Atherosclerotic vulnerable plaques in carotid and intracranial arteries are significantly associated with ischemic stroke. Atherosclerosis, as a systemic disease, commonly involves multiple vascular beds simultaneously, such as carotid and intracranial arteries ^[1-2]. Most recently, 3D multicontrast MR vessel wall imaging technique has been proposed ^[3]. This technique enables comprehensive characterization of intra- and extra-cranial artery diseases due to its fast acquisition, excellent blood suppression and large longitudinal coverage ^[3]. Evaluation of co-existing atherosclerotic plaques in intra- and extra-cranial arteries and their relationships with cerebral ischemic lesions is important for stroke prevention.This study sought to investigate the characteristics of co-existing atherosclerotic plaques in intra- and extra-cranial arteries and their relationships with ischemic stroke by using 3D multicontrast MR vessel wall imaging.MR imaging: Fifty-eight patients (mean age: 58.0 ± 8.5 years, 34 males) with recent neurovascular symptoms and carotid atherosclerotic plaque were recruited. All patients underwent brain and neurovascular MR imaging at 3.0T Philips MR scanner with custom-designed 36-channel neurovascular coil ^[4]. For intra- and extra-cranial artery vessel wall imaging, a 3D multicontrast vessel wall imaging protocol was conducted to acquire 3D MERGE, 3D SNAP, and 3D T2-VISTA imaging sequences with the following parameters: 3D MERGE: FFE, TR/TE 9.2/4.3ms, flip angle 6°; 3D SNAP: FFE, TR/TE 9.9/4.8 ms, flip angle 11/5°; and 3D T2-VISTA: TSE, TR/TE 2500/278 ms, flip angle 90°. All 3D imaging sequences were acquired coronally with the same FOV of 40x160x250mm³ and isotropic spatial resolution of 0.8x0.8x0.8mm³. A clinically standard imaging protocol including T1w, T2w and DWI was used to image brain. Image review: The intra- and extra-cranial arteries were divided into the following segments: M1 segment of middle cerebral artery (MCA), C3-7 segment of internal carotid artery (ICA), C2 segment of ICA, C1 segment of ICA, bulb, and common carotid artery (CCA). Presence/absence of atherosclerotic plaque at each arterial segment was identified. The maximum wall thickness (MaxWT), length, stenosis of each plaque was measured. The presence/absence of calcification, lipid-rich necrotic core (LRNC), and intraplaque hemorrhage (IPH) was assessed. Cerebral old and acute infarcts in anterior circulation were evaluated. Statistical analysis: The prevalence of plaque and its composition at each arterial segment was calculated. Logistic regression was utilized to determine the odds ratio (OR) and corresponding 95% confidence interval (CI) of plaque features in discriminating recurrent stroke.Co-existing intra- and extra-cranial artery plaques were found in 45 patients (77.6%), of which 7 (15.6%) had first stroke and 26 (57.8%) had recurrent stroke in territory of anterior circulation. The plaque characteristics were summarized in Figure 1. The number of plaques in intra-cranial artery, extra-cranial artery and both intra- and extra-cranial arteries was 1.6±1.3, 2.0±1.1, and 3.6±1.9, respectively. For the 33 patients with co-existing intra- and extra-cranial plaques and infarcts in anterior circulation, the number of intra-cranial plaques (OR=11.26; 95% CI, 1.27-100.23; p=0.030) and the number of co-existing intra- and extra-cranial plaques (OR=2.42; 95% CI, 1.04-5.64; p=0.040) were associated with recurrent stroke. After adjusting for traditional risk factors, the recurrent stroke was still significantly correlated with thel number of co-existing intra- and extra-cranial plaques (OR=3.31; 95% CI, 1.09-10.08; p=0.035) but not with number of intra-cranial plaques (OR=16.72; 95% CI, 0.97-288.08; p=0.052). An example was presented in Figure 2. No correlation was found between recurrent stroke and MaxWT, length, and stenosis of plaques.We found that the coexisting intra- and extra-cranial plaques were prevalent in stroke patients. Previous study reported that 43% of stroke patients had co-existing lesions ^[2] which is much lower than our results (77.6%). This might be due to the use of MR vessel wall imaging techniques which enables direct visualization of the lesions in arterial wall and successful characterization of plaque burden and compositions.Since there is positive remodeling effect, particularly for early atherosclerotic lesions, measuring luminal stenosis which is widely used in previous studies will underestimate the disease. We found that the number of co-existing intra- and extra-cranial plaques was independently associated with recurrent stroke. The number of atherosclerotic plaques may represent the overall plaque burden in multiple vascular beds. The plaque number can be determined by a single 3D imaging sequence, such as MERGE or VISTA. Our findings suggest that the number of co-existing intra- and extra-cranial plaques might be an independent indicator for the risk of recurrent stroke.The coexisting intra- and extra-cranial plaques are prevalent in stroke patients. The number of co-existing plaques is independently associated with the risk of recurrent stroke.