1,720,983 research outputs found
The spectrum of mutatine for the diagnosis of vanishing white matter disease
No full textVanishing white matter disease (VWM; MIM #603896), also known as childhood ataxia with central nervous system hypomyelination (CACH) syndrome, is an autosomal recessive transmitted leukoencephalopathy related to mutations in each of the 5 genes (EIF2B1, EIF2B2, EIF2B3, EIF2B4 and EIF2B5) encoding for the 5 subunits of eukaryotic translation initiation factor 2B (eIF2B), essential for protein synthesis. VWM is characterised by ataxia, spasticity, variable optic atrophy and intermittent episodes of acute regression of clinical and neurological status. Another key step in diagnosis, besides clinical picture and gene sequencing, is magnetic resonance imaging (MRI), which typically shows a progressive rarefaction of the brain white matter, and its replacement by cerebrospinal fluid (CSF). In the present paper we summarise the up-to-date knowledge about VWM and include the full list of known mutations
Acquired Dandy-Walker malformation and cerebellar hemorrhage: Usefulness of serial MRI
No full textBackground/purpose Neuroimaging plays a fundamental role in the diagnosis of Dandy Walker malformation (DWM), a posterior fossa anomaly that is usually associated with genetic abnormalities, but may rarely be ascribed to acquired causes. Here, we report the clinical history and neuroimaging studies of a child with a complex cardiac malformation, developmental delay, and oculomotor anomalies whose neuroimaging findings were consistent with an acquired form of DWM. Methods/results Fetal MRI at gestational weeks 27 and 31 showed cerebellar and vermis hypoplasia and fourth ventricle enlargement, together with hemosiderin deposits on the cerebellar hemispheric surface, but without significant vermian rotation. Postnatal MRIs at 5 days and 13 months revealed progressive counter-clockwise rotation of the hypoplastic cerebellar vermis with cystic dilation of the fourth ventricle, eventually leading to a full-blown DWM. Conclusion This case strengthens the opinion that DWM is a heterogeneous condition, and may support the hypothesis that acquired meningeal abnormalities in the form of cortico-pial hemosiderosis may play a role in the development of DWM. This case also demonstrates that serial neuroimaging plays a key role in the correct diagnosis of posterior fossa malformations, whose prognosis is difficult to establish on second trimester fetal MRI and requires longer clinical follow-up
Circadian rhythms and measures of CNS/autonomic interaction
No full textThe physiological role and relevance of the mechanisms sustaining circadian rhythms have been acknowledged. Abnormalities of the circadian and/or sleep-wakefulness cycles can result in major metabolic disorders or behavioral/professional inadequacies and stand as independent risk factors for metabolic, psychiatric, and cerebrovascular disorders and early markers of disease. Neuroimaging and clinical evidence have documented functional interactions between autonomic (ANS) and CNS structures that are described by a concept model (Central Autonomic Network) based on the brain-heart two-way interplay. The circadian rhythms of autonomic function, ANS-mediated processes, and ANS/CNS interaction appear to be sources of variability adding to a variety of environmental factors, and may become crucial when considering the ANS major role in internal environment constancy and adaptation that are fundamental to homeostasis. The CNS/ANS interaction has not yet obtained full attention and systematic investigation remains overdue
Voxel-based assessment of differences in damage and distribution of white matter lesions between patients with primary progressive and relapsing-remitting multiple sclerosis.
No full textBACKGROUND:
Several studies have reported lower focal demyelination and inflammatory activity in primary progressive multiple sclerosis (PPMS) than in relapsing-remitting MS (RRMS). However, very little is known about possible differences in damage and distribution that may occur within lesions visible on magnetic resonance imaging in the 2 forms of the disease.
OBJECTIVE:
To evaluate differences in spatial distribution and structural damage of focal demyelinating lesions in patients with PPMS and RRMS.
DESIGN:
We acquired conventional magnetic resonance and magnetization transfer images in 24 PPMS and 36 RRMS patients (matched for sex, age, and disease duration) and 23 healthy sex- and age-matched controls. In each participant, we measured T2- and T1-weighted lesion volumes and magnetization transfer ratios in lesional and nonlesional brain tissues. The spatial distribution of focal demyelination was assessed using T2- and T1-weighted lesion probability maps in each patient group. Voxel-based procedures were performed.
SETTING:
University hospital.
RESULTS:
Patients with PPMS had greater disability than those with RRMS, with 70% of PPMS patients and 11% of RRMS patients having relevant motor symptoms. The T1- and T2-weighted lesion volumes were higher in PPMS than in RRMS patients (P < .001). T1- and T2-weighted lesion probability maps showed that the maximum probability for lesions was higher in PPMS (peak probability, 45% and 29%, respectively) than in RRMS (peak probability, 33% and 19%, respectively) patients and was localized in the corona radiata. Voxelwise analysis of lesional magnetization transfer ratios gave overlapping results.
CONCLUSIONS:
Differences in cerebral pathologic involvement exist between RRMS and PPMS and contribute to variations in clinical disability
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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