OBJECT The objective of this study was to generate data on the local prevalence of unruptured intracranial aneurysms (UIAs) in asymptomatic Hong Kong Chinese individuals. First-degree relatives of patients with aneurysmal subarachnoid hemorrhage (aSAH) were recruited as surrogates of the general population and to explore the potential role of screening in this locality. METHODS The authors identified first-degree relatives of consecutive patients with subarachnoid hemorrhage from a ruptured aneurysm who were admitted to a university hospital in Hong Kong from June 2008 to December 2010. Magnetic resonance angiography (MRA) was the imaging modality used to screen the cerebral vasculature of these asymptomatic individuals. If MRA showed abnormal findings, CT angiography was performed to confirm the MRA findings. RESULTS In total, 7 UIAs were identified from the 305 MR angiograms obtained. The prevalence of UIAs in first-degree relatives of patients with aSAH in the Hong Kong Chinese population was 2.30% (95% CI1.02%-4.76%). This percentage was lower than the prevalence rate of 3.2% from a meta-analysis of the literature. The sizes of the UIAs detected ranged from 1.4 mm to 7.5 mm; 85.7% of the UIAs detected in this study were < 5 mm, in contrast to 66% noted in the literature. One of the UIAs identified underwent endovascular stent placement with a flow diverter. None of the UIAs identified ruptured or became symptomatic during a median follow-up period of 3.5 years. CONCLUSIONS The prevalence of UIAs in first-degree relatives of patients with aSAH in the Hong Kong Chinese population was lower than that in Caucasians. At the same time, most of the UIAs detected in this study were small (85.7% were < 5 mm, vs 66% in a meta-analysis). With a similar incidence of aSAH in Hong Kong (7.5 per 100,000 person-years) as compared with data cited in the literature, the hypothesis that UIA rupture risk size threshold is different in Chinese patients should be further investigated.
Keywords: ACoA = anterior communicating artery; CTA = CT angiography; Chinese; Hong Kong; ICA = internal carotid artery; MRA = MR angiography; SAH = subarachnoid hemorrhage; UIA= unruptured intracranial aneurysm; VA = vertebral artery; aSAH = aneurysmal SAH; first-degree relative; prevalence; screening; subarachnoid hemorrhage; unruptured intracranial aneurysm; vascular disorders.