1,721,048 research outputs found
Management of chiari malformation
No full textUnderstanding of the Chiari malformation type I (CMI) has evolved over time thanks to accumulated surgical experiences, neuroradiological refinements, and better comprehension of pathophysiology. CMI is defined as a descent of the cerebellar tonsils into the cervical canal due to a volumetric disproportion between the posterior fossa and cerebellar volumes. In more than one-third of cases, CMI is associated with syringomyelia, a cystic dilation of the spinal cord which leads to debilitating myelopathy. It has been demonstrated that both these conditions are associated with the obstruction of the cerebrospinal fluid flow at the level of the foramen magnum caused by the low-lying tonsils. Historically, different surgical approaches have been attempted to cure this condition, accounting for nearly 15 different surgical procedures. Nowadays, the most performed surgical procedure is the osteo-dural decompression of the posterior cranial fossa aimed to re-establish a free flow of CSF from the cranium to the spinal subarachnoid space. Although comprised of the spectrum of rare diseases, the diagnosis of CMI has strongly increased due to the large availability of MR scanners. While there is general acknowledgment that CMI is characterized by cerebellar tonsillar descent, an exhaustive and definitive definition of the illness is hardly available. As a consequence, patients with low-lying cerebellar tonsils can be labeled as CMI patients although often they are asymptomatic or present symptoms not strictly related to the CMI. Apart from imaging criteria, to make a diagnosis of CMI, it is imperative to discern if patient’s symptoms are related to the CMI. Unfortunately, symptoms vary widely and can often mimic or overlap other conditions. Similarly, tonsillar ectopia can also be associated with other developmental and acquired disorders (e.g., craniofacial syndromes, hydrocephalus, posterior fossa tumors, benign intracranial hypertension, cranio-cervical malformations) which must be ruled out. A correct clinico-radiological correlation is fundamental in modern management of CMI because it not only impacts on patient’s selection but also on an adequate surgical treatment to be offered. This chapter gives an ample overview on the most important clinical and radiological correlates of CMI showing modern pathophysiology bases, peculiarities, and pitfalls in diagnosis. Surgical approaches will be deeply explored through the analysis of surgical cases giving special emphasis to operative techniques, operative risks, complications avoidance, advanced neurosurgical procedures, and treatment efficacy. At the end, this chapter should be useful to both the novice reader, by reporting the most up-to-date information on the CMI, and to the expert surgeon by disclosing some debated surgical and clinical aspects
Comment
No full textThe third ventricle has historically represented one of the most challenging areas to access surgically, so that lesions directly harboring into the ventricular chamber or secondarily extending into it from adjacent areas have been approached by means of different transcranial routes. The aim of this work is to report our experience with the endoscopic endonasal approach in the management of a series of patients affected by craniopharyngiomas, extending into or arising from the third ventricle, evaluating pros and cons of this technique, also in regards of the anatomy and the pathology dealt with. During the period between January 2001 and February 2011, 12 patients, 9 male and 3 female (mean age 50.4 years; range 12-68) underwent an endoscopic endonasal approach for the treatment of a craniopharyngioma involving or arising from the third ventricle. According to the grade of involvement of the third ventricle, we identified three main ventricular growth patterns: (1) stalk-infundibulum; (2) infundibulum-ventricular chamber; (3) stalk-infundibulum-ventricular chamber. Though gross total removal was achieved in eight patients (66.7 %), in three patients (25 %) was possible a near total removal (> 95 %) and only in one case (8.3 %) tumor removal has been partial (< 50 %). The overall analysis revealed a rate of 77.8 % improvement of post-operative visual defects. Concerning the complications, we reported an overall CSF rate of 16.7 %; two patients developed a subdural hematoma that has been treated with a surgical drainage. One patient died after the occurrence of a brainstem hemorrhage. The endoscopic endonasal route provides a good exposure, especially of the sub- and retro-chiasmatic areas, as well as of the stalk-infundibulum axis, which represents, when directly involved by a lesion, a gate to access the third ventricle chamber. Despite this study reporting only a preliminary experience, it seems that in properly selected cases-namely tumors growing mostly along the pituitary stem-infundibulum-third ventricle axis-this approach could be advocated as a valid route among the wide kaleidoscope of surgical approaches to the third ventricle
Resection of supratentorial gliomas: the need to merge microsurgical technical cornerstones with modern functional mapping concepts. An overview
No full textAlthough surgery is not curative for the majority of intracranial gliomas, radical resection has been demonstrated to influence survival and delay tumor progression. Because gliomas are very frequently located in eloquent or more generally critical areas, surgeons must always balance the maximizing resection with the need to preserve neurological function. In this overview, we tried to summarize the recent literature and our personal experience about (1) the benefits and limits of using preoperative anatomical and functional neuroimaging (anatomical MRI, DTI fiber tracking, and functional MRI), (2) the issues to consider in planning the surgical strategy, (3) the need to thoroughly understand microsurgical techniques that enable a maximal resection (subpial dissection, vascular manipulation, etc.), (4) the importance of individualizing surgical strategy especially in patients with gliomas in eloquent areas (the role of neuropsychological evaluation in redefining eloquent and non-eloquent areas), and (5) how to use intraoperative mapping techniques and understand why and when to use them. Through this paper, the reader should become more familiar with a comprehensive panel of techniques and methodologies but more importantly become aware that these recent technical advances facilitate a conceptual change from classical surgical paradigms toward a more patient-specific approach
When a benign disease turns into disaster: a unique case of a surgically treated hemorrhagic sylvian fissure meningioma
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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