few advances that have had a more meaningful impact on patient outcomes than minimally invasive spine procedures. Patients presenting with painful radiculopathies and neural compression can be treated successfully with minimal access procedures and sent home the same day. Sven Eicker and colleagues discuss their experience with extraforaminal lumbar disc herniations. Their minimal access microsurgical approach with the endoscopic technique seemed to produce less tissue trauma and instability, while providing significant improvement of functional outcomes. Surgical management of tumors, fractures, and spinal deformities has significantly improved with these emerging technologies and techniques. Percutaneous ped icle screw fixation for spine fractures can be done with minimal blood loss, and patients can be mobilized immediately, resulting in a decrease in postsurgical complications. Flexion-distraction spine injuries, which are extremely unstable, classically consisting of a fracture line through all 3 columns, require surgical fixation to avoid neurological deterioration, help stabilize the spine, and restore spinal balance. Historically, these injuries were all treated by means of the standard posterior open approach with instrumented fusion. Percutaneous pedicle screw fixation for these unstable spine injuries has been recently reported in the literature. Andrew Grossbach and colleagues report on their institutional experience of treating these fractures with both surgical techniques and review the current literature. Although it was a small prospective study, there was improvement in kyphotic angulation, and the authors found no significant difference in ASIA scores or the degree of kyphotic angulation between the percutaneous and open surgical groups. Percutaneous pedicle screw fixation appeared to have similar efficacy in the treatment of flexion-distraction injuries, and it allowed for reduced blood loss and tissue damage compared to open surgical techniques. Instrumentation systems have improved significantly in the past 10 years, and today’s hardware allows surgeons to realign the spine and contour the rod to the spine. How about treating spinal stenosis and spondylolisthesis with a minimally invasive interspinous fixation device? Nai-Feng Tian and colleagues found that there was a high incidence of heterotopic ossification after interspinous fixation. Lateral approaches have been applied to treat spinal conditions, such as scoliosis, in recent years. The prior treatment deformity paradigms of shortening the spine by performing osteotomies posteriorly are utilized less. Scoliosis procedures can now be staged with multilevel lateral cages that lengthen the spine, correct the deformity, increase spinal balance, provide a more natural curve, and indirectly decompress neural elements. Armen Deukmedjian and coauthors reviewed their lateral approach for adult degenerative scoliosis. They provided useful data about patient selection for the application of lateral approaches for adult scoliosis surgery. Isolated lateral interbody fusions were deemed suitable for patients with preserved spinal pelvic harmony. Sagittal imbalance may be addressed with advanced lateral approaches, such as releasing the anterior longitudinal ligament. Is there a role for minimally disruptive procedures in the treatment of intradural pathology? The article by Gandhi et al. eloquently describes utilizing a paramedian minimally invasive tubular retractor to access the spine and microscopic instruments to remove intradural pathology. Historically, intradural spinal lesions have been treated from a midline posterior approach using standard microsurgical techniques. The authors retrospectively reviewed their operative blood loss, length of stay, imaging characteristics, and outcomes. Introduction

Introduction: Epilepsy surgery

This issue of Neurosurgical Focus is devoted to epilepsy surgery and includes a variety of topics ranging from technical nuances to edge-of-the-envelope interventions that are just beginning to find their place in surgical management. Eleven papers are included. Some of the new findings and methods that we think will interest readers involve magnetoencephalography (MEG), stereoelectroencephalography (SEEG), and a-methyl-l-tryptophan (AMT)–PET, as well as novel ways of coregistering preand postoperative MR images. We also include a review of optogenetics as it could apply to excitation or inhibition of neural circuits still being studied in animal models. Other reports consider more standard, but no less relevant, issues: complications and specific etiologies such as new-onset refractory status epilepticus and hypothalamic hamartoma. In the report, “Tissue localization during resective epilepsy surgery,” the authors describe methods they use for localization of specific brain regions and implantable electrodes as well as tissue removed by coregistering preand postoperative information from MRI, including functional MRI (fMRI), allowing for the correlation of anatomy, pathology (even at a molecular level), and outcome. Similarly, new methodology for localization is considered in “Correlation between magnetoencephalography-based ‘clusterectomy’ and postoperative seizure freedom,” in which the authors describe using clustering of MEG-derived information from interictal spikes to guide resections, particularly for extratemporal foci. Another report, “Complications after mesial temporal lobe epilepsy surgery via inferior temporal gyrus approach,” considers related complications, which in the authors’ hands showed very acceptable risks. The report, “Seizure control after subtotal lesional resection,” includes the description of a single case as well as a comprehensive literature review of tailored subtotal resection for lesional epilepsy. Also included in this issue is a valuable review of hemispherectomy, “Hemispherectomy: historical review and recent technical advances.” As the title indicates, this paper expands the discussion to more novel imaging and surgical strategies. Another report continues the discussion of hemispherectomy and hemispherotomy—“Disconnective surgery in posterior quadrantic epilepsy: experience in a consecutive series of 10 patients”—but restricts considerations to temporal parietooccipital resections and disconnections accordingly. Stereoelectroencephalography is discussed in the report, “Stereoelectroencephalography for continuous twodimensional cursor control in a brain-machine interface,” in which the methodology of analyzing information from specially designed depth electrodes, each with multiple contacts, is presented. The relevance to localization for epilepsy as well as to brain-machine interfaces is considered. “Optogenetics in epilepsy” presents an overview of futuristic methodology, induction of ion channels using viral vectors, and the use of light to stimulate or inhibit neural circuits. The authors review the work done in animal models and their relevance to human seizures. Several reports consider specific etiologies: inflammation and hypothalamic hamartomas (the latter discussed in 2 parts). “Successful surgical treatment of an inflammatory lesion associated with new-onset refractory status epilepticus” presents a single case and reviews the topic, including a discussion of more standard methods for localization coregistered with molecular information from AMT-PET. The paired reports on hypothalamic hamartomas review this entity in detail as well as management strategies. Epilepsy surgery sits at the juncture of classic anatomical neurosurgery and functional neurosurgery. Surgery to treat epilepsy also provides us with an opportunity to understand neuronal networks. The papers in this issue illustrate some of the issues, challenges, and exciting developments in the field. (http://thejns.org/doi/abs/10.3171/2013.4.FOCUS13138)

Editorial: Magnetic resonance–guided focused ultrasound

In this issue of Neurosurgical Focus, Monteith et al.1 describe an ultrasonic technique for the minimally invasive treatment of spontaneous intracerebral hemorrhage. Historically, this pathological entity has carried a poor prognosis, and its treatment has become the subject of heated debate in the neurosurgical community. In this report, the authors detail an MR-guided technique in which multiple ultrasound beams pass through the calvaria and brain to a deep hemorrhage. Magnetic resonance–guided focused ultrasound (MRgFUS) therapy, through the disruptive forces of multiple ultrasound beams, liquefies the clot and allows it subsequent, minimally invasive aspiration through a bur hole and catheter. Animal and cadaveric studies have delineated no injury to the surrounding brain with the use of this technique. Current drawbacks to this technique include the costs of the MRgFUS system and 3-T MRI, as well as that of the trained, additional staff to operate and troubleshoot the equipment. In addition, current technology allows treatment of lesions only more than 2 cm from the calvarial surface. The potential utility and efficacy of this treatment are promising. Current techniques, including medical management and open cranial decompressive surgeries, are fraught with drawbacks and questionable efficacy. As the authors allude to in their paper, the utility of this ultrasonic technique can only be verified by a pilot clinical trial. Similar techniques have also been applied in a number of other clinical scenarios, including the ultrasonic treatment of metastatic and primary brain tumors as well as functional diseases such as essential tremor and Parkinson disease. The broad applicability of this technology has opened yet another exciting door in the future of neurosurgery.

Introduction: Intracerebral hemorrhage: a changing landscape

This issue of Neurosurgical Focus contains a collection of articles related to changing treatment paradigms for intracerebral hemorrhage. Intracerebral hemorrhage from a variety of causes has been an understudied phenomenon given its prevalence and devastating consequences. New information about natural history, factors influencing outcome, elucidation of additional pathophysiological mechanisms, and neurointensive care management has led to a renewed enthusiasm to improve outcome based on rational treatment paradigms. More recently the introduction of many new anticoagulants and antiplatelet agents has presented new management dilemmas for physicians caring for patients with intracerebral hemorrhage. This collection of interesting papers will hopefully update the reader on current management controversies as well as emerging treatments that may offer promise to improve outcomes in these patients in the future. The first article by Kelly et al. outlines the challenge of surgical decision making when confronted with patients with intracerebral hemorrhage. This timely review summarizes a number of studies regarding the natural history of the condition and factors that influence outcome and are related to the treatment recommendations made to patients and families. The article points out that factors, including geography, treatment biases, patient perceptions, and physician biases, can have a major influence on decision making and selection of different treatments for patients with intracerebral hemorrhages. The next article by Goren and associates focuses on modern intraoperative imaging modalities and how they may be employed in identifying vascular lesions that may be the cause of intracerebral hemorrhage. In the past, the etiology of hemorrhages were often presumed based on characteristic CT appearance, but the important recognition of underlying vascular lesions has been made easier by advances in modern imaging modalities that this article nicely outlines. The next 3 articles deal with the role of decompressive hemicraniectomy in intracerebral hemorrhage patients who are surgically treated and rationales for use of this technique to try to preserve viable brain tissue when treating hemorrhages surgically. The subsequent articles, one by James et al. and the other by Awad et al., detail the use of anticoagulants, antiplatelet agents, and newer agents including Dabigatran and the need for reversal of the effects of these agents in the management of intracerebral hemorrhage. The common use of some of the newer agents for anticoagulation therapy and antiplatelet therapy and their different durations of action, as well as different strategies of reversal of these agents, has required new protocols to be put in place. Close cooperation with blood banks can help effect the reversal of these agents in these patients to limit the expansion of the hemorrhage and can be a prerequisite for surgery, when contemplating surgical treatment. The article by James et al., “The role of anticoagulants, antiplatelet agents, and their reversal strategies in the management of intracerebral hemorrhage,” provides a detailed review of the pathophysiology of these agents and effective treatment strategies. There is a very useful table at the end that will be valuable as a reference guide for clinicians treating these patients. Neugebauer et al. provide a thorough review of the role of managing cerebellar infarction associated with mass effect and various management strategies including ventricular drainage, observation, and surgery. There is a Introduction

Introduction: Cranial nerve surgery

In this issue of Neurosurgical Focus, we have compiled a group of interesting papers related to anatomy, physiology, pathology, and surgery of the cranial nerves. We were very pleased to receive many more submissions of excellent papers on this topic from which we had the difficult task of having to select, because of limitations in space, only 8 papers. Rodgers and colleagues give an excellent review of the syndrome of short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing. In the authors’ case, the syndrome was caused by an epidermoid tumor of the cerebellopontine angle that was clearly compressing the trigeminal nerve. We found this case report interesting because the etiology of this syndrome has not been clear, and this paper suggests that compression of the trigeminal nerve may be one of the causes. We thought that the excellent review of this topic the authors provide to us is important because neurosurgeons are so frequently called upon to treat trigeminal neuralgia, and we must be able to differentiate that condition from this interesting syndrome. Ross and colleagues report on 4 patients with rare facial nerve tumors and use the opportunity to present us with a nice review of the literature on the clinical syndrome, imaging characteristics, and surgical treatment of these tumors. Wang and colleagues from the University of Pittsburgh review their extensive experience with microvascular decompression for hemifacial spasm and conclude that botulinum toxin injections, which many of these patients underwent for treatment of their spasms before microvascular decompression, had no impact on the results of this operation. This finding is important because nowadays most patients have already had this type of palliative treatment before undergoing microvascular decompression. The second paper by this group of authors (Thirumala et al.) is a careful study of neurophysiological monitoring during microvascular decompression for hemifacial spasm; essentially, the authors conclude that changes in interpeak latency of brainstem auditory evoked potentials during surgery do not increase the odds of postoperative hearing loss and should not be used as an “alarm criteria” during microvascular decompression. Kshettry and colleagues present a nice historical review of the early studies of the anatomy of the petroclival region and the contributions of Primo Dorello, an Italian anatomist, after whom the Dorello canal is named. Interestingly, it turns out that the canal now widely known by Dorello’s name had been previously described 50 years earlier by W. Gruber. This paper also contains a nice review of anatomical studies of this region followed by a brief review of clinical implications. Schmidt et al. present a case of a malignant peripheral nerve sheath tumor of the trigeminal nerve, which they used as an opportunity to review the literature and summarize very nicely a total of 36 cases of malignant peripheral nerve sheath tumors of the trigeminal nerve. As expected, these tumors usually present with altered facial sensation and/or facial pain, and it appears that aggressive resection followed by radiation therapy offers the best chance for survival. Sarnthein and colleagues present another interesting paper concerning neurophysiological monitoring of facial nerve function during skull base surgery. In this careful study, the authors find that an intraoperative increase in the threshold for transcranial stimulation necessary to elicit a facial nerve motor evoked response is very specifically correlated with postoperative facial nerve dysfunction, and they suggest that such monitoring should be used in these operations in addition to the widely used direct electrical stimulation of the facial nerve. This issue also contains a very nice review of the neurosurgical options for management of glossopharyngeal neuralgia by Rey-Dios and Cohen-Gadol. The authors conclude that microvascular decompression is an excellent option but that when a convincing neurovascular conflict is not found, section of the glossopharyngeal nerve and the upper rootlets of the vagus nerve is a satisfactory alternative. (http://thejns.org/doi/abs/10.3171/2013.1.FOCUS1322)

The history of skull base surgery

Neurosurgery is of great interest to historians of medicine and technology because it is relatively young, because it developed in an era of journals and publications, because lines and traditions of training and mentorship are relatively clear, and because the technologies that enabled the evolution of the profession and acted as inflection points in the emergence of certain surgical approaches and procedures are at once well documented and remarkably unambiguous. To the extent that is the case for neurosurgery as a whole, it is even more so for surgery of the skull base. To trace the history of skull base surgery along its full expanse is to begin with Horsley and pituitary tumors (unless one wants to start even earlier with the treatment of trigeminal neuralgia); to move to Cushing’s work in the same arena (but also that of many others as well); to emphasize the impact of microsurgical techniques and new imaging modalities; to outline once radically innovative, but now widely practiced anatomical approaches to the skull base; to emphasize the importance of team approaches; to discuss emerging therapeutic strategy as well as instrumentation and techniques; to acknowledge the importance of advances in neuroanesthesia and the medical and perioperative care of the neurosurgical patient; and to recognize the contributions of the many individuals who, over the past 25 years, have added to and furthered the field in these and other ways. It is not hard to point to leading individuals and important techniques. It is perhaps more difficult to frame them in a meaningful historical perspective because the work has occurred relatively recently, in the time frame historians call “near history.” Difficulties arise from both an evaluative and a nosological standpoint. For example, from an evaluative standpoint, how does one stratify the relative importance of corticosteroids, osmotic diuretics, and CSF drainage techniques and technologies in the control of intracranial pressure and the facilitation of exposure for base of skull surgery? How does one think about the idea of hybrid surgery and stereotactic radiation? What will be the long-term view of anatomical approaches to giant basilar aneurysms in the light of endovascular surgery? Have we reached a tipping point in the management of vestibular schwannomas, given the availability of and the outcomes associated with stereotactic radiosurgery? From a nosological standpoint, should we think about base of skull surgery in terms of anatomical approaches? One textbook that does just that starts with subfrontal approaches and then moves around the calvaria and down to the petrous and temporal region in a Cook’s tour of exposure, in the tradition of Henry’s Extensile Exposure and comparable surgical classics.1,6 Other publications have explored a set of technologies.5,7,10 Another focuses on the contribution of great men.9 Many surgeons have written about specific particular pathologies at the skull base.2,8,11 It is likely that the next generation of essays on this subject will reflect the results of molecular diagnostics, genomics, and sophisticate outcome studies as well as currently emerging technologies (such as robotics and heavy particle radiation), and continued innovation in surgical techniques. This issue of Neurosurgical Focus contains a series of essays that discuss various elements of the history of skull base surgery. Lopez-Serna, Elhadi, and Thakur and Introduction

Introduction: Surgery of limbic and paralimbic gliomas

In this issue of Neurosurgical Focus, a challenging neurosurgical entity, gliomas, which grow in the limbic and paralimbic system, is covered from various angles. It is still controversial whether intrinsic tumors in this area should be removed surgically or not. Temporomesial gliomas, and especially those of the insula and cingulate gyrus, are even now widely considered “unresectable.” The aim of this compilation of articles is to provide evidence to the contrary. On the basis of a thorough understanding of functional connectivity and knowledge of the topography, state-of-the-art imaging can be easily interpreted. This will aid in clear preoperative decision making with respect to resectability and imminent risks. It is clear that surgery that is aimed at complete removal has substantial but acceptable morbidity, which is most severe in insular and least severe in temporomesial gliomas. These tumors are closely related to epilepsy or seizures, a fact that is also acknowledged in this issue. Therefore, oncological and seizure aspects of outcome must be considered equally. In both aspects surgery is beneficial. The follow ing articles emphasize also that intraoperative monitoring is of utmost importance during surgery, and that surgery is part of a multimodality treatment concept. Since Yasargil and colleagues 3,4 reported their experience, our group has exhibited particular interest in

Introduction: Vascular Neurosurgery

This issue of Neurosurgical Focus comes at an exciting and perhaps transformational time for those neuroscientists and clinicians involved in the study and treatment of complex cerebrovascular disease. Our diagnostic and therapeutic practices have seen dramatic advances. Imaging capabilities, both anatomical and functional, have improved at a dramatic rate and include neuronavigation modalities for intraoperative guidance, the application of new MR imaging sequences to cerebrovascular disease, and fluorescence angiography to aid in intraoperative decision making.