Abstract TP166: Changing Trends In Imaging Of Neurological Complaints In Young Adults And Impact On Stroke Incidence

Introduction: Incidence of ischemic stroke in young adults is increasing, but reasons for this change remain unclear. One potential explanation may be increased detection of stroke due to increased use of brain MRI imaging. Methods: We performed a retrospective cohort study of adults ages 18-55 who presented to a large, multicenter health system from 1/1/2012-12/31/2018 with predefined focal neurologic chief complaints. Total counts of ischemic strokes based on ICD 9/ICD 10 code and total counts of MRIs were examined. Probability of ischemic stroke conditional on MRI and probability of MRI conditional on ischemic stroke were calculated. Counts were analyzed with Poisson/negative binomial count models and probabilities were analyzed with relative risk. Results: A total of 118,486 unique encounters were identified. Of these encounters, 1,179 (0.01%) led to ischemic stroke diagnosis and 8,293 (7.0%) had MRI brain ordered. Sixty-two percent of the encounters and the same proportion of MRIs were in females, but only 50% of ischemic strokes were in females. The probability (risk) of ischemic stroke diagnosis conditional on MRI was estimated to decrease by a proportion of 4.24% per year (95% CI: (0.91%, 7.24%), p value=0.013) (Figure). Yearly percent change from 2012 to 2018 of MRIs ordered and ischemic strokes followed a similar trend. Conclusion: The decreasing proportion of ischemic strokes diagnosed when MRIs were ordered suggests that the threshold for ordering MRIs in young adults with focal neurologic symptoms has decreased. Therefore, some of the increased incidence of stroke among young adults may be explained by increased use of MRI.