Clinical and radiological correlates of reduced cerebral blood flow measured using magnetic resonance imaging

Abstract

Background: Methods for determining cerebral blood flow (CBF) using bolus-tracking magnetic resonance imaging (MRI) have recently become available. Reduced apparent diffusion coefficient (ADC) values of brain tissue are associated with reductions in regional CBF in animal stroke models. Objectives: To determine the clinical and radiological features of patients with severe reductions in CBF on MRI and to analyze the relationship between reduced CBF and ADCs in acute ischemic stroke. Design: Case series. Setting: Referral center. Methods: We studied 17 patients with nonlacunar acute ischemic stroke in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) were performed within 7 hours of symptom onset. A PWI-DWI mismatch of more than 20% was required. We compared patients with ischemic lesions that had CBF of less than 50% relative to the contralateral hemisphere with patients with lesions that had relative CBF greater than 50%. Characteristics analyzed included age, time to MRI, baseline National Institutes of Health Stroke Scale score, mean ADC, DWI and PWI lesion volumes, and 1-month Barthel Index score. Results: Patients with low CBF (n = 5) had lower ADC values (median, 430 x 10-6 mm2/s vs 506 x 10-6 mm2/s; P = .04), larger DWI volumes (median, 41.8 cm3 vs 14.5 cm3; P = .001) and larger PWI lesions as defined by the mean transit time volume (median, 194.6 cm3 vs 69.3 cm3; P = .01), and more severe baseline National Institutes of Health Stroke Scale scores (median, 15 vs 9; P = .02). Conclusion: Ischemic lesions with severe CBF reductions, measured using bolus-tracking MRI, are associated with lower mean ADCs, larger DWI and PWI volumes, and higher National Institutes of Health Stroke Scale scores.