Cryptogenic stroke: Frequency and diagnostic evaluation across different age groups

Abstract

Introduction: Stroke etiology differs across the age spectrum, with higher rates of uncommon causes in younger adults, and large-artery atherosclerosis or cardioembolism in older adults. There is little data regarding frequency of cryptogenic stroke (CS) across the age spectrum. Conceivably, CS frequency may differ across age groups because of differences in extent of diagnostic tests, and diagnostic yield (i.e. abnormal result relevant to stroke etiology). Methods: We retrospectively analyzed our stroke registry data with consecutive inpatients with imaging-confirmed ischemic stroke/TIA admitted 2007-2010. Stroke etiology was prospectively classified by trained MDs into TOAST categories using an automated algorithm. Patients were grouped according to age, 18-49y, 50-75y and 75+ years. Results: As shown in the Table, there were significant differences in NIHSS scores and vascular risk factors across age groups. TOAST subtype distribution was significantly different across age groups (p<0.001, with higher percentage of large-artery and cardio-embolic in older age groups and other well-defined causes in 18-49y age group. Cryptogenic strokes ("undetermined") were less common in 18-49y group (13% vs 20% vs 21%, p=0.02), possibly because PFO-associated strokes are included under the cardio-embolic category. The rates of diagnostic tests performed were significantly different, as was their diagnostic yield, e.g. toxicology screening was common (63%) in the 18-49y age group with a diagnostic yield of 11%; in the 75+ year age group it was performed in only 38% whereas the yield was not negligible (5%). Conclusion: Rates of cryptogenic stroke differ significantly across age groups. This may partly be explained by differences in the extent of diagnostic evaluations. Our results may have implications for stroke management however more research is warranted to determine the cost-effectiveness of diagnostic tests and design appropriate treatment strategies.