Focal Hypoperfusion on Baseline Perfusion-Weighted MRI and the Risk of Subsequent Cerebrovascular Events in Patients With TIA.

Abstract

BACKGROUND AND OBJECTIVES While MRI is known to be crucial for TIA workup, the benefit of perfusion-weighted imaging (PWI) is underexplored. We aimed to assess the association between focal hypoperfusion on baseline PWI MRI and the long-term incidence of subsequent acute ischemic stroke (AIS) after TIA. METHODS Consecutive patients with TIA who underwent baseline PWI MRI as part of their emergency consultation between January 2015 and December 2019 were retrospectively identified. For study inclusion, both a time-based (symptom duration <24 hours) and an imaging-based (no signs of ischemia on diffusion-weighted imaging) TIA definition were applied. Long-term incidences of AIS after TIA were identified based on follow-up reports. Associations between focal hypoperfusion and subsequent AIS were assessed using Cox regression models adjusted for predefined predictors of stroke occurrence including symptomatic extracranial or intracranial stenosis. In subgroup analyses, we aimed to determine effects of focal hypoperfusion within vs outside the expected TIA territory, defined as a brain region potentially correlating with TIA symptoms. RESULTS Of 1,359 eligible patients with TIA, 1,075 with PWI MRI (79%) were included (median age 70 years, 46% female). Focal hypoperfusion was identified in 211 patients (20%); in 116 of 211 (55%), hypoperfusion occurred within the expected TIA territory. The median time from symptom onset to imaging was 233 minutes (interquartile range [IQR] 131-632) for patients with focal hypoperfusion vs 229 minutes [IQR 140-441] for patients without (p = 0.42). Focal hypoperfusion was associated with a higher incidence of AIS (adjusted hazard ratio [aHR] 2.13; 95% CI 1.19-3.80). While this was observed for focal hypoperfusion within the expected TIA territory (aHR 3.95; 95% CI 2.05-7.60), there was no such association in case of focal hypoperfusion outside the expected TIA territory (aHR 0.72; 95% CI 0.25-2.03). DISCUSSION Focal hypoperfusion on acute PWI MRI was found in 1 in 5 patients with TIA. It was associated with a higher incidence of AIS during long-term follow-up, especially when within the expected TIA territory. Further research is needed to clarify the predictive value of focal hypoperfusion in relation to the incidence of AIS after TIA and to explore potential therapeutic implications.