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- Moo Seok Park, MD,
- Jihoon Cha, MD,
- Jong-Won Chung, MD,
- Woo-Keun Seo, MD,
- Gyeong-Moon Kim, MD, PhD and
- Oh Young Bang, MD, PhD∗ ()
- ↵∗Department of Neurology, Samsung Medical Center, Sungkyunkwan University, 81, Irwon-Ro, Gangnam-gu, Seoul 06351, Republic of Korea
Intracranial steno-occlusive disease is a common cause of stroke worldwide and is more prevalent in Asians. We hypothesized that nontraumatic intracranial artery dissection (ICAD) is a common hidden cause of large intracranial steno-occlusive disease in Asian patients with ischemic stroke and that many patients with ICAD may be misclassified as having intracranial atherosclerotic stenosis (ICAS). Thus we performed high-resolution magnetic resonance imaging (HR-MRI) in patients with acute ischemic stroke and intracranial arterial stenosis with no potential sources of proximal embolism.
We prospectively recruited consecutive patients with acute symptomatic infarcts caused by intracranial occlusive disease who were admitted to a university medical center between January 2011 and October 2016. We defined potential participants as having the following: 1) acute cerebral infarct; 2) imaging such as time-of-flight (TOF) magnetic resonance angiography (MRA) showing significant (≥50%) stenosis of the intracranial vessels; 3) absence of extracranial stenosis (≥50%) or occlusion of arteries supplying the area of ischemia; 4) no potential sources of cardioembolism; and 5) no history of trauma within 1 month of stroke onset. Local institutional review boards approved this study.
HR-MRI was performed in these patients, especially when vascular studies gave controversial results in the diagnosis of ICAS, ICAD, or other causes of intracranial steno-occlusive disease. Typical luminal changes include densely calcified and multiple tandem stenosis for ICAS, pathognomonic findings of dissection (e.g., intimal flap, double lumen, and aneurysmal formation), and aberrant basal collateral vessels for moyamoya disease (MMD). HR-MRI was performed on culprit lesions located in the distal portion of the internal carotid artery with a 3-T system (Achieva, Philips Medical Systems, Best, the Netherlands). Details of HR-MRI parameters are described elsewhere (1). Two neurologists read the HR-MRI images. HR-MRI findings of the presence of an intimal flap or a double lumen, an intravascular hematoma, or aneurysmal formation were used for ICAD, and the presence of plaque was used for ICAS (2).
Clinical, laboratory, and HR-MRI findings were compared between the ICAS and ICAD groups: group A (patients with frank ICAD, documented by initial TOF-MRA), group B (patients with hidden ICAD, documented only by HR-MRI and no typical luminal changes of ICAD), and group C (patients with HR-MRI–confirmed ICAS). Student t tests, Fisher exact tests, Mann-Whitney U tests, and Kruskal-Wallis tests were used to compare binary and continuous variables among the groups.
Among 937 patients with acute ischemic stroke who had evidence of intracranial stenosis on TOF-MRA, 627 patients were finally included in this study. Characteristic luminal changes of ICAD were observed in 69 patients (group A), and HR-MRI was performed in the remaining 558 patients. On the basis of the HR-MRI features, 123 (22.0%) patients were additionally classified as having ICAD (group B) and 252 (45.2%) were classified as having ICAS. ICAD was prevalent in this study population (the ratio of ICAD to ICAS was 1:2.86), and almost two-thirds (123 of 192 patients) of ICAD did not show typical luminal changes of ICAD. Interrater agreement was excellent (κ = 0.886). Patients’ characteristics were different among the groups (Figure 1).
Clinical and laboratory findings were not different between patients in group A and those in group B. Women, older patients, hypertension, and diabetes were more frequent in group C than in groups A or B.
Our study showed that ICAD is a prevalent hidden cause of intracranial steno-occlusive disease in an East Asian population. Luminal evaluation is the traditional method for diagnosis of ICAD, but the pathognomonic luminal findings of arterial dissection were seldom observed in small arteries such as intracranial arteries. Almost two-thirds of our patients with ICAD were misclassified as having ICAS on the basis of current luminal imaging techniques. HR-MRI should be considered in the differential diagnosis between ICAD and ICAS, especially in young patients with no luminal vascular risk factors.
This was a single-center study, and further studies from other study population are needed to confirm our results. However, this was a large series of prospectively collected HR-confirmed ICAD cases. Our results are in line with the recent HR-MRI studies of young patients with unilateral middle cerebral artery stenosis and minimal risk factors (3).
When considering the differential therapeutic and prognostic approaches between ICAD and ICAS, HR-MRI is a useful and noninvasive diagnostic tool in the East Asian population. Further studies are warranted to determine the need for time-consuming HR-MRI that may be helpful in treatment of patients with intracranial stenosis (e.g., avoidance of lifelong use of high-intensity statin treatment or stenting in ICAD with a relatively benign course).
Please note: This research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HC15C1056). The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation
- Ryoo S.,
- Lee M.J.,
- Cha J.,
- Jeon P.,
- Bang O.Y.
- Ahn S.H.,
- Lee J.,
- Kim Y.J.,
- et al.