Ivy sign, misery perfusion, and asymptomatic moyamoya disease: FLAIR imaging and 15O-gas positron emission tomography

The prevalence of ivy sign on fluid-attenuated inversion recovery (FLAIR) imaging in patients with asymptomatic moyamoya disease is unclear. The aim of this study was to clarify the incidence of ivy sign in these patients, as well as the correlation between MRI and O-15 gas PET findings. A retrospective analysis including 16 consecutive patients with asymptomatic moyamoya disease enrolled between 2001 and 2010 in a single center. FLAIR imaging at the initial visit was categorized as ivy sign present, negative, or equivocal. Hemodynamic and metabolic parameters were quantified in 11 of 16 patients by O-15-gas positron emission tomography, and the relationship between ivy sign and O-15-gas PET parameters was analyzed. Cerebrovascular events within the follow-up period (54 +/- 28 months) were also examined. Five of 16 asymptomatic moyamoya patients (31.3 %) had positive ivy sign (6/30 hemispheres, 20 %). In O-15-gas PET examinations, 18 % of 22 hemispheres had elevated oxygen extraction fraction values that were significantly associated with positive ivy sign. Of these 16 asymptomatic moyamoya patients, six patients (37.5 %) underwent combined surgical revascularization. In this series, no patients experienced ischemic stroke, but one had intraventricular bleeding 1 year after surgery. Ivy sign on FLAIR imaging is still not rare in patients with moyamoya disease, even when asymptomatic. Although optimal management is still under debate, ivy sign may be an indicator of misery perfusion, and patients with asymptomatic moyamoya disease and ivy sign on FLAIR imaging will benefit from more careful follow-up.