Medicine (RMH) - Theses
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ItemMobile and non-invasive devices as a diagnostic tool for physicians in detecting and classifying different seizure types( 2021)Introduction Epilepsy is one of the most common neurological disorders, affecting approximately 1 to 2% of the population. Epileptic seizures are caused by abnormal electrophysiological changes in the brain. In contrast, psychogenic non-epileptic seizures (PNES) are a class of seizures that are involuntary events, not caused by abnormal electrical discharges, but are thought to be a manifestation of psychological distress. The similarities in the observed behaviour between convulsive epileptic and convulsive psychogenic non-epileptic seizures (PNES) pose diagnostic difficulties. 20% of convulsive epileptic seizures are still misdiagnosed as PNES, delaying appropriate treatment for psychogenic seizures by an average of 5 to 7 years. This causes a poor prognosis and quality of life, as well as significant financial and social consequences. The current gold standard method to differentiate between the two is long-term Video Electroencephalography Monitoring (VEM), which is expensive and confined to few specialist centres. Therefore, a timely and accurate method of diagnosis outside the hospital setting is needed. Non-invasive and ambulatory devices are one such option being explored in this field, to not only detect convulsive epileptic seizures and PNES accurately, but also non-convulsive epileptic seizures. These devices typically measure physiological parameters such as 3-dimensional (3D) accelerometry, surface electromyographic signals (sEMG), heart rate, either separately or together, depending on the device. This approach is being recognised as automated seizure detection. This thesis aimed to investigate one such device, using 3D accelerometry, to differentiate between convulsive epileptic seizures and PNES. A further meta-analysis was conducted to quantify the accuracy of the devices, parameters and algorithms used in published studies for detecting all seizure types, including focal, generalised and psychogenic non-epileptic seizures Method In the first study, an off-the-shelf wireless, ambulatory device (Apple iPod) measuring 3D accelerometry was tested to investigate its sensitivity and false alarm rates for generalised tonic-clonic seizures (GTCS) and PNES. For this, consenting patients in the video-EEG monitoring (VEM) unit during their admission, were recruited, with the wireless device attached to their upper limbs. The data from the accelerometers went through an automated process using a machine learning algorithm, whereby convulsive activity detected was classified as a GTCS or PNES. The automated output for each seizure detected was compared to the corresponding VEM diagnosis to determine the device’s reliability using sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Cohen’s Kappa test. In the second study, a systematic review and meta-analysis was conducted involving two independent reviewers, to identify studies reporting the performance of mobile, non-invasive devices for the automated seizure detection of various seizure types. Limitations of these studies are acknowledged, and the directions for future studies are proposed. Results The overall finding of this thesis was that most non-invasive, ambulatory devices investigated for automated seizure detection have high sensitivities and acceptable false alarm rates for GTCS and PNES. This was evident in the first study where 13 PNES from five patients and 11 motor epileptic seizures were recorded during video-EEG monitoring. The sensitivity for detecting PNES and GTCS using 3D accelerometry was found to be 100% and 72.7%, respectively, with a FAR of 2.4 per 24 hours. The systematic review found that few studies have investigated the utility of ambulatory devices in the automated detection of focal seizures or the combination of both focal and GTCS. Moreover, the use of differing algorithms for each study, was found to increase heterogeneity. This implied that results between each study could not be directly compared, even when similar parameters were being used. This may hinder the ability to investigate these devices from moving to phase 4 studies where they may be tested in an out of hospital setting, the ultimate goal of utilising automated seizure detection. Conclusion The automated wireless device accelerometer tested in this study was shown to be sensitive in detecting and classifying both GTCS and PNES. There are a limited number of studies investigating the automated detection of focal seizures that are experienced by the majority of patients with epilepsy. The inability to compare studies due to the use of varied machine learning algorithms, may limit the use of such devices in phase 4 studies. It is essential that future studies involve larger population groups and determine automated detection for focal seizures. Furthermore, using pre-defined algorithms that have already displayed high sensitivities and low false alarm rates, particularly for the automated detection of GTCS and PNES, should be a priority for future research.
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ItemA Recipe for Disaster: Impact of extreme weather on nutrition and metabolic health, with a case study of Aboriginal and Torres Strait Islander communities in Northern Australia( 2019)BACKGROUND: To date, the effects of extreme weather events (EWEs) on specific nutrients within the population’s diet have not been quantified. With climate change projected to increase the severity of extreme weather across the globe, it is necessary to understand how the global nutrient supply has historically responded, and which subpopulations are most at risk. One particular subpopulation of importance is Aboriginal and Torres Strait Islander people, who are already more susceptible to nutritional insult and metabolic syndrome than their non- Indigenous counterparts. While extreme weather is not the primary driving force in poor health outcomes, I hypothesise that it further exacerbates cardiometabolic health burdens globally, and especially among vulnerable populations. METHODS: In my first study, I conducted superposed epoch analysis to calculate the percentage change in nutrient supply during the year of an EWE relative to its five-year window. I composited the results globally and by United Nations designated low-income subgroups. I also reported changes in terms of Recommended Dietary Allowance (RDA) for children aged 1-3 years. In my second study, I constructed a holistic model with data from 104 Aboriginal and Tor- res Strait Islander communities in the Northern Territory from 2010-2015. I used varimax- rotated Principal Component Analysis to extract and condense information from 218 variables for physical environment, census, and climate data. I then conducted MM-estimator regression to model the extreme heat impacts on cardiometabolic-related rates for emergency room, inpatient admission, primary healthcare, and mortality. RESULTS: In the first study, most micronutrient supplies exhibited modest negative percentage change during the year of an EWE, including folate, magnesium, niacin, phosphorus, potassium, thiamin, vitamin B6, vitamin C, and zinc. Effects were magnified among Landlocked Developing Countries, which exhibited significant nutrient supply changes ranging from 1.6 – 8.0% of average supply. The observed nutrient supply deficits were found to be a large percentage (up to 41.5%) of what a healthy child’s average sufficient dietary intake level should be. The most compelling finding of the second study is that holding all else fixed, a unit in- crease in climate PC1 score is associated with a 77.8% change in emergency room rates, 6.7 percentage point increase in inpatient rates, and 9.3 percentage point increase in primary healthcare rates. Thus, a larger cardiometabolic health burden is strongly correlated with communities that experience relatively lower apparent temperature and humidity but greater maximum heatwave severity, e.g. Alice Springs area. CONCLUSION: The EWE effects on nutrient supply are modest in isolation; however, in the context of nutrient needs for healthy child development, the effects observed are substantial. Children are a particularly vulnerable subpopulation of interest, given how certain nutritional deficiencies during gestation and the first five years of life can have irrecoverable consequences for health, growth, and development. In the second study, I found that relative heat – or sudden rises in temperature above that of the recent past – poses the most significant threat to cardiometabolic health among Indigenous communities in northern Australia. Relative heat, rather than absolute heat, should therefore be the focus of public health preparation and response. Both studies echo previous literature in stressing the urgency with which the international community must tackle the issue of nutritional and metabolic health among vulnerable populations, especially because this health landscape is poised to worsen with climate change.
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ItemManipulation of Natural Killer cells to improve stem cell transplant outcomes( 2019)Allogeneic haematopoietic stem cell transplantation (alloHSCT) is an effective and potentially curative treatment for many haematological malignancies due to its graft-versus-leukemia (GVL) effect. In order to achieve sustained engraftment after donor cell infusion, conditioning regimens before transplantation are required to deplete recipient immune cells. Myeloablative total body irradiation before transplantation is commonly used as an immunosuppressive method to allow recipients achieve donor cell engraftment. However, myeloablative conditioning (MAC) is organ toxic and tissue damage resulting from high dose of irradiation triggers pro-inflammatory cytokine release and inflammation inducing donor T cells activation, expansion then attack of host organs, which is defined as graft-versus-host disease (GVHD), the major complication and contributing factor to treatment-related mortality (TRM) after transplantation. Therefore, to improve prognosis and apply alloHSCT to patients who are not eligible for alloHSCT based on conventional intensive conditioning regimens, reduced intensity conditioning (RIC) was developed in recent years. Researchers have found patients with RIC treatment exhibited reduced TRM, but higher relapse rate compared to the MAC group, and results from experiments on mouse models revealed recipients that received RIC rejected the donor graft. In summary, although RIC has the potential to mitigate GVHD post-transplantation due to reduced toxicity to organs, it is insufficient to ensure sustained engraftment and GVL effect on its own. Previous studies have proven that the GVL effect is intertwined with GVHD, therefore it is a clinical aim to achieve a balance between the two, ensuring engraftment and tumor cell eradication, meanwhile mitigating complications and prolonging survival. RIC is less toxic to organs and has the potential to reduce GVHD but cause graft failure due to insufficient inhibition of the recipient immune system. Our previous study has found that Natural Killer (NK) cells were the primary residual cell population after reduced TBI, and more radio-resistant than CD8+ T cells in recipient mice. Mouse alloHSCT recipients with complete inhibition of NK cell cytotoxic function via perforin knock out exhibited rapid donor cell engraftment but early onset of acute GVHD. Moreover, NK cell adoptive therapy is becoming increasingly utilized as an anti-tumor immunotherapy, in addition to the supplementation of donor T cells in a HSCT scenario. Recent studies demonstrated infusion of donor NK cells is beneficial to promote donor cell engraftment and augment GVL effect while reduce GVHD by inhibiting alloreactive donor T cells and killing recipient APCs. Collectively, although RIC is less toxic to organs and has the potential to reduce GVHD, it is insufficient to deplete recipient immune cells resulting in graft failure after alloHSCT. Manipulation of recipient and donor NK cells combined with RIC using murine models allows us to explore the optimal method to maintain donor cell engraftment with preserved GVL effect and minimal GVHD, which may be further applied to clinical trials. We hypothesized that improved alloHSCT outcomes could be achieved using reduced intensity conditioning (RIC) in combination with pharmacological inhibition of recipient NK cells and introduction of donor NK cells to 1) promote engraftment; 2) reduce GVHD; and 3) exert GVL effect.
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ItemHereditary Haemorrhagic Telangiectasia: Genotype, phenotype and clinical practice( 2019)Hereditary Haemorrhagic Telangiectasia (HHT) is caused by pathogenic mutations in one of several genes, most commonly ENG, ACVRL1 or SMAD4. Characterised by dysregulated angiogenesis in multiple organs, it typically presents as bleeding from nasal telangiectasia and gastrointestinal arteriovenous malformations (AVMs). Lung, brain and liver AVMs are also common. As the genes causing HHT are integral to many fundamental cellular pathways additional to angiogenesis, it is likely that occult phenotypic features exist, but are incompletely explored. The studies described in this thesis aimed to document, explore and extend the phenotype of HHT in the Royal Melbourne Hospital HHT patient cohort, utilising basic disease pathophysiology to hypothesise the presence of additional occult phenotypic features, and to explore novel options for therapy. As Vascular Endothelial Growth Factor (VEGF) is known to be mechanistically involved in the abnormal angiogenesis of HHT, monoclonal antibody against VEGF has been used to treat epistaxis. Adverse reactions to systemic use have stimulated interest in topical intranasal administration, although results of previous studies have been mixed. We hypothesised that efficacy may be masked by nasal crusting, preventing the drug from reaching its target receptors. In a pilot open-label study (Chapter 2), topical Bevacizumab, when administered after standardised washout, reduced epistaxis severity. Given access to best care, HHT patients have normal longevity, but Quality of Life (QoL) may be overestimated. Using standardised tools, QoL assessment (Chapter 3) indicates significant disease impact, particularly on pain and discomfort. The propensity to develop AVMs in internal organs in HHT reportedly varies between the two commonest causative genes, ENG and ACVRL1. Lung AVMs are reported more commonly in ENG mutations, and central nervous system AVMs in ACVRL1 mutations. Disturbed angiogenesis may extend to aortic abnormalities. Analysis of aortic dimensions in HHT patients (Chapter 4), across the three most common HHT genes, revealed a limited association between SMAD4 mutation and proximal aortic enlargement. All HHT mutations result in perturbed TGF-Beta physiology, and TGF-Beta is integral to multiple immune system functions. While major immune disturbance is unlikely, decreased natural killer (NK) cell function could compromise normal immune surveillance capacity without being overtly obvious. NK cell function in HHT is explored in Chapter 5. Chapter 6 explores potential renal involvement in HHT, with no phenotype found. As the physiological link between BMP9 and ALK1 could predict disturbed calcification in HHT, circulating calciprotein particles were assayed. Beyond the sequencing of individual genes, Chapter 7 describes utilisation of massively parallel sequencing to attempt to define genotype in patients with classic phenotype but negative routine four-gene testing. Undertaking clinical research in rare diseases requires an understanding of patients’ perspective. Time constraints limit researcher-patient dialogue in the clinic, especially when multiple organ systems demand attention. The “family day” of Chapter 8 was designed to facilitate trilateral communication between patients, researchers and clinicians, and to evaluate its effectiveness.
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ItemShear wave elastography in the assessment of liver fibrosis( 2017)The accurate quantification of liver fibrosis is essential to the prognostication and clinical management of patients with chronic liver disease (CLD). Whilst liver biopsy remains the gold standard for fibrosis assessment, it has a number of limitations which have seen its use become increasingly substituted by non-invasive techniques. Ultrasound shear wave elastography (SWE) includes some of the most widely used non-invasive technologies in clinical practice. This work evaluates two ultrasound SWE devices which are in differing stages of clinical development and use; the first being a well-validated point SWE technique from Siemens called Acoustic Radiation Force Impulse elastography or ‘ARFI’ and the second a new 2D-SWE platform by Toshiba. The differing study aims for the two technologies were assessed in separate patient cohorts. Hence the thesis is divided in two. ARFI (Siemens): Background: Acoustic Radiation Force Impulse elastography or ‘ARFI’ is a point shear wave elastography (SWE) technique that is in broad clinical use for the quantification of liver fibrosis. Whilst well validated, questions remain for a number of areas of ARFI performance. This includes the magnitude and likely mechanism of obesity’s impact on ARFI performance, the impact of hepatosteatosis on ARFI reliability and whether ARFI performance is dependent on operator experience. There is also conflicting information as to whether ARFI liver stiffness measurements (LSMs) correlate with cirrhosis severity and the presence of cirrhotic complications. Finally, clinicians have limited facility to gauge the validity of obtained ARFI measurements beyond the IQR/Median criteria. An additional study aim was therefore to develop new strategies to aid ARFI reliability assessment; specifically whether inter-operator disagreement predicts the presence of unreliable ARFI measurements. Method: ARFI performance was assessed amongst a cohort of 943 patients with diffuse CLD of mixed aetiology, who had ARFI LSMs taken as part of clinical fibrosis assessment. Patients were scanned independently by either two or three operators, with ARFI results analysed in the context of patient demographic and CLD information obtained from medical records. Anthropometric measures including body mass index (BMI) was recorded at the time of scanning, and the distance from the skin surface to liver capsule (SLD) was measured from ARFI screenshots as a marker of central adiposity. The cumulative number of scans completed by individual operators and the institution overall was recorded. Assessed performance measures included IQR/Median and inter-operator agreement. ARFI accuracy was also assessed amongst a subcohort of 55 patients who had undergone a liver biopsy within 6 months of ARFI. The performance of ARFI in assessing cirrhosis severity was assessed amongst a further subcohort of 186 patients with clinically diagnosed cirrhosis. The presence of cirrhotic complications was determined retrospectively from medical records and endoscopy reports. Prognostic indices including Child Pugh and Model for End stage Liver Disease (MELD) scores were calculated using bloods tests where available. Results: ARFI showed modest accuracy in assessing liver fibrosis, demonstrating an AUROC of 0.67, 0.76 and 0.70 at discriminating the F01/ F2, F2/ F3 and F3/F4 cut-offs, respectively. ARFI showed good sensitivity (80.0 – 88.9%) and NPV (70.6 – 95.3%), but relatively poor specificity (42.9 – 66.3%) and PPV (27.9 – 56.2%) at the three cut-offs. Body habitus, particularly skin-to-liver capsule distance or ’SLD’, was found to be the primary determinant of ARFI performance in multi-regression analyses. SLD had the strongest relationship with ARFI accuracy (R2 = 0.543) followed by necroinflammatory change (R2 = 0.167), whilst all other patient factors, including hepatosteatosis, failed to show an independent association. Patients with a SLD >2.5cm (indicating significant central adiposity) showed particularly poor ARFI performance and was associated with higher IQR/Median ratios (median = 0.363 vs. 0.187, p<0.001), greater deviation between operators (29.8% vs. 15.9%, p<0.001) and poorer correlation with biopsy (rho = -0.242 vs. 0.493) than those with a SLD ≤2.5cm. Individual operator experience showed a weak relationship with ARFI performance, with operators of <25 scans experience having similar median IQR/Median ratios (0.170 vs. 0.165, p=0.13), slightly greater deviation between operators (14.3% vs. 11.06%, p=0.014) and greater deviation from the biopsy reference range (mean deviation = 0.588 vs. 0.279m/s, p=0.004) than more experienced colleagues. There also appeared to be a similarly weak association between overall institutional experience and ARFI performance, with reliability being slightly reduced amongst the first 150 scans performed in the institution. In patients in whom both operators had concordant F score results, ARFI LSM showed greater correlation with biopsy (rho = 0.392) than in cases of inter-operator disagreement (rho = 0.010). When scanned by three operators, patients with three-way operator agreement showed even stronger correlation with histopathology (rho = 0.571). Amongst cirrhotic patients, ARFI showed a moderately strong correlation with prognostic scores of liver function, including both MELD score (rho = 0.342, p<0.001) and Child- Pugh Score (rho = 0.363, p<0.001). ARFI LSMs showed modest accuracy in predicting the presence of ascites (AUROC = 0.58), encephalopathy (AUROC = 0.60) and oesophageal varices (AUROC = 0.69). Conclusion: ARFI showed moderate performance in quantifying liver fibrosis in a clinical Australian setting. The technology’s strength appears to be in the exclusion of liver fibrosis, however the tool is prone to false positive results. Body habitus was found to be the primary determinant of ARFI performance, with necroinflammatory change and operator experience showing a weaker impact on scan reliability. Central adiposity, as indicated by SLD, showed a particularly strong relationship with ARFI performance and the routine measurement and reporting of SLD should be considered to help clinicians gauge the reliability of ARFI results. Scanning patients with multiple independent operators also showed value as a reliability indicator, with inter-operator discordance being a predictor of poor ARFI performance. 2D-SWE (Toshiba): Background: The second technology assessed is a new 2D-SWE platform from Toshiba, which has a number of technical innovations and theoretical advantages over Siemens’ ARFI system. The technology is in the early clinical phases of testing and therefore data on this new technique remains limited. Our study aim was therefore to evaluate specific technical parameters to help assist in the formation of acquisition guidelines. This included assessing the measurement variability of Toshiba 2D-SWE (i.e. IQR/Median), the number of measurements required per patient to yield a precise LSM estimate and whether the uniformity of shear wave velocities within the measurement ROI (i.e. ROI SD/Speed ratio) could be used to assess the reliability of individual 2D-SWE measurements. Method: 2D-SWE was assessed amongst fifty-five patients with mixed aetiology CLD using the Toshiba Aplio 500 ultrasound system. Ten measurements were obtained per patient by an operator blinded to all preceding readings. Measurement variability (i.e. IQR/Median) and the number of measurements required per patient to achieve a LSM estimate within 5% of the existing method using 10 samples was assessed. Results were analysed against scan and clinical information including CLD aetiology, BMI, SLD, presence and severity of hepatosteatosis and measurement depth within the liver. The ratio of the standard deviation of shear wave velocities within the measurement ROI to overall shear wave velocity (i.e. ROI SD/Speed) was calculated for each individual measurement, and its relationship with measurement consistency (i.e. deviation of the measurement from the set’s median) was assessed. Results: The median IQR/Median ratio for 2D-SWE was 0.131 (q1-q3: 0.089–0.174). Five readings provided an approximation within 0.11m/s or 4.2% of the median velocity of ten measurements. Factors associated with increased measurement variability included increasing BMI (rho=0.388, p=0.003), SLD (rho=0.426, p=0.002) and measurements taken within 1.5cm of the liver capsule (p<0.001). Measurements with heterogeneous shear wave profiles (indicated by a ROI SD/Speed >0.15) showed greater deviation from the set’s median velocity than those with a ROI SD/Speed ≤0.15 (0.421 vs. 0.219 m/s, p=0.0001). Conclusion: 2D-SWE showed low overall measurement variability, with a minimum of five readings providing equivalent precision to the existing method using 10 samples. Obesity (i.e. BMI>30kg/m2), increasing abdominal wall thickness (i.e. SLD), sub-capsular measurements and a ROI SD/Speed >0.15 were all associated with increased measurement variability. ROI SD/Speed warrants further evaluation as a quality assessment metric, as it may allow objective operator assessment of individual 2D-SWE measurement reliability in real-time.
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ItemReducing acute respiratory complications in thoracolumbar spinal cord injury( 2018)Acute traumatic thoracolumbar spinal cord injury (TLSCI) is a devastating event, generally resulting in severe neurological deficits and often profoundly impacting respiratory function. Whilst relatively rare, each new case is associated with an average cost of 5.0 million Australian dollars over a person’s lifetime. Advancements in emergency, surgical and medical care now result in near-normal life expectancy after traumatic paraplegia in the developed world. Due to the ageing population, prevalence is projected to increase, further compounding the disease burden of TLSCI worldwide. Pneumonia is the dominant complication following TLSCI, particularly in the early weeks following injury. However, the prevalence of pneumonia in TLSCI is variably reported (2-31%) due to its dependence on diagnostic criteria. Pneumonia severity is generally proportional to the degree and duration of hypoxaemia and fever, both of which have been associated with elevated morbidity and mortality in central nervous system injuries, and therefore have the potential to inflict significant secondary spinal cord damage and negatively influence long term neurological outcome. Surgical timing, injury severity, neurological level of injury and comorbidity burden have been demonstrated in the literature to influence pneumonia development. Interventions aimed at preventing pneumonia in the acute hospital setting are resource-intensive and difficult to justify as a blanket intervention due to cost. The synthesis of a pneumonia prediction tool identifying a subset of patients at medium and high risk of pneumonia would provide opportunity for early, systematic and targeted interventions in a smaller group that have the greatest potential to positively respond. The overarching aim of this thesis is to improve the respiratory management of patients with TLSCI in the acute hospital setting. By exploring the timing of surgery and the complex interplay of other risk factors involved in clinically important pneumonia development, this thesis aims to develop a clinical prediction tool based on simple baseline factors, enabling early identification of high risk patients and subsequently facilitating resource allocation into prophylactic interventions in a smaller subset of individuals with TLSCI.
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ItemA systems biological investigation of mechanisms of seizure suppression by anti-epileptic drugs( 2017)Antiepileptic drugs (AEDs) remain the mainstay of intervention or treatment of epileptic seizures. There is still a lack of understanding about mechanisms of clinical AEDs. As seizures are an intrinsically network phenomenon, a ‘systems level’ analysis is required to understand drug mechanism of action. With this in vitro brain slice methodology, neuronal population activity as well as individual neuronal excitability and synaptic transmission were examined to provide a better understanding of seizure suppressive effects of individual and combinations of common AEDs.
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ItemCorrelation of the extent of ischemia assessed by aspects with post stroke seizures( 2016)Background: Ischemic stroke is a common cause of secondary seizures. Cortical involvement of ischemic stroke and large ischemic lesion size are amongst the most consistently reported risk factors for post stroke seizures. Alberta Stroke Program Early CT Score (ASPECTS) is a simple and reliable tool for quantifying the extent of cerebral ischemia and may function as a screening tool for patients at high risk of seizure development. We investigated the association of post stroke seizures with the extent of ischemia assessed by ASPECTS and with cortical involvement visualized on non-contrast CT. Methods: This cohort study was based on a prospectively maintained clinical database of acute ischemic stroke patients who were given intravenous tissue plasminogen activator treatment. We included patients with anterior circulation stroke admitted between January 2008 and October 2014. Patients with pre-stroke seizures were excluded. Clinical data and seizure follow-up data were collected. Non-contrast CT scans acquired both on admission and at 24 hours were analyzed. Logistic regression, survival analysis and receiver operating curve analysis were performed. Results: A total of 348 patients were included. The median age was 73 (inter-quartile range [IQR] 63-80) and 55% were male. During follow-up (median duration 559 days, IQR 107.5-1188.5 days), 22 (6.3%) patients developed post stroke seizures. Median time from stroke to seizure onset was 138 days (IQR 10-342 days). In univariate logistic regression, both ASPECTS on admission (odds ratio [OR] 0.69 per 1-point increase; 95% confidence interval [CI] 0.55-0.86; p=0.001) and at 24 hours (OR 0.80 per 1-point increase; 95% CI 0.70-0.92; p=0.002) were significantly associated with post stroke seizures. Cortical involvement at 24 hours also correlated with seizure occurrence (OR 3.01; 95% CI 1.08-8.34; p=0.03). Cox regression confirmed the higher risk of developing seizures at any time point in patients with lower ASPECTS value and cortical involvement. Of note, ASPECTS was the only independent predictor for post stroke seizures in multivariate logistic regression. Conclusion: The extent of ischemia assessed by ASPECTS and cortical involvement identified on non-contrast CT were associated with the development of post stroke seizures.
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ItemEffect of melatonin and indomethacin on adipose-derived stem cells and fat graft survival and function( 2016)Background: Autologous fat grafting has emerged as a key technique in soft tissue reconstruction, and is currently utilized for various deformities secondary to burns, chronic wounds, trauma, irradiation injuries and post-oncological resections. Nevertheless, a significant proportion of the transplanted fat fails to survive within the host environment, which may partly be attributed to cell death of its constituents. A process known as cell-assisted transfer is now used clinically to further enhance fat graft retention by adding stromal vascular fraction (SVF), an adipose-derived stem cell (ASC) rich content to lipoaspirate. However, there are certain concerns about cell-assisted lipotransfer especially regarding its oncologic safety and feasibility. Methods: The basis of this project stems from the need for reproducible and predictable clinical outcomes following transplantation of adipose tissue. To this end, the properties of two safe, commercially available and FDA-approved drugs, melatonin and indomethacin were studied. The in-vitro effects of melatonin on human ASCs were investigated through functional and survival assays including oxidative stress and cell-death assays, MTT Assay, monolayer scratch assay, cell membrane integrity assay, a human cytokine array, and a specific TNF-alpha ELISA kit. The in-vitro effects of indomethacin and melatonin on human ASC adipogenesis were investigated through a lipid (Oil Red O) staining kit as well as reverse transcription polymerase chain reaction (RT-PCR) to determine RNA expression of key adipogenic genes. The effects of melatonin-treated autologous fat grafts injected into the dorsums were tested in-vivo with a murine model, and its weights and volumes were assessed at three time points of two, four and twelve weeks. Hematoxylin and eosin staining, perilipin and CD31 immunostaining were performed with morphometric analysis of adipose tissue and vascularization. Results: The in-vitro results indicate that melatonin significantly protects human ASCs from hydrogen peroxide induced cell-death in a dose-dependent fashion. Addition of melatonin to ASCs improved cell-viability, promoted cell migration and preserved membrane integrity as compared to controls. In addition, it induced a potent anti-inflammatory response by down-regulating acute inflammatory cytokines particularly TNF-alpha but melatonin itself did not exert an adipogenic effect on human ASCs. Indomethacin stimulates adipogenesis of human ASCs in 2 weeks cell culture and upregulates several key adipogenic genes including PPAR-gamma, lipoprotein lipase and fatty acid binding protein 4. For the first time, this work demonstrated in-vivo that melatonin enhances fat graft volume retention at 4 weeks by increasing the percentage of adipose volume within fat grafts with comparable volumes to that of cell-assisted lipotransfer. Melatonin treatment, however, had no effect on angiogenesis. Based on these findings, melatonin and indomethacin may potentially be useful pharmacological adjuncts in clinical fat grafting based on their respective cytoprotective and adipogenic properties.
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ItemMinimally invasive deep brain stimulation via an endovascular stent-electrode array( 2016)Modern neural interfaces are practical demonstrations of what multi-disciplinary teams can create in this age of medicine. From decoding brain signals in order to control prosthetic limbs, to stimulating peripheral nerves in amputees to restore sensation, the blend of engineering and medicine continues to generate novel, life-changing, therapeutics. In an attempt to create a paradigm shift towards minimally invasive implantation of such neural interfaces, the Vascular Bionics Laboratory at The Royal Melbourne Hospital has designed a stent-electrode array that can be deployed in the cerebrovasculature via a series of percutaneously positioned catheters. While the device was designed to record brain signals for the purpose of decoding them, its stimulation capabilities had not been studied. This thesis takes that next step by conducting stimulation studies with the device. Were such a stimulation process established with these proof of concept experiments, then the device would hold promise for future neural interfaces. The animal model that the stent-electrode arrays had been designed for was used for these stimulation studies. Seven Corriedale sheep had devices implanted, and then a series of stimulation experiments were conducted across a range of time points using a variety of stimulation parameters and configurations while the animals were awake; the objective of stimulation was to excite the motor cortex and thereby induce a categorical response, such as the contraction of a limb. Stimulation parameters included monophasic, either anodal or cathodal, pulses at phase widths of 200 µs or 500 µs and at frequencies of either 20 Hz or 50 Hz with currents ranging from 1 to 6 mA. These were applied across a variety of configurations including monopolar, with either a head-mounted or flank-mounted return electrode, and bipolar. Pulse trains were also studied. Induced motor activity was documented principally by visual observation and accelerometer tracking. A range of motor activity was documented across the animals including about the flank, the neck, the ear, and some facial muscles. However, these contractions did not align to the neuroanatomical position of the electrodes relative to the motor cortex, nor were the contractions consistent across time points. In addition, the majority of contractions were not elicited from bipolar stimulation and thus prone to induction by current spread. Four devices were found on autopsy to have severed cables connecting to the stent-electrode arrays, a failure not identified by the regular tacking of impedances in the device. The dataset generated from these stimulation studies suggested that the motor activity documented was a product of current spread through the devices to muscles of the sheep, rather than motor activity caused by stimulation of the motor cortex. These studies serve to guide future experiments with this device.