Diagnosis Of Posterior Fossa Tumors Research Articles

Infratentorial choroid plexus tumors in children: Case report and review of literature

Background: Infratentorial choroid plexus tumors are rare lesions in the pediatric population. At diagnosis, they most often present with signs of intracranial hypertension and cranial nerve deficits. The main objective of the surgery is total resection and the prognosis is favorable in most cases.Case Report: A 16-year-old boy with gait disturbance, headaches and left side hypoacusia had a diagnosis of posterior fossa tumor with hypertensive hydrocephalus. He underwent urgent placement of a ventriculoperitoneal shunt and subsequently microsurgery with gross total resection. At follow up, the patient was asymptomatic and without deficits.Conclusion: Choroid plexus tumors should be included in the differential diagnosis of posterior fossa tumors in childhood. Preoperative planning, choosing the best surgical approach and interruption of the lesion's vascular supply as the initial step of surgery are fundamental strategies for successful treatment.

The Diagnostic Efficiency of Quantitative Diffusion Weighted Imaging in Differentiating Medulloblastoma from Posterior Fossa Tumors: A Systematic Review and Meta-Analysis.

Medulloblastoma (MB) is considered the most common and highly malignant posterior fossa tumor (PFT) in children. The accurate preoperative diagnosis of MB is beneficial in choosing the appropriate surgical methods and treatment strategies. Diffusion-weighted imaging (DWI) has improved the accuracy of differential diagnosis of posterior fossa tumors. Nonetheless, further studies are needed to confirm its value for clinical application. This study aimed to evaluate the performance of DWI in differentiating MB from other PFT. A literature search was conducted using databases PubMed, Embase, and Web of Science for studies reporting the diagnostic performance of DWI for PFT from January 2000 to January 2022. A bivariate random-effects model was employed to evaluate the pooled sensitivities and specificities. A univariable meta-regression analysis was used to assess relevant factors for heterogeneity, and subgroup analyses were performed. A total of 15 studies with 823 patients were eligible for data extraction. Overall pooled sensitivity and specificity of DWI were 0.94 (95% confident interval [CI]: 0.89-0.97) and 0.94 (95% CI: 0.90-0.96) respectively. The area under the curve (AUC) of DWI was 0.98 (95% CI: 0.96-0.99). Heterogeneity was found in the sensitivity (I2 = 62.59%) and the specificity (I2 = 35.94%). Magnetic field intensity, region of interest definition and DWI diagnostic parameters are the factors that affect the diagnostic performance of DWI. DWI has excellent diagnostic accuracy for differentiating MB from other PFT. Hence, it is necessary to set DWI as a routine examination sequence for posterior fossa tumors.

Cerebellar pilocytic astrocytoma: Unusual presentation in a 3-year-old girl with classical imaging features

Pilocytic astrocytomas (PAs) are the most common pediatric primary brain tumor. They are World Health Organization Grade 1 tumors with an excellent prognosis. In children, the cerebellum, optic nerve chiasm, and hypothalamic region are the most common locations in that order. Clinically, cranial nerve palsies, symptoms of raised intracranial pressure, and ataxia are commonly seen. We present an unusual case of PA in a 3-year-old toddler with inability to walk. High index of suspicion is required for the diagnosis of posterior fossa tumors in this age group as they can deteriorate rapidly.

Added value of magnetic resonance spectroscopy for diagnosing childhood cerebellar tumours.

1 H-magnetic resonance spectroscopy (MRS) provides noninvasive metabolite profiles with the potential to aid the diagnosis of brain tumours. Prospective studies of diagnostic accuracy and comparisons with conventional MRI are lacking. The aim of the current study was to evaluate, prospectively, the diagnostic accuracy of a previously established classifier for diagnosing the three major childhood cerebellar tumours, and to determine added value compared with standard reporting of conventional imaging. Single-voxel MRS (1.5 T, PRESS, TE 30 ms, TR 1500 ms, spectral resolution 1 Hz/point) was acquired prospectively on 39 consecutive cerebellar tumours with histopathological diagnoses of pilocytic astrocytoma, ependymoma or medulloblastoma. Spectra were analysed with LCModel and predefined quality control criteria were applied, leaving 33 cases in the analysis. The MRS diagnostic classifier was applied to this dataset. A retrospective analysis was subsequently undertaken by three radiologists, blind to histopathological diagnosis, to determine the change in diagnostic certainty when sequentially viewing conventional imaging, MRS and a decision support tool, based on the classifier. The overall classifier accuracy, evaluated prospectively, was 91%. Incorrectly classified cases, two anaplastic ependymomas, and a rare histological variant of medulloblastoma, were not well represented in the original training set. On retrospective review of conventional MRI, MRS and the classifier result, all radiologists showed a significant increase (Wilcoxon signed rank test, p < 0.001) in their certainty of the correct diagnosis, between viewing the conventional imaging and MRS with the decision support system. It was concluded that MRS can aid the noninvasive diagnosis of posterior fossa tumours in children, and that a decision support classifier helps in MRS interpretation.

Values of the apparent diffusion coefficient in the differential diagnosis of tumors of the posterior fossa in the pediatric population of Colombia

Introduction: Posterior fossa tumors are common in the pediatric population and require adequate characterization by means of structural magnetic resonance imaging (MRI) and advanced MRI techniques to achieve an appropriate therapeutic approach. Objectives: To determine the usefulness of apparent diffusion coefficient (ADC) values for the differential diagnosis of posterior fossa tumors in the pediatric population treated at a reference hospital in Bogotá D.C., Colombia. Materials and methods: Diagnostic accuracy study carried out in 28 pediatric patients diagnosed with posterior fossa tumor between 2017 and 2019 at the Fundación Hospital de la Misericordia, a quaternary care institution. ADC values were measured and compared with histopathological diagnosis as gold standard, obtaining sensitivity, specificity, and positive and negative predictive values. Differences between medians were determined using the Kruskall-Wallis test. The p value between the quantitative ADC value and the gold standard was calculated using Pearson's chi-squared test, with a significance level of p&lt;0.05. Results: The mean age of the participants was 83.9 months (SD=57 months), and 64.28% of them were boys. Medulloblastoma was the most frequent tumor (39.29%). For the diagnosis of medulloblastoma, an ADC value of 0.6210x10-³mm²/s was established, obtaining a sensitivity and specificity of 81.82% and 76.47%, respectively. For the diagnosis of pilocytic astrocytoma, an ADC of 1.03x10-³mm²/s was determined, with a sensitivity of 66.67% and a specificity of 89.40%. Conclusions: ADC value is useful to classify and differentiate posterior fossa tumors in the Colombian pediatric population, showing an inversely proportional relationship with the tumor grade.

PAEDIATRIC POSTERIOR FOSSA TUMORS : AN EPIDEMIOLOGICAL AND ANALYTICAL STUDY AT TERTIARY CARE CENTRE IN EASTERN INDIA

Introduction: Posterior fossa is the commonest site of primary intracranial tumors in children, accounting for 45-60% of 1 all pediatric tumors . The aims and objectives of the study is to analyse the incidence, clinical features, surgical outcome and complications in paediatric patients with posterior fossa tumor. Material and Methods: The present study is a non-randomized prospective observational study, conducted in the department of neurosurgery, Bangur Institute of Neurosciences (B.I.N), IPGME &amp; R, Kolkata from January 2019 to December 2020. Sample size is 50. Observations &amp; Results: Out of 480 cases of total CNS tumors who presented in the study period, 96 cases(20%) were of paediatric posterior fossa tumors. Male dominance was seen i.e. 32 cases(64%). Most of them were in the age group 5-12 years i.e. 30 cases(60%). Headache and vomiting was the most common presenting complain present in 41 cases(82%). Fourth Ventricle was the most common location, 30 cases(60%) with Medulloblastoma being the most common tumor, 24 cases(48%). Brainstem involvement was seen in 22 cases(44%). Post-op hydrocephalus and cerebellar mutism were seen in 6 cases(12%) each. Overall mortality was 8%(4 cases). Conclusion: Posterior fossa tumors are critical brain lesions with signicant neurological morbidity and mortality. Early diagnosis of posterior fossa tumors is vital to prevent potential risks of Brain stem compression, herniation, hydrocephalus and death. With rapid advancement in radiology and the advent of modern therapeutic modalities, early diagnosis and treatment reduced the morbidity and mortality rate and improved prognosis among the patients.

A Diagnostic Algorithm for Posterior Fossa Tumors in Children: A Validation Study.

Primary posterior fossa tumors comprise a large group of neoplasias with variable aggressiveness and short and long-term outcomes. This study aimed to validate the clinical usefulness of a radiologic decision flow chart based on previously published neuroradiologic knowledge for the diagnosis of posterior fossa tumors in children. A retrospective study was conducted (from January 2013 to October 2019) at 2 pediatric referral centers, Children's Hospital of Philadelphia, United States, and Great Ormond Street Hospital, United Kingdom. Inclusion criteria were younger than 18 years of age and histologically and molecularly confirmed posterior fossa tumors. Subjects with no available preoperative MR imaging and tumors located primarily in the brain stem were excluded. Imaging characteristics of the tumors were evaluated following a predesigned, step-by-step flow chart. Agreement between readers was tested with the Cohen κ, and each diagnosis was analyzed for accuracy. A total of 148 cases were included, with a median age of 3.4 years (interquartile range, 2.1-6.1 years), and a male/female ratio of 1.24. The predesigned flow chart facilitated identification of pilocytic astrocytoma, ependymoma, and medulloblastoma sonic hedgehog tumors with high sensitivity and specificity. On the basis of the results, the flow chart was adjusted so that it would also be able to better discriminate atypical teratoid/rhabdoid tumors and medulloblastoma groups 3 or 4 (sensitivity = 75%-79%; specificity = 92%-99%). Moreover, our adjusted flow chart was useful in ruling out ependymoma, pilocytic astrocytomas, and medulloblastoma sonic hedgehog tumors. The modified flow chart offers a structured tool to aid in the adjunct diagnosis of pediatric posterior fossa tumors. Our results also establish a useful starting point for prospective clinical studies and for the development of automated algorithms, which may provide precise and adequate diagnostic tools for these tumors in clinical practice.

Clinicopathological spectrum of Intracranial Posterior Fossa Tumours and their Prognostic significance

Background: Intracranial Posterior fossa tumors are critical brain lesions with significant neurological morbidity and mortality due to limited space and involvement of vital brain stem nuclei and fourth ventricle. Early diagnosis of posterior fossa tumors is vital to prevent potential risks of Brain stem compression, herniation, hydrocephalus and death. Aim of the study: 1. To study the morphological spectrum of intracranial posterior fossa SOLs. 2.To determine the frequency of posterior fossa SOLs reported in the tertiary care center of Nalgonda district. 3. To correlate clinical presentation with histopathological diagnosis and assess prognosis, and compare it with national and international literature. Materials and Methods: The present study was a retrospective description study conducted at the Department of pathology, Kamineni Institute of Medical Sciences, Narketpalli over a period of 3 years starting from June 2015 to June 2018. During this period, histopathological analysis of all the intracranial posterior cranial fossa tumors was done, correlated with clinical and radiological findings and prognosis assessed. Result: In our study Posterior fossa tumors are predominantly seen in adults with peak incidence in fourth decade. In children majority of the tumors were reported below 5 years of age. Most common presenting symptom was head ache and vomiting. Most common tumor was Medulloblastoma in children and Schwannoma in adults. Most common location was Cerebello-pontine angle followed by cerebellum. Recurrence rates were higher for CP angle tumors due to difficult sub-total resection. Prognosis is good for patients with total resection of tumors. Conclusion: Posterior fossa tumours are critical brain lesions with significant neurological morbidity and mortality. With rapid advancement in radiology and advent of modern therapeutic modalities early diagnosis and treatment is possible in many cases. Histopathology remains the gold standard in diagnosing Intracranial Posterior fossa tumours and necessary for the formulation of further management after neurosurgery.

Magnetic resonance spectroscopy in posterior fossa tumours: the tumour spectroscopic signature may improve discrimination in adults among haemangioblastoma, ependymal tumours, medulloblastoma, and metastasis.

Assessing a posterior fossa tumour in an adult can be challenging. Metastasis, haemangioblastoma, ependymal tumours, and medulloblastoma are the most common diagnostic possibilities. Our aim was to evaluate the contribution of magnetic resonance spectroscopy (MRS) in the diagnosis of these entities. We retrospectively evaluated 56 consecutive patients with a posterior fossa tumour and histological diagnosis of ependymal tumour, medulloblastoma, haemangioblastoma, and metastasis in which good-quality spectra at short (TE 30ms) or/and intermediate (TE, 136ms) TE were available. Spectra were compared using the Mann-Whitney U non-parametric test in order to select the spectral datapoints and the intensity ratios that showed significant differences between groups of lesions. Performance of these datapoints and their ratios were assessed with ROC curves. The most characteristic signatures on spectroscopy were high choline (Cho) in medulloblastoma (p < 0.001), high myoinositol (mIns) in ependymal tumours (p < 0.05), and high lipids (LIP) in haemangioblastoma (p < 0.01) and metastasis (p < 0.01). Selected ratios between normalised intensity signals of resonances provided accuracy values between 79 and 95% for pairwise comparisons. Intensity ratio NI3.21ppm/3.55ppm provided satisfactory discrimination between medulloblastoma and ependymal tumours (accuracy, 92%), ratio NI2.11ppm/1.10ppm discriminated ependymal tumours from haemangioblastoma (accuracy, 94%), ratio NI3.21ppm/1.13ppm discriminated haemangioblastoma from medulloblastoma (accuracy, 95%), and ratio NI1.28ppm/2.02pmm discriminated haemangioblastoma from metastasis (accuracy, 83%). MRS may improve the non-invasive diagnosis of posterior fossa tumours in adults. • High choline suggests a medulloblastoma in a posterior fossa tumour. • High myoinositol suggests an ependymal lesion in a posterior fossa tumour. • High lipids suggest a metastasis or a haemangioblastoma in a posterior fossa tumour.

Role of Diffusion-Weighted MR Imaging in Characterization of Posterior Fossa Tumors

Background: Conventional MR imaging is essential for diagnosis and evaluation of the posterior fossa tumors Objectives: To assess the value of diffusion weighted imaging and apparent diffusion coefficient in making distinction between different histological types of posterior fossa tumors.&#x0D; Type of the study: Cross-sectional study.&#x0D; Methods: Brain MRI and DWI assessed 19 patients (12 female and 7 male) with MRI diagnosis of posterior fossa tumors. absolute ADC values of contrast -enhancing solid tumor region and ADC ratio of solid tumor to ADC of normal -appearing deep White matter were compared with histological diagnosis postoperatively .The mean ADC value and ratio were determined by using a 2-tailed T test. Results: In eight of medulloblastoma ,The mean ADC value was 0.67±0.14x 10-3 mm 2/s and ratio 0.86±0.19 , ependymoma (n=3), ADC value 1.09 ±0.14 x10 -3 mm 2 /s and ratio 1,43±0.13 , pilocytic astrocytoma (n=4) ADC value 1,72 ±0.27x10 -3 mm2/s and ratio 2.19±0.4, brainstem glioma (n=2) with ADC value1.18±0.06 x10-3mm2/s and ratio 1.64±0.08 , haemangioblastoma (n=1) with ADC value1.46x10-1mm2/s and ratio 1.87 , and meningioma with ADC value 0.72x10-3mm2/s and ratio 0.85. ADC values were higher in JPA than in ependymomas and medulloblastoma (P value &lt;o,o5).ADC ratio were also statistically significant difference among these three tumors type .&#x0D; Conclusion: calculation of apparent diffusion coefficient value in the solid enhancing portion of tumor seems to be reliable for differentiate between medulloblastoma at one end and , juvenile pilocytic astrocytoma (JPA) and ependymoma at other end as the former has ADC of &lt; 1 while other tumors have ADC value of &gt;1.

P16.21 Medulloblastoma in adult: a case report and literature review

Introduction: Medulloblastoma is an embryonic tumor mainly located at the level of structures derived from the myelencephalon. It is the most common malignant tumor in children with a prevalence of 15-20% of intracranial tumors. In adult constitutes less than 1% of encephalic tumors. Method: The authors report a case of a 34 years old woman, who started complaining of occipital headache with morning predominance that prompted several visits to general emergency, with no other focal neurological signs. The clinical and imagiological investigation revealed a left cerebellar hemisphere lesion with about 40 mm larger diameter, heterogeneous signal capture T2, with apparent implantation base on the tentorium and edema that determinated partial collapse of the IV ventricle. Meningioma, pilocytic astrocytoma, glioma, cerebellar abscess, hemangioblastoma and metastasis were considered in the diferential diagnosis. The patient underwent total excision of well-defined contours lesion with lower tentorial insertion. Results: Pathological examination was consistent with medulloblastoma with neuronal and glial differentiation, IV grade (WHO classification). Postoperatively she presented loca haematoma with associated edema, conditioning acute hydrocephalus. The patient was reoperated with hematoma drainage and placement of external ventricular drainage. She has a follow-up of 2 years, with no evidence of recurrence or tumor dissemination. Karnofski performance score of 100% Conclusions: Although Medulloblastoma is a relatively rare brain lesion it should be considered in the differential diagnosis of posterior fossa tumors. The diagnosis is histological only and in cases of a high grade lesions maximum excision is indicated, once complete recession is the strongest good prognostic factor in this pathology.

Cerebellar cystic ganglioglioma in an 8-year-old child

The authors report a child with a cerebellar ganglioglioma and large cyst. An 8-year-old boy presented with headache and ataxia. Computerized tomography and magnetic resonance imaging (MRI) studies demonstrated a large cystic component associated with intense contrast enhancement of a mural nodule in the left cerebellar hemisphere. A preoperative diagnosis of cystic astrocytoma was made. The tumor was removed via a midline suboccipital approach. Pathological examination of the tumor specimen revealed a ganglioglioma. The postoperative course was uneventful. There was no tumor recurrence on repeat MRI. At most recent follow-up, the patient was well. Although rare, cerebellar cystic gangliogliomas should be included in the differential diagnosis of posterior fossa tumors.

Time to diagnosis of paediatric posterior fossa tumours: an 11-year West of Scotland experience 2000–2011

Introduction. Brain tumours are the most common solid childhood malignancy accounting for 20% of all paediatric cancers. Of these, posterior fossa tumours comprise approximately 60–70% of all brain tumours in children. Several studies have estimated the median pre-diagnostic interval (PSI) of paediatric brain tumours as approximately 60 days. Objectives. The objectives of this retrospective analysis were to (a) identify the common presenting symptoms of posterior fossa tumours, (b) determine the time interval from the first attributable symptom to the radiological diagnosis of a posterior fossa tumour, (c) compare the West of Scotland with other international centres and (d) identify which factors correlate with outcome for these children. Materials and methods. A retrospective case note review of 69 children diagnosed with posterior fossa tumours from January 2000 to September 2011. Of the 69 children diagnosed during this period, complete data were available for 66 children (M:F = 31:35, Mean age (SD): 7.50 + 4.53 years). Results. Nausea and vomiting (75.8%), headaches (63.6%) and incoordination (51.5%) were recorded as the most common presenting symptoms followed by lethargy (28.8%), cranial nerve palsy (25.8%) and diplopia (24.2%). Fifty-three of the sixty-six children (i.e., 80.3%) demonstrated radiological evidence of hydrocephalus on their initial scan. The majority of children were assessed by less than three specialists after a median PSI of 43.5 days. The only variable significantly associated with PSI was tumour grade (r = − 0.202, p = 0.036). Neither age at diagnosis, number of specialists seen, nor outcome was significantly correlated with PSI. The only factor associated with outcome was tumour grade (r = 0.337, p = 0.006). Conclusion. Despite recent reports indicating poor performance of the UK with respect to time to diagnosis of paediatric brain tumours, the present data indicate that the experience of this cohort is favourably comparable to international standards.

Galectin-3 expression: a useful tool in the differential diagnosis of posterior fossa tumors in children

Galectin-3 (Gal-3) is a glycan-binding protein highly expressed in several tumors, including brain neoplasms. This protein has been demonstrated to be correlated with adverse prognosis in some tumor types. However, the role of Gal-3 in pediatric posterior fossa tumors (PPFTs) has not yet been fully addressed. The goals of this study were to evaluate Gal-3 expression in a series of PPFTs and verify whether this expression is related to patient outcome. Gal-3 expression was analyzed by immunohistochemistry in 42 cases of surgically resected primary PPFTs. Surgeries were performed in our institution from January 2003 to December 2006. Tumor samples consisted of 21 pilocytic astrocytomas (PAs), 13 medulloblastomas, 4 ependymomas, 2 diffuse cerebellar astrocytomas, and 2 atypical teratoid/rhabdoid tumors (AT/RTs). All PAs and ependymomas strongly showed Gal-3 expression, whereas no immunostaining was observed in medulloblastomas and diffuse astrocytomas. In AT/RTs, Gal-3 expression was conspicuous but heterogeneous, being mainly observed in rhabdoid cells. Concerning the Gal-3 expressing tumors, no relationship was observed between the degree of expression and patient survival. Gal-3 was strongly expressed in reactive astrocytes, normal endothelial cells, and macrophages in the adjacent non-neoplastic brain parenchyma. Interestingly, the endothelial cells in the tumor bulk of PAs lacked Gal-3 expression. Gal-3 is differentially expressed in PPFTs, but its expression shows no correlation with patient outcome. However, the evaluation of Gal-3 is helpful in establishing a differential diagnosis among PPFTs, especially between PAs and diffuse astrocytomas, and in some circumstances between medulloblastomas and AT/RTs.

Posterior fossa tumors in children: how long does it take to establish the diagnosis?

The aim of this study is to evaluate, for our patient population, the time interval from the first chart-documented symptom to the radiological diagnosis in children and infants with posterior fossa tumors. We retrospectively analyzed 50 consecutive children (36 men, 14 women) with posterior fossa tumor treated at our department between January 1999 and December 2003. The mean age at time of diagnosis was 98 months (6 months-16 years). The mean follow up was 27 months (6-61 months). The diagnoses included astrocytoma (n = 17), medulloblastoma (n = 15), ependymoma (n = 6), and other tumors (n = 12). The mean time interval between onset of symptoms and radiographic diagnosis was 142 days (5-535 days), the median was 59 days. The mean time for Grade I and II tumors was 238 days (n = 19) and for tumors Grade III and IV 117 days (n = 31). The most common presenting symptoms were headache, nausea, vomiting, ataxia, and oculomotor deficits. Approximately half of the patients were initially diagnosed and treated for other diseases (gastrointestinal infection, appendicitis, psychological behavioral problems, cervical spine strains, different ophthalmologic entities). Specialists (ophthalmologists, orthopedics) tended to diagnose and treat their specific diagnoses (e.g., strabism, torticollis). Parents play a significant role in the process of establishing the correct diagnosis. We conclude that further information and education regarding symptomatology and diagnosis of posterior fossa tumors in children is necessary. Communication has to be improved between parents and referring physicians of all specialties and neurosurgeons.

Posterior cranial fossa tumours in children at Kenyatta National Hospital, Nairobi

The management of children with posterior fossa tumours is a challenge to health care professionals worldwide. Difficulties in diagnosis especially in children less than three years is well documented. Limited diagnostic modalities and lack of awareness of the symptoms and signs as well as societal perception of children's complaints contributes to late presentation. Kenyatta National Hospital Neurosurgical unit is the only specialized unit among the public hospitals in Kenya where such patients are referred. To review the management of posterior fossa tumours in children at Kenyatta National Hospital. A retrospective analysis of children treated for posterior fossa tumours at the neurosurgical unit of Kenyatta National Hospital between 1996-2003. Neurosurgery unit, Kenyatta National Teaching and Referral hospital. Thirty seven children were treated for posterior fossa tumours between 1998 and 2003. Twenty four were females while thirteen were males giving a male: female ratio of 1:1.8. The age varied between 2-16 years with a mean of 6.7 years. Cerebellar symptoms were the most common mode of presentation (30%) followed by headaches and vomiting. Twenty percent of our patients were blind at presentation probably due to chronic effects of raised intracranial pressure. Out of 11 patients with histological diagnosis of meduloblastomas, over 99%, were females and only one was a male. Astrocytomas were evenly distributed at five males and six females. The mean duration of symptoms was 3.7 months while it took eight weeks between time of diagnosis and treatment. Posterior fossa tumours in our set-up are more common in females than in males, M:F ratio of 1:1.8. Over 90% of medulloblastomas are found in female children making it a predominantly female tumour as opposed to available literature. The delay in diagnosis is probably due to lack of information both to the parents and health care providers and expensive diagnostic tools. A high index of suspicion, and a good history and clinical examination is required in the diagnosis of posterior fossa tumours in children especially those below three years.

Diagnosis of posterior fossa tumors with angiography in children.

The differential diagnosis of posterior fossa tumors with cerebral angiography in children is presented with diagrams and illustrations. The literature is reviewed and the angiographic landmarks are discussed. The advantage of this form of examination over other methods of contrast studies is emphasized. It is concluded that the detailed analysis of the angiographic findings in posterior fossa tumors in children can be of localizing and of diagnostic value in the majority of cases, and surgery can then be, performed without additional contrast studies.

Posterior fossa aneurysms simulating tumours.

Seven cases of aneurysm of the vertebral and basilar arteries, in which the clinical features suggested a diagnosis of posterior fossa tumour, are presented. Their clinical manifestations and the difficulties of diagnosis are discussed. These lesions may mimic cerebellopontine angle tumours or brain-stem gliomas, or, less commonly, the picture is one of a compressive lesion at the foramen magnum. The need for vertebral angiography is emphasized. Exploratory surgery carries a high risk, and is to be avoided.

Arteriovenous malformations of the posterior fossa.

Arteriovenous malformations of the posterior fossa are uncommon and are, therefore, not often considered in the differential diagnosis of posterior fossa tumors or subarachnoid hemorrhage. Verbiest (17) found 108 cases reported in the literature up to 1961. We have located an additional 29 since that report (2–4, 8, 9, 13, 14, 16, 18, 19), of which only a few were demonstrated by angiography. We are herein presenting the angiographic findings in 8 patients with malformations of the posterior fossa. These patients were examined either in Stockholm at the Serafimer Lasarettet and at the Neuroradiologic Department of the Karolinska Sjukhuset, or in San Francisco at the University of California Medical Center. Dural arteriovenous malformation of the posterior fossa and anomalous communications between branches of the occipital artery and the intradural sinuses have been reported separately (11, 12) and are not included in this report. Clinical Findings (Table I) All 8 patients were males, from eight to forty-...

Encephalography in diagnosis of posteriorfossa tumours.

Encephalography in diagnosis of posteriorfossa tumours.