A novel classification of white fibers of the brain has been proposed based on the direction and depth of the various fiber bundles. The implications of this classification for glioma surgery are presented. Using fiber dissection techniques described by Klingler, the various association, commissural and projection fiber bundles of the brain were studied. The fibers were studied by the naked eye and with the use of magnification. The white fibers of the cerebrum were divided architecturally into five groups- four horizontal groups and one vertical group, based on three dimensional understanding of the white fibers. The four horizontal groups are the superficial, middle, deep and central groups and the vertical group included the projection fibres. The association fibers constitute the superficial, middle and deep groups. The commissural fibers form the central group. In this article, the course of the major fiber bundles of the brain is discussed. The cortical structures and subcortical networks that are involved in major human functions are presented. The implications of the proposed classification of white fibers in the surgical management of gliomas are discussed. Deciphering the cortical and subcortical anatomy of the brain is crucial to avoid neurological morbidity while performing intra-axial brain tumor surgery.

Neuroradiological imaging of gliomas has undergone many advances in the recent years. Visual assessment of structural image datasets is nowadays complemented by quantifiable imaging markers to detect tumor progression and correlations with molecular markers. Detailed information about the tumor-specific pathophysiology, reflected by alterations of hemodynamics and metabolism or about tumor microstructure and infiltration of neighboring structures, is nowadays accessible noninvasively through the magnetic resonance imaging (MRI). Some of these developments have been driven by the updates of the neuropathological classification of gliomas, which now ranks genotypic markers ahead of histomorphological criteria. Neuroimaging constitutes also a key element in the diagnostic support, therapy planning, and monitoring of disease progression under therapy. While computed tomography is still of importance in emergency situations to screen for neoplastic cerebral lesions or acute complications of therapy or tumor progression, as for example, hemorrhage or seizure generation, MRI is the fundamental technology for the differential diagnosis and localization of cerebral gliomas. This review aims at providing an introduction into the most frequent clinically employed advanced magnetic resonance methods for glioma imaging.

Postoperative imaging in primary and secondary brain tumors is becoming challenging due to advancements in molecular genetic classification of brain tumors influencing advancing treatment options. In this review, we summarize the standard-of-care practice, commonly encountered clinical and postoperative imaging issues. The timeline for follow-up imaging in low-grade, high-grade, and secondary tumors is discussed, particularly in reference to tumor and treatment-related effects. Standardized imaging protocols are essential for postoperative evaluation, which should always be read in the context of previous imaging. Where possible, advanced magnetic resonance imaging techniques, including multiparametric diffusion, perfusion, and spectroscopy imaging, should be used to differentiate between recurrent tumor and treatment-related changes. Surgical complications are often seen in the immediate and acute postoperative period and chemoradiotherapy-related complications following several weeks to months. The main aim of postoperative imaging is to evaluate expected and unexpected findings for appropriate management. Background information of tumor molecular genetics, histological grade, patient clinical status, and treatment given is essential for interpreting postoperative imaging.

Meningiomas are the most common tumors of the cavernous sinus (CS) and are one of the most challenging/formidable tumors to operate on due to the complex anatomy and rich neurovascular contents of the space. Parkinson's initial approach to this surgical “no man's land” triggered the interest in the microsurgical removal of tumors within this region over the next three decades. However, this initial enthusiasm to attempt complete removal of meningiomas has been met with exceedingly high surgical morbidity, especially cranial nerve palsies, and considerable mortality, predominantly due to vascular complications. The later introduction of radiosurgery and its excellent tumor control rate and minimal complications has allowed surgeons to select less invasive approaches such as primary radiosurgery or partial resection followed by radiosurgery. The authors aim through this work to discuss the relevant microsurgical anatomy, evolution of approaches, and techniques of CS meningioma excision including the endoscopic endonasal approach. We discuss the available alternatives and adjuvant management options, proposing an up-to-date multimodality treatment algorithm to optimize outcomes.

Introduction: Pineal cysts have proven to be a challenging pathology for neurosurgeons. Due to occasional nonspecific symptoms, as well as a wide range of possible morphology and diagnoses, literature is scarce, and little evidence-based management guidelines exist. Methods: We present a retrospective review of 38 patients who underwent a surgical resection of a pineal lesion in a single center by a single surgeon between 2012 and 2018. Symptoms, imaging characteristics of the lesion, pathology report, and postoperative radiographic and clinical outcomes were collected. Results: Thirty-eight patients were selected. The most common preoperative symptoms included headaches (97%), visual disturbances (89%), cognitive disturbances (58%), and nausea/vomiting (53%). Preoperative radiographic measures showed no relationship to the pathological diagnosis of pineal cyst or pineocytoma (P > 0.05) except for mass effect on the tectal plate that was associated with pineocytoma (P < 0.05). Lesion pathology breakdown: 23 (60%) – World Health Organization Grade I pineocytoma, 14 (37%) – simple pineal cysts, and 1 (3%) – pineal parenchymal tumor of intermediate differentiation. The mean follow-up was 24 months. Headaches and visual disturbances were relieved in 78% and 58% of patients, respectively. Cognitive disturbances were found to be correlated with pineal cyst (P < 0.01). Patients with hyperintense fluid-attenuated inversion recovery signal and enhancement on preoperative magnetic resonance imaging were found to be at higher risk of not experiencing full symptom resolution (P < 0.05). Finally, if no symptom resolution occurred, then higher chance of patients not returning to work was seen (P < 0.05). Conclusion: Albeit challenging to treat, careful examination of presurgical imaging findings and surgical resection of appropriately selected pineal lesions can lead to significant relief of preoperative symptoms and overall meaningful improvement.

Tumors in the foramen magnum region are among the most challenging neurosurgical lesions to operate. They may be divided into intradural and extradural tumors, which have differing pathologies. Meningiomas represent the most common intradural tumor in this region. Anatomical constraints caused by adjacent critical areas of the brainstem, proximity to the lower cranial nerves (CNs), and vertebral arteries add to the complexity and make total tumor resection difficult without damaging the brain stem, CNs, or the vertebral artery and branches. This review article summarizes the surgical approaches and relevant anatomical landmarks with illustrations at each step. We also illustrate with example cases, the decision-making process and highlight key strategies for the safe resection of these tumors.

Orbit can be home for a spectrum of tumors with almost every orbital structure having the potential to harbor a neoplastic process. Surgical exposure and resection of orbital tumors can often be tricky due to the intricate anatomy of the region, with an additional complexity caused by a tumor related distortion. The clinical presentation depends on the primary structure involved and the location of the tumor within the orbit, and so does the scheme of management. Modern diagnostic imaging modalities offer a crucial pre-operative understanding of the precise location of the tumor within the orbit; it also helps in defining the nature of the tumor. Both these aspects are required for planning the appropriate surgical approach. Often, orbital tumors extend beyond the confines of the orbit requiring the tailoring of the surgical procedure, which may necessitate the involvement of a multidisciplinary team. The contemporary neurosurgical practice is also witnessing a progressive inclination towards minimally invasive endoscopic approaches, which have shown equally good if not better results in properly selected cases. Furthermore, early promising results with attempts at performing multisession stereotactic radiosurgery on orbital tumors has rekindled interest in this modality, in line with the management of intra-cranial tumors having a similar pathology. This article aims to recapitulate relevant surgical anatomy and to elucidate the current practice in the management of common orbital tumors encountered by neurosurgeons.

Giant pituitary adenomas (GPAs) are a subset of pituitary tumors characterized by their large size and invasive nature. Diverse surgical techniques including microscopic transsphenoidal, endoscopic transsphenoidal, transcranial transcavernous, and a combination of both suprasellar and infrasellar techniques have been developed to treat such giant tumors with extension into surrounding structures. In this review, we attempt to summarize the different operative strategies, nuances, the pearls and pitfalls of different techniques, and the outcome following surgery for GPAs..

The calvaria or skull vault, in general, has a limited spectrum of oncological disorders which are both unique to it and ubiquitous throughout the body. Lesions of the calvarium may originate from the bony structures or may be secondary to an invasion of scalp-based lesions or brain-based lesions into the skull vault.A PubMed/Medline search was conducted using the MESH keywords “Calvarial tumors”, “Bony tumors”, “Skull base bony lesions” and all reported cases and series were collected, and relevant details extracted from the same. Data were extracted concerning the type of study, the number of cases, follow-up duration, the primary treatment offered, details of adjuvant therapy, overall survival, and recurrence rates where relevant. All data were then tabulated and reviewed. Cases showing relevant information on treatment modalities and their effect on outcomes and survival were only included. A total of 1020 results were found on the PubMed database (until March 2021) and after duplicates removal, a total of 9 studies were found to be relevant for calvarial tumors with 1 case series and 4 retrospective reviews of intraosseous meningiomas which included 2 review papers as well. Most of these results were either retrospective case series or case reports along with a single systematic review of intraosseous meningioma. The primary treatment modality in almost all cases was either surgery or biopsy followed by adjuvant radiotherapy. The skull base and cranial vault is a Pandora's box of malignancies with varied shapes and appearances. Presentation is either due to pressure symptoms or swellings, and whenever accessible, complete excision offers the best management. Imaging findings are of germinal importance and help differentiate lesions, which often decides management. When in doubt, a biopsy may offer the best solution. Bony reconstruction and adjuvant therapy with close follow-up often decide prognosis.

Optimizing the extent of resection remains a primary goal of surgery for diffuse gliomas and most brain tumors. Limitations of capabilities of human visualization necessitate the use of adjuncts to augment and improve outcomes. This review serves to encapsulate the commonly used adjuncts in neurosurgical oncology. There exists a plethora of such techniques which can broadly be divided into image-guided techniques (including navigation and real-time intraoperative imaging modalities such as ultrasound, computed tomography, and magnetic resonance imaging) as well as optical imaging techniques (of which fluorescence is the most widely used one). This review describes these techniques briefly and reviews pertinent literature focusing on the utility and benefits of these modalities. Both diagnostic accuracy and the therapeutic outcomes are discussed. Although each modality is supported by published literature, the quality of the evidence is variable. It is difficult to make comparisons across studies due to variability in study design, populations included, and the techniques used for the assessment of outcomes. It is likely that a combination of modalities will be synergistic and judicious use of the range of adjuncts is advisable.

Intraoperative neurophysiological monitoring (IOMN) is an important adjunct in modern day neurosurgical practice. There has been a paradigm shift from functional preservation to maximal safe or total excision of a tumor along with functional preservation, aiming for a better quality of life to the patients. In neurosurgery, like in any other specialty, we have two extremes of tumors, benign and malignant. In malignant tumors, the extent of resection, along with molecular genetics of the tumor, play an important role in the survival of patients. Thus, one should target for complete resection, whenever feasible, in these types of tumors. In benign tumors, such as World Health Organisation (WHO) grade 2 gliomas, a good chance of long-term survival exists. IOMN is a valuable adjunct in neurosurgical practice that guides the surgeon and warns him/her of the important neurological structures in the vicinity, during surgery. The IOMN procedures, however, have their own limitations that everyone should be aware of. The technique has been used along with other adjuncts like a preoperative MRI (including the functional magnetic resonance imaging [MRI], diffusion tensor imaging of long tracts and perfusion studies), neuronavigation and intraoperative imaging to maximize the chances of a better outcome in the form of onco-functional balance. In this review, an overview of IONM has been discussed.

Recent research has promoted elucidation of the diverse biological processes that occur in pediatric central nervous system (CNS) tumors. These molecular data are leading to new guidelines for the diagnosis, offering prognostic implications and novel molecular targeted therapies. The consortium to inform molecular and practical approaches to CNS tumor taxonomy-NOW have made practical recommendations using recent advances in CNS tumor classification, particularly in molecular discernment of these neoplasms as morphology-based classification of tumors is being replaced by molecular-based classification. Here, we review the specific molecular drivers that help to define the entities that fall under the umbrella of pediatric gliomas and how to effectively test them in cost-effective manner. We discuss briefly the proposed risk-based stratification system that considers both clinical and molecular parameters to aid clinicians in making treatment decisions and the availability of an increasing array of molecular-directed therapies.

Challenges in obtaining tissue specimens and tumor heterogeneity are major limitations for accurate diagnosis, molecular characterization, risk stratification, and development of biomarker-driven therapies in central nervous system (CNS) tumors. The potential of assessment of CNS tumors through analysis of corporeal fluids (liquid biopsy) is being explored to document tumor-related genetic/epigenetic alterations and protein expression to identify prognostic and therapeutic biomarkers. The quantity of circulating tumor DNA isolated also appears to be directly associated with tumor progression and response to treatment. In this review, we provide synopsis of the recent studies which have provided crucial insights into analyzing circulating tumor cells, cell-free nucleic acids, and extracellular vesicles for directing long-term disease control. We have also highlighted the stumbling blocks and gaps in technology that need to be overcome to translate research findings into a tool in the clinical setting.

Central nervous system (CNS) embryonal tumors exhibit significant biological heterogeneity and pose challenges in diagnosis and clinical management. Among these, medulloblastoma is the most common and extensively studied tumor. Advances in understanding the molecular alterations of these tumors, using genomic and epigenomic platforms, have led to refinement in their diagnosis, classification, and guiding clinical management. This review discusses the current understanding of the molecular underpinnings of CNS embryonal tumors and details their clinical presentation, histopathological, and molecular features. Based on the recent discoveries, the current state of management of medulloblastoma and other embryonal tumors, including the recent biomarker-based clinical trials, is reviewed.

Radiation therapy (RT) plays a key role in the optimal management of a range of primary and secondary brain tumors. RT has evolved from conventional radiotherapy to three-dimensional (3D) conformal, intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), stereotactic techniques such as stereotactic radiosurgery or fractionated stereotactic radiotherapy to particle beam therapies such as the proton beam therapy (PBT) and carbon ion therapy. Further, there is increased evidence of molecular-based approach in the treatment of malignant brain tumors. Tumors such as the high-grade gliomas tend to have inferior outcomes as compared to the low-grade gliomas. Pediatric brain tumors tend to do better, in terms of local control, progression-free survival, and overall survival. In such scenarios, sparing of critical structures is essential as it tends to reduce the dose to the normal brain tissue, thereby improving neurocognitive outcomes, reduces hormonal impairment and risk of secondary malignant neoplasms. Modern techniques such as the IMRT, VMAT, and PBT, especially image-guided intensity-modulated proton therapy, spare the critical structures to bare minimum, which in turn leads to superior dose distribution without any low dose spillage to the nearby areas. These advanced techniques not only behave therapeutically but are also cost-effective, resulting in improved quality of life.

Gamma knife radiosurgery (GKRS) is a popular radiosurgical tool for various benign and malignant intracranial pathologies. Our objective was to evaluate the spectrum of complications of GKRS, the timeline of adverse events, and the outcome following the radiosurgical intervention. We systematically searched for articles related to various complications using the following keywords: “Vascular complications”, “Gamma-knife”, “stereotactic”, “radiosurgery”, “complications”, “edema”, “vascular changes”, “malignancy”, and “alopecia”. The literature was separately evaluated for 'early ' (within 12 weeks of GKRS)' or 'delayed' (after 12 weeks of GKRS) sequalae. We separately evaluated the relevant animal studies for literature analysis, and for the histopathological changes that take place after radiosurgery. Following the systematic analysis, 543 articles were evaluated. With the predetermined criteria, we identified 36 studies detailing 72 cases. Vascular complications, radiosurgery induced malignancy, radiation necrosis and radiation induced edema were the major reported complications. A delayed hemorrhage after a latency period was the most common complication while administering GKRS for arteriovenous malformations. A repeat radiosurgical intervention was identified as the significant factor responsible for delayed hemorrhage. Post-radiosurgery intratumoral hemorrhage was observed in meningiomas, vestibular schwannomas, pituitary adenomas, pineocytomas and cerebellar astrocytomas. Following the administration of single fraction stereotactic radiosurgery (SRS) for brain metastases, necrosis was observed in 5.2% patients at 6 months, in 17.2% at 12 months, and in 34% patient population at 24 months. Delayed occlusive or proliferative vasculopathy, malignancy, necrosis and edema are rare, albeit probable, complications that occur after GKRS. There are no definite identifiable markers for determining the probability of developing these complications. The risks of radiosurgery-induced complications are more in patients with a history of prior radiation therapy, a large tumor volume, and the usage of non-conformal dose plans. The risk of radiation-induced tumour formation after a single-function radiosurgery is very low and should not be used as a reason to choose alternative treatment strategies for appropriate patients. The clinician should explain these probable risks to the patient before considering GKRS as a treatment option.