Abstract 158: Magnetic Resonance Angiography Signal Intensity as a Marker of Hemodynamic Impairment in Intracranial Arterial Stenosis

Abstract

Background and Purpose:— Intracranial arterial stenosis (ICAS) is the predominant cause of ischemic stroke or transient ischemic attack (TIA) in Asia. Change of signal intensities (SI) across an ICAS on magnetic resonance angiography (MRA) may reflect hemodynamic severity of such lesions. Methods:— In-patients with a symptomatic single ICAS of anterior circulation on 3D time-of-flight MRA were recruited. Baseline and 1-year follow-up data were collected. Signal intensity ratio (SIR) was calculated to represent change of SIs across an ICAS on maximum intensity projections: SIR=(mean post-stenotic SI - mean background SI)/(mean pre-stenotic SI - mean background SI). Acute infarct volume was measured on diffusion-weighted images (DWI). Relationships of SIR and baseline characteristics as well as 1-year outcomes were evaluated. Results:— Thirty-six subjects (86.1% males, mean age 55.0 years) were recruited. Overall, mean SIR was 0.84±0.23. Mean SIR of the 23 (63.9%) anatomically severe stenoses was insignificantly lower than the 13 (36.1%) moderate stenoses (0.80±0.23 versus 0.92±0.21, p=0.126). The median baseline infarct volume for the 28 (77.8%) subjects with lesions on DWI was 2.40 cm 3 (IQR 0.80 to 5.78). SIR and acute infarct volume were significantly, linearly and negatively correlated, Spearman correlation coefficient being -0.471 (p=0.011). Two patients (5.6%) had recurrent ischemic strokes at 1-year follow-up. SIR values or acute infarct volumes were unrelated to 1-year outcomes in this initial study. Conclusion:— Change of signal intensity across ICAS on MRA may reflect hemodynamic and functional severity of the lesion. Future studies are warranted to further verify the relationship between this index and prognosis of stroke patients.