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BACKGROUND: Posterior fossa irradiation with or without whole brain irradiation results in high doses of radiation to the thalamus, hippocampus, and putamen, structures critical to cognitive functioning. As a result, children with brain tumors treated with cranial irradiation (CRT) may experience significant cognitive late effects. We sought to determine the effect of radiation to those structures on neuropsychological outcome. METHODS: Forty-seven children with a history of posterior fossa tumor (17 treated with surgery; 11 with surgery and chemotherapy; and 19 with surgery, chemotherapy, and CRT) underwent neuroimaging and neuropsychological assessment at a mean of 4.8 years after treatment, along with 17 healthy sibling controls. The putamen, thalamus, and hippocampus were segmented on each participant's magnetic resonance imaging for diffusion indices and volumes, and in the radiation treatment group, radiation dose to each structure was calculated. RESULTS: Performance on visuoconstruction and spatial learning and memory was lower in patient groups than controls. Volume of the thalamus, when controlling for age, was smaller in the patient group treated with CRT than other groups. Higher radiation doses to the putamen correlated with higher fractional anisotropy in that structure. Higher radiation dose to the hippocampus correlated with lower spatial learning, and higher dose to thalami and putamina to lower verbal and nonverbal reasoning. CONCLUSIONS: All children with posterior fossa tumors, regardless of treatment modality, had cognitive deficits compared to their sibling controls. Posterior fossa irradiation may affect thalamic volume and aspects of verbal and nonverbal cognitive functioning.

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Posterior fossa decompression for symptomatic Chiari malformation is an effective and frequently performed procedure, but it does carry risks of significant complications including cerebrospinal fluid leak and craniocervical instability. Patients sometimes do not improve or worsen after decompression, which may discourage neurosurgeons from performing Chiari decompression surgery. In this chapter, management strategies and surgical approaches are discussed that minimize the risks of complications and maximize favorable outcomes in Chiari malformation surgery.

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OBJECTIVE: Arachnoid cysts are benign, intradural collections of cerebrospinal fluid that are often asymptomatic but, in rare instances, will grow and may cause symptoms. When these are in the posterior fossa, the symptomatology greatly ranges, and the indications for surgery are not well defined. The objective of this study is to examine radiographic and symptomatic outcomes following surgery for posterior fossa arachnoid cysts (PFAC). METHODS: A literature review was performed utilizing PubMed for all studies involving ≥ 5 patients with PFACs who underwent surgery. A single-arm meta-analysis was performed to assess the postoperative radiographic improvement. Given the heterogeneous variety of presenting symptoms, these were not conducive to meta-analyses but the outcomes are reported in detail. RESULTS: Nine publications with 67 patients met inclusion criteria. Excision/fenestration was the most common operation (n=60). Less common included CP shunts (n=2), concurrent excision/fenestration and ETV (n=4), and one patient who underwent concurrent VP/CP shunts. This literature review revealed improvement of headache in 90% of patients; 88% with cerebellar symptoms; 92% with nausea/emesis; 78% with hearing loss; 60% with tinnitus; and 91% with vision deficits. Meta-analysis of seven studies reporting postoperative radiographic size demonstrated that 75% of people experienced decreased PFAC size (Effect Size: 0.75, 95% CI: 0.50-0.94). CONCLUSIONS: Although there is a high rate of radiographic improvement for PFAC surgery, there is a wide variety of presenting symptoms with differing postoperative improvement rates. This study reinforces the importance of preoperative counseling regarding symptomatic outcomes for PFAC surgery, with supporting statistical analysis but limited by the sample sizes available.

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(1) Background: Intensive interdisciplinary rehabilitation services more effectively promote recovery from acquired brain injury than a single discipline approach. However, research literature is lacking regarding the perceived feasibility and utility of an interdisciplinary approach across disciplines for patients within a tertiary care pediatric hematology/oncology setting. (2) Methods: The Acute Neurological Injury (ANI) service applied an acquired brain injury/inpatient rehabilitation interdisciplinary approach to a pediatric hematology/oncology population, with a focus on interdisciplinary communication, shared goal setting, and coordinated transition planning. Caregivers whose children received coordinated ANI program care were interviewed regarding the perceived feasibility and utility of ANI program components. (3) Results: An interdisciplinary approach to a pediatric hematology/oncology population is feasible for caregivers and for providers of rehabilitation and psychosocial services within a tertiary care cancer hospital setting. Parents perceived benefits from aspects of this approach including coordinated interdisciplinary care planning, the implementation of an interdisciplinary goal, parent brain injury education, neuropsychological assessment reports, and weekly cognitive intervention sessions. Parents were interested in both having a peer mentor while managing new cancer diagnoses and later serving in a mentor role for a newly diagnosed family. (4) Conclusions: An interdisciplinary acquired brain injury approach to a pediatric hematology/oncology population is feasible with perceived benefits to families managing new cancer diagnoses.

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The majority of children's brain cancers are posterior fossa tumours, which include brainstem gliomas, medulloblastomas (MBs), juvenile pilocytic astrocytomas, and ependymomas. This report details a 13-year-old female presenting with headache, nausea, and ataxia. With typical magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) results, the MRI indicated a solid lesion in the fourth ventricle, producing obstructive hydrocephalus. Pilocytic astrocytoma, ependymoma, MB, and other conditions are examples of differential diagnoses. In addition to underscoring the need for early intervention to enhance prognosis and outcomes for paediatric patients with posterior fossa tumours, the case highlights the vital role that sophisticated imaging plays in early detection and therapy.

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BACKGROUND: Hemorrhage management is crucial for surgical resection of pediatric posterior-fossa tumors (PPFTs). Tumor volume and vascularity on preoperative magnetic resonance imaging (MRI) can help predict and control intraoperative blood loss (IBL). The present study aimed to assess the correlation between MRI features and IBL in PPFTs. METHODS: Eleven patients treated for PPFTs at our hospital using the transcerebellomedullary fissure approach were enrolled, including five (45.5%) males and six (54.5%) females, with a median age of 10 (range, 4-16) years. Nine patients with medulloblastoma, one with ependymoma, and one with atypical teratoid/rhabdoid tumor were included. Using susceptibility-weighted imaging-based intratumoral susceptibility signal (ITSS) grade as an index of tumor vascularity, we performed univariate analysis of the association of degree of vascularity (ITSS grade 0-2 vs. 3) and multivariate analysis of IBL. RESULTS: Univariate analysis showed that the high vascularity group (ITSS grade 3) had significantly larger tumor volume (p = 0.009) and higher IBL (p = 0.004). In multivariate analysis of age, tumor volume, ITSS grade, cerebral blood volume, and extent of resection, tumor volume was the only significant factor (p = 0.001); however, ITSS grade was also positively associated with IBL (p = 0.074). CONCLUSION: In this study, tumor volume and vascularity of PPFTs were strongly correlated, and tumor volume was the sole factor significantly associated with IBL. This study suggests that ITSS grade and tumor volume collaboratively influence IBL in surgical resection of PPFTs. IBL should be assessed based on MRI features, and suitable treatment strategies should be established.

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The posterior fossa is a limited compartment therefore lesions compressing its structures can result in devastating outcomes. It can cause significant neurological deficit due to mass effect on critical structures and hydrocephalus. Due to the nature of the infratentorial region, urgent surgical intervention is often the first-line option. Surgical neuro-oncologists guide patients and caregivers through the course of this disease and to inform them about the various options for management and long-term outcome optimisation. There is currently conflicting data; however, institutional experiences can guide us towards achieving improvements in surgical outcomes and quality of life. Advances in molecular classifications coupled with highdose radiation treatment improve our capacity for improving overall survival in these patients. Common childhood tumours are ependymomas, medulloblastomas, and juvenile pilocytic astrocytomas, while adults often present with metastases, and less commonly, cerebellar haemangioblastomas and gliomas. This paper outlines management strategies with consideration for multidisciplinary care and resourcelimited settings.

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Progressive Multifocal Leukoencephalopathy (PML), primarily affecting immunocompromised individuals due to the John Cunningham virus (JC), is common in HIV-positive adults but rare in paediatrics. We present a unique case of a 14-year-old female with PML as the initial manifestation of HIV, with MRI lesions isolated to the posterior fossa. Initial symptoms included fever and rash, progressing to neurological deficits and ataxia. Severe immune suppression due to HIV and JC virus in the cerebrospinal fluid were confirmed. Management included immune reconstitution therapy (antiretroviral treatment) and supportive care. Despite interventions, the patient had a slow recovery with significant residual neurological sequelae. Timely recognition of Immune Reconstitution Inflammatory Syndrome (IRIS) and steroid initiation proved helpful. Antiretroviral therapy improved the survival rate of HIV-related PML, but long-term neurological sequelae, especially in posterior fossa cases, significantly impact the patient's quality of life. This case highlights diagnostic and treatment challenges in paediatric PML, particularly with atypical lesions location.

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INTRODUCTION: The threat posed by tuberculosis persists in developing countries. Individuals under the age of five were more likely to develop central nervous system (CNS) tuberculosis. CNS Tuberculoma of the posterior fossa has rarely been reported, and its consequences are more devastating due to the limited space of the posterior fossa. CASE PRESENTATION: A 4-year old male was referred to our academic general hospital with main complaint of decreased consciousness for the last 3 days. The patient has experienced a low-grade fever, cough, and an enlarging neck tumor for two months. Any contact with confirmed tuberculosis patients was denied by the family. A suspected cerebellar abscess and obstructive hydrocephalus led to the patient's referral. Urgent evacuation of the posterior fossa mass was conducted, revealing a histopathological diagnosis of tuberculoma. After the procedure, the patient experienced seizures and no improvement of GCS. A head CT scan evaluation revealed a communicating hydrocephalus. A ventriculoperitoneal shunt is done, resulting in improvement of the patient's consciousness after CSF diversion. DISCUSSION: The haematogenous spread of Mycobacterium, which causes granulomatous foci in the brain, is the cause of CNS tuberculoma. The neuroradiological characteristic of tuberculomas may mimic several conditions. Thorough history-taking and physical examination may lead to a focused differential diagnosis of the patient. Evacuated posterior fossa tuberculoma usually leads to resolved obstructing hydrocephalus. A persistent hydrocephalus leads to the possibility of communicating hydrocephalus due to tuberculous meningoencephalitis. Close monitoring following excision of posterior fossa tuberculoma may help identify persistent hydrocephalus early on. CONCLUSION: CNS tuberculoma should remain a differential diagnosis of ring-enhancing posterior fossa mass, especially in pediatrics. This condition may present concomitantly with tuberculous meningoencephalitis, and it may be presented as a persistent hydrocephalus following the surgical removal of the lesion.

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Cerebrospinal fluid drainage is a common practice to provide brain relaxation during intradural surgery. In retrosigmoid approaches, cerebrospinal fluid can be drained from the cisterna magna to provide brain relaxation in the posterior fossa. To our knowledge, most techniques to achieve cerebrospinal fluid release concern intradural opening of the cisterns. We describe a novel way for the extradural opening of the cisterna magna in retrosigmoid surgery that avoids direct cerebellar contact. Patients elected for surgical treatment of cerebellopontine angle tumors are positioned supine with a roll under the ipsilateral shoulder and the head turned to the contralateral side. After performing a retrosigmoid craniotomy, the surgical microscope is tilted, and the foramen magnum is approached extradurally. A horizontal dural slit is made at the level of the cisterna magna, and cerebrospinal fluid is drained without having direct cerebellar contact. After brain relaxation, the intradural surgery can proceed as usual. This slight adaptation for a very common practice avoids the need for direct cerebellar retraction when approaching the cisterna magna to drain cerebrospinal fluid. It is a clean and easy step to perform, that we believe improves surgical efficacy and could potentially diminish cerebellar harm because it obviates the need for intradural opening of the cisterna magna.

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BACKGROUND: Chiari malformation type I (CM-1) is a complex disorder in which tonsillar herniation through the foramen magnum manifests with a spectrum of clinical symptoms. This work analyzes morphometric and volumetric characteristics of CM-1 patients. METHODS: With Institutional Review Board (IRB) approval, we retrospectively reviewed a total of 72 adult CM-1 patients and 26 healthy adult volunteers who underwent volumetric magnetic resonance brain imaging. Clinical data was retrospectively extracted from the electronic medical record. We analyzed multi-dimensional morphometric and volumetric features within the posterior cranial fossa and correlated these features with syrinx formation and the decision to undergo surgical decompression. RESULTS: In our study, CM-1 patients had decreased cerebellar, brainstem and 4th ventricular volumes but larger tonsillar volume with increased total tonsillar length. CM-1 patients who underwent surgery had significantly more neural tissue within the cross-sectional area of cisterna magna. Logistic regression demonstrated that combining neural tissue at foramen magnum with cerebellar & 4th ventricular volumes led to great degree of correlation with syrinx formation (AUC 0.911). CONCLUSIONS: Our findings suggest that the amount of tissue at the foramen magnum correlates with CM-1 patients who underwent decompressive surgery, more so than tonsillar length. Additionally, the combination of neural tissue at foramen magnum, cerebellar & 4th ventricular volumes led to great degree of correlation with syrinx formation. Together, these findings suggest that a global compressive phenomenon within the posterior fossa leads to CM-1 symptomatology and syrinx formation.

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Dural arteriovenous fistulas (dAVFs) are anomalous connections between arteries and veins within the dura mater, involving dural sinuses, bridging veins, or emissary veins. If untreated, these lesions can result in intracranial hemorrhage. The management of posterior fossa dAVFs is challenging due to the intricate venous anatomy near the brainstem and cranial nerves. This study leverages three-dimensional (3D) technology combined with dissections to understand the anatomy and microsurgical techniques for treating infratentorial dAVFs. Five embalmed heads and one dry skull were used to meticulously document the pertinent anatomy of the infratentorial compartment. Advanced 3D technology, including 3D sculpting and structured light scanning, was employed to construct high-resolution volumetric models (VMs). Two-dimensional (2D) images of dissections and VMs illustrate key anatomical landmarks of the posterior fossa. Infratentorial dAVFs primarily involve sinuses, which are divided into groups based on their location: basal, medullary, and petrosal. Most of the arterial supply originates from the external carotid artery, especially the ascending pharyngeal artery. This is followed by meningeal branches from the internal carotid artery (ICA) and vertebrobasilar system. The surgical approaches to treat infratentorial dAVFs include the retrosigmoid and far lateral approaches and their modifications. Our study describes the relevant vascular anatomy of the infratentorial compartment, focusing on the surgical treatment of infratentorial dAVFs. In conjunction with the included interactive models, this study improves our educational capabilities regarding the intricate vascular neuroanatomical features of this region. When applied to a clinical setting, precise anatomical knowledge and VMs tools enhance surgical outcomes, reduce complications, and ultimately improve patient care.

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The central nervous system (CNS) is less prone to infection owing to protection from the brain-blood barrier. However, craniotomy destroys this protection and increases the risk of infection in the brain of patients who have undergone craniotomy. CNS infection after craniotomy significantly increases the patient's mortality rate and disability. Controlling the occurrence of intracranial infection is very important for post-craniotomy patients. CNS infection after craniotomy is caused by several factors such as preoperative, intraoperative, and post-operative factors. Craniotomy may lead to postsurgical intracranial infection, which is mainly associated with surgery duration, infratentorial (posterior fossa) surgery, cerebrospinal fluid leakage, drainage tube placement, unregulated use of antibiotics, glucocorticoid use, age, diabetes, and other systemic infections. Understanding the risk factors of CNS infection after craniotomy can benefit reducing the incidence of intracranial infectious diseases. This will also provide the necessary guidance and evidence in clinical practice for planning to control intracranial infection in patients with craniotomy.

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Background: The Precentral Cerebellar Vein (PCV) plays a crucial role as an anatomical landmark in neurosurgery, and the possibility of its safe sacrifice is controversial. Understanding its anatomical nuances and clinical implications is fundamental in enhancing neurosurgical practice. Methods: A systematic review following PRISMA guidelines was conducted to consolidate literature on the PCV. PubMed, Scopus, and Web of Science were systematically searched using predefined criteria. Studies providing complete research texts in English, focusing on the PCV's surgical anatomy and neurosurgical implications were included. Results: Fourteen articles met inclusion criteria, exploring the PCV's anatomical variations, trajectory, dimensions, and connections. The PCV's utility in localizing posterior fossa tumors was underscored, aiding in surgical precision. However, sacrifices of the PCV or minor veins for access to quadrigeminal areas posed postoperative risks, emphasizing the need for careful preoperative planning. Additionally, the PCV's diagnostic value in venous malformations and developmental anomalies was highlighted. Conclusions: This comprehensive review accentuates the pivotal role of the PCV in neurosurgery. While serving as a vital guide in procedures, it poses potential risks when manipulated. Understanding its multifaceted significance, from anatomy to clinical implications, is paramount for informed decision-making and minimizing complications in neurosurgical interventions.

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AIMS: The cerebellum is a key structure in working and procedural memory. The aim of the present prospective exploratory study was to investigate, the metabolic characteristics of the cerebellum in posterior fossa tumor (PFT) survivors using 3D proton magnetic resonance spectroscopy imaging (3D MRSI), to determine whether metabolites could be useful biomarkers of memory impairment. MATERIALS AND METHODS: Sixty participants were included in the IMPALA study, divided into three groups: 22 irradiated PFT, 17 nonirradiated PFT, and 21 healthy controls matched with irradiated PFT for age, sex, and handedness. PFT survivors were treated at least 5 years ago, either by surgery or a combination of surgery, chemotherapy, and radiotherapy. All participants underwent working and procedural memory tests and multimodal MRI including a 3D MRSI sequence. N-acetylaspartate (NAA), choline (Cho), creatine (Cr), and lactate (Lac) metabolite values were extracted from the cerebellum for comparisons between groups, correlations with neurocognitive test scores, and radiotherapy doses. RESULTS: Median (range) age at neurocognitive tests was 18 (7-26) years. Median Cho, Cr, NAA, and Lac values, and the ratio of NAA to the sum of metabolites were significantly lower for PFT survivors than for healthy controls (p < 0.05). Scores on working and procedural memory tests were significantly lower for PFT survivors (p < 0.004) and correlated with median and maximum Cho and NAA values (0.28

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Ependymoma occurring at the cerebellopontine (CP) angle is an extremely uncommon sight and poses diagnostic and management dilemmas to neurosurgeons, radiologists, and neuropathologists alike. Moreover, the presence of extensive chondro-osseous metaplastic elements in ependymomas is an exceptionally infrequent histopathological manifestation. However, due to the seldom-seen nature of this histomorphological feature, there is no definite consensus regarding its etiopathogenesis and clinical consequences, and there is an extreme scarcity of literature elucidating its clinicopathological spectrum and prognostic significance. Herein, we illustrate an intriguing clinical tale of a 7-year-old male child with posterior fossa ependymoma, central nervous system (CNS) World Health Organization (WHO) grade 3, arising at the right CP angle and masquerading as a vestibular schwannoma, which in itself is a rare presentation, and additionally, exhibiting extensive chondro-osseous metaplasia, which is a very uncommon histomorphological observation. To the best of the authors' knowledge and after a comprehensive literature search, the coexistence of these two rare observations has merely been described once in international literature. This case sheds light on and highlights the importance of keeping ependymoma as a possible differential while coming across CP angle space-occupying lesions. They should be diligently distinguished from schwannomas and other masqueraders that typically occur at this site, as they have diverse management and follow-up protocols, with varying prognostic outcomes for the patients. Moreover, this case also unravels and details the clinicopathological characteristics of a scarcely described feature of chondro-osseous metaplasia in ependymomas.

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OBJECTIVE: We designed this study to introduce the surgical strategy cerebrospinal fluid (CSF) decompression in treatment of Chiari malformation type I and compared CSF decompression with other surgical strategies to provide a solid basis for patient counseling. METHODS: The study enrolled 528 consecutive patients with CMI who underwent surgical interventions from 2012 to 2022. The surgical strategy for these patients was bony and dural decompression, anatomical reduction of herniated tonsils, or CSF decompression. Short-term results were determined after 3 months; long-term outcomes were evaluated at last follow-up (at least 18 months). RESULTS: CSF decompression was independently associated with better long- or short-term primary outcomes than anatomical reduction of herniated tonsils or bony and dural decompression (P < 0.001). Compared with short-term, the long-term outcomes were better in patients who underwent CSF decompression (P = 0.035), but were worse in patients with bony and dural decompression (P = 0.03). Specific surgical techniques cannot affect the long- and short-term outcomes of patients with Chiari malformation type I. CSF decompression provided better long-term syringomyelia improvement than short-term (181/218, 83% vs. 169/218, 77.5%; P < 0.001). CONCLUSIONS: CSF decompression, but not a specific surgical technique or operative method, was associated with favorable neurological outcomes in ADULT patients with Chiari malformation type I. The surgical technique and operative method should be selected according to the characteristics of each patient and the intraoperative condition to normalize CSF circulation at the craniovertebral junction area. The intraoperative target, smooth CSF flow out from the fourth ventricle and in to the bilateral Luschka foramina, could be observed.

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OBJECTIVE: The rhomboid lip is a neural tissue encountered during cerebellopontine angle surgery, with differing shape and extent among individuals. This study aimed to investigate the variation of rhomboid lips during posterior fossa surgery. METHODS: In this retrospective study, we examined posterior cranial fossa surgeries performed using a retrosigmoid approach. Rhomboid lips were classified according to thickness, extent, and appearance, with some subjected to histological analysis. T2-weighted magnetic resonance imaging of rhomboid lips was conducted. RESULTS: Among 304 surgeries, rhomboid lips were observed in 75 patients who underwent schwannoma or meningioma resection, facial spasm-related neurovascular decompression, and other surgeries (37, 2, 32, and 4 patients, respectively). Rhomboid lips were categorized based on apparent thickness: thin membranous type, resembling an arachnoid membrane, and thick parenchymal type. Rhomboid lip extension was classified by position relative to the choroid plexus: nonextension, lateral extension, and jugular foramen (41, 22, and 12 patients, respectively). Veins were observed on the rhomboid lip surface in 37 cases. The rhomboid lip was visible in only 1 case (parenchymal jugular foramen type) on magnetic resonance imaging. Histologically, the rhomboid lip comprised an ependymal cell layer, a glial layer, and connecting tissue. The glial layer thickness determined the rhomboid lip thickness, which was greater in the parenchymal type than in the membrane type. In 42 patients, the rhomboid lip was dissected with no complications observed. CONCLUSIONS: Morphological classification of the rhomboid lip and understanding of its anatomical details contribute to safe surgical field development for neurosurgeons.

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OBJECTIVE: Dysphagia is common in individuals who have undergone posterior fossa tumor (PFT) resection and negatively impacts on the individual's quality of life, nutritional status, and overall health. We aimed to quantitatively synthesize data from studies of the prevalence of dysphagia following PFT resection. METHODS: PubMed, Web of Science, the Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), Wanfang database, and VIP database were searched for case-control and cross-sectional studies that evaluated the prevalence of dysphagia after PFT surgery. Meta-analyses were performed to determine the prevalence of dysphagia. Subgroup and meta-regression analyses were performed to determine the sources of heterogeneity among the studies. RESULTS: A total of 22 studies were included, involving 20,921 cases. A meta-analysis of the random-effects model showed that the pooled global prevalence of dysphagia following PFT resection was 21.7% (95% confidence interval: 16.9-26.6). The subgroup and meta-regression analyses demonstrated that participant age (P < 0.001), assessment methods (P = 0.004), and geographical region of the study participants (P = 0.001) were sources of heterogeneity among the studies. CONCLUSIONS: Dysphagia has a high prevalence following PFT resection. Individuals with PFTs who are at a high risk for dysphagia should be identified early through screening. Multidisciplinary diagnosis and treatment of dysphagia are required to improve the outcomes in the early stages after PFT resection.

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