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UBC Theses and Dissertations

The utilization and timing of neuroimaging and the role of neurophysiological techniques in the diagnostic evaluation of transient ischemic attack Edwards, Jodi Dawn


Background: Transient ischemic attack (TIA) is an episode of transient focal neurological deficit with an ischemic vascular cause. Neuroimaging can detect ischemia, determine etiologic mechanisms, and identify stroke risk after TIA, and early assessment reduces stroke risk. Despite guidelines recommending imaging, Canadian hospital-based studies have reported underutilization and delays in the use of imaging procedures after TIA. However, as many TIA patients are not evaluated in hospital, population-based studies are required to determine whether imaging use increased after guideline implementation and characterize trends in imaging timing after TIA. Although administrative databases enable population-based studies of procedure utilization and timing, previous studies have been restricted to hospital-based cohorts, as physician claims data lack validity for TIA ascertainment. Further, as many patients are not evaluated acutely, the assessment of alternative techniques may inform the subacute effects of transient ischemia. Methods: In Chapter 2, sensitivity, specificity, and positive predictive value were used to evaluate the validity of multiple algorithms for TIA case ascertainment from physician claims data. Chapters 3 and 4 provided estimates of imaging utilization before and after guideline implementation and trends in imaging timing in population-based TIA cohorts. Chapter 5 used transcranial magnetic stimulation to measure thresholds for intracortical inhibition and facilitation subacutely after TIA and assessed the relationship of these thresholds with clinical features of TIA. Summary of Findings: The algorithms for TIA ascertainment using physicians claims data evaluated in Chapter 2 were not valid, informing the case definition for subsequent population-based analyses. Chapter 3 showed increases in neuroimaging use but overall poor utilization after the implementation of practice guidelines, with differences by modality and diagnostic setting. In Chapter 4, no changes in imaging timing after TIA were observed over the study period. In Chapter 5, alterations in intracortical thresholds after TIA on transcranial magnetic stimulation were observed and correlated with clinical risk scores. Conclusions: This dissertation contributes new knowledge of population-based practices of the use and timing of neuroimaging after TIA and has implications for future research examining barriers for timely access to imaging techniques and the utility of alternative techniques in the diagnostic evaluation of individuals with TIA

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