Saudi Cultural Missions Theses & Dissertations
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Item Restricted Exploring the Role of Biomarkers in Traumatic Brain Injury: A Review(Queen Mary University of London, 2024-08-12) Saddeek, Razan; Tranchida, VincentTraumatic brain injury (TBI), a global public health challenge lasting more than 3500 years, can be linked to a greater probability of morbidity and mortality. It may contribute to psychiatric and neurological diseases, making it a recognized incident of injury and a 'disease process'. TBI is categorized into two stages: primary injury and secondary injury, and it is categorized into three levels: severe, moderate, and mild. Clinical assessment of TBI patients includes neuroimaging, assessment of the patient's state of consciousness, pupil examination, and evaluation of the cranial nerves. However, these assessments do not provide enough detail about the underlying mechanisms of TBI. Biomarkers have been extremely beneficial in the development of a wide range of clinical conditions, such as those in the fields of cardiology, cancer, hematology, and infectious diseases. This research examines six biomarkers with potential as prognostic and diagnostic indicators of TBI. The biomarkers are S100B, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), tau, neurofilament light chain (NF-L), and ubiquitin c-terminal hydrolase-L1 (UCH-L1). These biomarkers are found in the blood and cerebrospinal fluid (CSF) of patients with TBI. The use of these biomarkers has shown their ability to assist in the early detection and assessment of disease severity, along with clinical prognosis after TBI. Furthermore, these biomarkers show a significant level of sensitivity in the detection of TBI, therefore limiting the need for unnecessary neuroimaging. This research also highlights the limitations and challenges associated with these biomarkers. Ultimately, the primary objective of this research is to provide a thorough understanding of traumatic brain injuries and their diagnosis using biomarkers.12 0Item Restricted Characterising Changes in Visual Attention Following Traumatic Brain Injury (TBI)(Saudi Digital Library, 2023-05-30) Alnawmasi, Mohammed; Khuu, SieuPurpose: Traumatic Brain Injury (TBI) is a major worldwide public health concern, with approximately 69 million individuals sustaining some form of brain injury annually. Though this figure is likely to be underreported as many do not seek medical treatment. Long-term changes in cognition and memory are sequelae of all brain injury severities and, most commonly as deficits in attention. Attentional processes are heterogenous and have been proposed to comprise different functional aspects or components that operate to deploy attention in different ways. For example, attention can be selective, divided, sustained and spatially allocated. However, it remains to be established whether TBI leads to a general deficit in attention or whether certain components are more affected. The thesis addresses this research question by focusing on visual attention using two approaches. First, behaviourally using two novel tasks (Motion tracking and a variant of Posner cueing) in which their stimulus conditions (such as duration and search efficiency) were systematically varied to assess different components of attention. And secondly, by observing changes in the allocation of visual attention through eye movement measurements and pupil responses (which are effective markers of attention) while performing these attentional tasks. Method: A systematic review and meta-analysis was initially conducted (Chapter 2) to provide an indication of the impact of TBI on visual attention and its components from the published literature. Drawing on the limitations and gaps in knowledge observed from this review, a series of cross-sectional studies were conducted that compared the performance of patients with mild TBI and normal participants on multiple conditions in which each task condition was used to assess a specific component of visual attention. Particularly, in Chapters 3 and 4, selective, divided and sustained attention was investigated using a multiple object tracking (MOT) task and varying stimulus parameters such as the number of targets to be tracked, the number of distractors and tracking duration. In Chapters 5 and 6, we investigated the allocation of attention using a modified Posner cueing task for conditions in which search efficiency and cue validity were systematically varied. Behavioural measures include sensitivity and reaction time and response-independent measures, including the pupillary response and eye movements. Results: Meta-analysis of previous works showed that the combined effect size of an attentional deficit following TBI is large but characterised by high heterogeneity. The latter finding highlights the potential impact of different dependent and independent variables on study outcomes. Additionally, there was a paucity of knowledge in understanding changes in divided and sustained visual attention following TBI. Chapters 3 and 5 contribute to knowledge by showing that patients with mild TBI exhibit a poor ability to orient visual attention (endogenously and exogenously) and in tracking multiple targets, particularly when the tracking duration was long and the number of to-be-tracked targets and the number of distractors was high. Chapters 4 and 6 showed that deficits in attention following mild TBI are also associated with deficits in eye movement measures (number of fixation and duration and tracking strategy) and pupillometry measures (latency and pupil amplitude), which is broadly indicative of a lack of attentional resources. Conclusion: Collectively, the results of this thesis showed a generalised visual attention deficit after TBI, which was not selective to a specific component of visual attention. Deficits in visual attention manifested in all outcome measures (including performance accuracy and reaction time), which suggests the importance of considering them in the assessment of visual attention. The cognitively driven pupillary response and eye movement patterns differentiated patients with mild TBI and might be considered an alternative measure of visual attention, particularly in the clinical population.34 0