1,720,958 research outputs found
Variations in the circulus arteriosus cerebri in a South African cadaveric sample
Full text linkThe circulus arteriosus cerebri (CAC) or Circle of Willis is a highly variable arterial system at the base of the brain that allows for collateral blood flow, granting a protective effect during ischaemic events. Owing to variations, it may not compensate sufficiently during such events. Some CAC variations have been associated with aneurysm formation with subsequent rupture and subarachnoid haemorrhage. It is important to know the prevalence of these variations in a population. This is a cross-sectional, observational and quantitative study approved by the UCT Human Research Ethics Committee (645/2022) and the Cadaver Research Governance Committee (2022/009) in the Department of Human Biology. The brains of 94 bodies were analysed. Patency of hypoplastic arteries was investigated and Fiji® software was used to measure the lengths and diameters of arteries. Brain volumes were compared to arterial lengths and diameters and a correction factor for human variation was determined. The intact samples (n=40) were classified according to the 5-group system of Ayre et al. (2021) and 22.5% of the sample displayed the conventional anatomical pattern. The most common pattern of variation was group 5, comprising 15 different variations not matching the descriptions of groups 1-4. Individual variations were observed (n=64 brains; 81 variations). The most frequent variations were posterior communicating artery hypoplasia (17.3%) and aplasia (14.8%). The anterior communicating artery was the most variable artery (44.4% of individual variations). The narrowest artery was usually the right posterior communicating artery (PcoA) and the artery with the greatest variation in diameter was the left PcoA. Statistically significant associations were found for arterial diameter with age and length with age. Associations that were not statistically significant included variations with age, variations with sex and arterial dimensions with sex. There were too few intracranial aneurysms to perform analyses. These variations may result in an increased risk and severity of stroke and intracranial aneurysm formation. Knowledge about CAC variations will aid neurosurgeons when planning and executing a range of neurosurgical procedures. There is little published data on this topic in a South African setting and further studies are recommended
A morphometric study of the brain ventricles of patients diagnosed with Chronic Hydrocephalus at Groote Schuur Hospital
Full text linkHydrocephalus (HCP) is a cerebrospinal fluid condition of the central nervous system, which when it accumulates causes an increase in ventricular enlargement and raised intracranial pressure (ICP). Raised intracranial pressure in a fixed volume space is dangerous as it presses onto the brain parenchyma and the surrounding areas and may damage them. Ventricular enlargement is a radiological indicator of hydrocephalus and has been one of the features used to diagnose the condition, with the ICP measurement used to confirm the condition. However, measuring ICP is invasive and puts the brain at risk of bleeding and infections, making it necessary to use non-invasive methods of confirming the condition. This study aims to investigate the clinical features observed on the brain scans of patients with hydrocephalus and seeks to describe the unique shape of the frontal horns and use this shape as a noninvasive diagnostic marker. The study observed the brain magnetic resonance imaging and computed tomography scans of 150 patients who were suspected or known to have hydrocephalus from the Radiology Department at Groote Schuur Hospital. These scans were then divided into three groups, namely, the controls, and chronic and acute hydrocephalus groups. The clinical features commonly observed on the brain scans of patients with hydrocephalus were evaluated, their measurements taken, and their shapes recorded. These features were the Evans Index, temporal horn width, third ventricle width and shape, callosal angle, frontal horn shape, Sylvian fissure width and periventricular white matter changes. This morphometric data was then analysed to determine their relationship with hydrocephalus. Of the clinical features, the frontal horn shape has not been described in the literature. Therefore, it was described in this study, and its association with the measurement of ICP was assessed. There was a statistically significant difference in the morphometric data between the control and chronic HCP groups. In contrast, the difference in the data between the chronic and acute HCP groups was not statistically significant. In all three groups, there was a difference in size between the left and right sides, the right side had smaller measurements than the left. There was a significant difference in frontal horn shape between the chronic and acute HCP groups. Additionally, it was evident that there was a relationship between a specific shape of the frontal horn and the measurement of ICP. The morphometric data of the clinical features were consistent with the literature, except for the Sylvian fissure width. The data in this study showed that the accumulation of CSF occurred mostly on the left side in the clinical features that compared the sides, perhaps suggesting that the condition favoured the left side. The frontal horn shape was different in the chronic and acute HCP groups, it was described as quadrilateral and round, where the quadrilateral shape correlated with the low-moderate ICP, and the round shape correlated with the high ICP reading. Therefore, the frontal horn shape has the potential to be used in the clinical space as a non-invasive imaging marker when differentiating between chronic and acute HCP patients
The prevalence of anatomical variations in the intraorbital part of the ophthalmic artery and its branches in cadavers
No full textEnglish: The human orbit contains various important structures that may show variations relating to
their anatomy. This study focused on the intraorbital part of the ophthalmic artery in a South
African cadaver sample in the Free State (UFS) and Western Cape provinces (UCT).
Meyer pioneered the study of the ophthalmic artery as far back as 1887, with a main focus
on its branches and their variations. Very limited investigation has been carried out in this
field and available literature has little information on this. Currently no published data exists
on the South African population with regard to intraorbital variations within the ophthalmic
artery and its branches.
Original research was conducted to address the problem of the lack of data. Dissections of
the eyes were done to investigate and document the possible variations of the intraorbital
part of the ophthalmic artery and its branches.
The aim of the study was to determine the prevalence of anatomical variations in the
intraorbital part of the ophthalmic artery and its branches in a cadaver sample. The results of
the study will be of value to surgical interventionists treating patients with vascular diseases
within the orbital region and also to the ophthalmology students studying the orbital vascular
anatomy.
A total number of 59 cadavers were utilised, and 118 eyes were dissected under the lighted
magnifier and observed for variations. The sample consisted of 23 cadavers (46 eyes) from
the Department of Basic Medical Sciences of the University of the Free State, and 36
cadavers (72 eyes) from the Department of Human Biology of the University of Cape Town.
Sixteen types of variations were observed and documented.
The ophthalmic artery crossed below the optic nerve in the left eye in 7.63% of cadavers at
both institutions. No ophthalmic artery crossed below the optic nerve in the right eye in the
UCT group, whereas 17.39% in the UFS group crossed below the optic nerve. Statistical
analyses determined the frequencies of the variations. In certain individuals there were more
than one type of variation which is in agreement with published literature. The majority of
variations in branching patterns occurred bilaterally and in most cases, the variation in the
left eye differed from the variation in the right eye. Males showed a higher frequency of
variations.
These findings may well contribute to clinical application in ophthalmology and radiology
while it will also inform anatomy students studying the blood supply to the eye and
surrounding structures.Afrikaans: Die menslike oog bevat verskeie belangrike strukture wat moontlik variasies kan toon wat
verband hou met hul anatomie. Hierdie studie fokus op die intraorbitale deel van die
oftalmiese arterie in ʼn Suid-Afrikaanse kadawersteekproef in die Vrystaat (UV) en die Wes-
Kaapse (UCT) provinsies.
Meyer was alreeds in 1887 die voorloper van studies van die oftalmiese arterie en het veral
gefokus op die vertakkings en hul variasies. Slegs beperkte ondersoeke op hierdie terrein is
gedoen en beskikbare literatuur bevat min inligting oor die onderwerp. Tans is daar geen
gepubliseerde data beskikbaar oor die Suid-Afrikaanse bevolking met betrekking tot
intraorbitale variasies binne die oftalmiese arterie en sy vertakkings nie.
Oorspronklike navorsing is gedoen om die probleem van die gebrek aan data aan te spreek.
Disseksies van die oog is uitgevoer om die moontlike variasies van die intraorbitale deel van
die oftalmiese arterie en sy vertakkings te ondersoek en te dokumenteer.
Die doel van die studie was om die voorkoms van anatomiese variasies in die intraorbitale
deel van die oftalmiese arterie en sy vertakkings in ’n kadawersteekproef te bepaal. Die
resultate van die studie sal waardevol wees vir chirurge wat intervensies doen op pasiënte
met vaskulêre siektetoestande binne die orbit en ook vir oftalmologiestudente wat die
anatomie van die orbit bestudeer.
In totaal is 59 kadawers bestudeer en 118 oë is gedissekteer onder ’n verligte vergrootglas,
en die variasies is waargeneem. Die steekproef het bestaan uit 23 kadawers (46 oë) van die
Departement Basiese Mediese Wetenskappe van die Universiteit van die Vrystaat (UV) en
36 kadawers (72 oë) van die Departement van Mensbiologie van die Universiteit van
Kaapstad (UCT). Sestien tipes variasies is waargeneem en gedokumenteer.
Die oftalmiese arterie van die linkeroog het in 7.63% van kadawers van beide instansies die
optiese senuwee onder gekruis. Geen oftalmiese arterie het onder die optiese senuwee in
die regteroog gekruis in die UCT groep nie, terwyl dit in 17.39% van die UV groep
voorgekom het. Statistiese analises het die frekwensie van die variasies bepaal. By
sommige individue was daar meer as een tipe variasie, wat in ooreenstemming is met
bevindinge in gepubliseerde literatuur. Die meerderheid variasies in vertakkingspatrone het
bilateraal plaasgevind en in die meerderheid gevalle het die variasie in die linkeroog verskil
van die variasie in die regteroog. Manlike persone het ’n groter frekwensie van variasie
vertoon.
Hierdie bevindinge mag inderdaad bydra tot kliniese aanwending in oftalmologie en
radiologie terwyl dit ook anatomiestudente wat die bloedtoevoer tot die oog en omliggende
strukture bestudeer van inligting voorsien.UFS (M) Research Bursary 2016DHET through nGAPNational Research Foundation (NRF)UFS Health Sciences Bursary 201
Variations in arterial supply via the external and internal carotid arteries to the bony orbit and eyeball in full-term fetuses, infants, children, adolescents, and adults – a South African perspective
Full text linkThe anatomy of the orbital region is of great importance for many highly specialised clinical disciplines such as ophthalmology, maxillofacial surgery, and neurosurgery. The main source of arterial blood supply to the orbital region is by the ophthalmic artery, a branch of the internal carotid artery, and to a lesser extent by the anastomotic patterns which are formed through the external carotid artery. A range of arterial variations which may be developmental in origin, or which may develop due to pathologies later in life, may affect the ophthalmic artery in terms of its origin, course, and branching. If clinicians are not aware of the variations occurring in this region, the eye of the patient may be at risk of injury during invasive procedures, which may lead to partial or complete visual loss. Up until the present time, there have been only a few cadaveric studies that revealed some of the variant patterns and the overall frequencies of the recorded anastomotic patterns for the orbital blood supply. Whilst the anatomical variations are known, the frequencies of variations in the population are not. Furthermore, no published data exists regarding the variations in the orbital blood supply in a South African population. Therefore, the aim of this study was to investigate the orbital vascular supply within the South Africans of different age groups, to document and describe any variations in anastomotic patterns and record their frequencies. The current study was conducted through dissections of bodies in the Department of Human Biology, University of Cape Town, and patients' angiograms from Groote Schuur Hospital. The angiograms included data obtained from other hospitals within the Cape Town area and were reviewed retrospectively. The dissection sample included six full term fetuses and 63 adults, and the angiograms accounted for 870 individuals. The ophthalmic artery was studied from the point of origin from the internal carotid artery and its course in relation to the optic nerve, and both sides were compared to note any similarities or differences. Statistical analyses were performed to record the frequencies of the patterns of variations and to note whether there were any associations between sex, age, sidedness, and these variations. The results revealed statistically significant associations between age and sex for the patterns of variation. Several variations were noted in the current study. Among the novel findings were those in the origin of the ophthalmic artery from the internal carotid artery, whereby a lateral and inferior origin were recorded in both samples (dissected bodies and angiograms). In addition, it was noted that the ophthalmic artery may take origin from the A2 segment of the anterior cerebral artery, which is also a novel finding. This study, therefore, adds significantly to the current body of knowledge regarding the patterns of arterial supply to the ophthalmic region in a South African sample
A dissection and angiographic study of anatomical variations in the anterior communicating artery complex in a South African sample
Full text linkThe anterior communicating artery complex (ACAC) consists of the A1 and A2 segments of the anterior cerebral artery (ACA) and the anterior communicating artery (ACoA). The ACAC is said to be the most frequent site of aneurysms and anterior cerebral circulation variations. Clear correlation between cerebral arterial circulation variations and aneurysm development has been reported. Cerebrovascular diseases play a significant role in the causes of morbidity in South Africa. South African data in this area of research is currently lacking and thus more knowledge is needed. This study aims to report the prevalence of variations in the ACAC and their link to the prevalence of cerebral aneurysms. For the dissection portion of this study, a total of 68 (35 female and 33 male) adult formalin fixed brains were included. These brains were from the bodies that were previously dissected in the Department of Human Biology, University of Cape Town by the medical undergraduate and honours post-graduate students. For the an
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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