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REPLY: tion could introduce sampling error. Nonetheless, these data highlight the importance of basilar artery IPH even in low-grade e thank Drs Yuan and Sun for their interest in our article stenosis as potentially leading to stroke. High-risk plaque in in- Wand their group’s recent work on intraplaque hemorrhage tracranial arteries with 50% stenosis has been recognized as a (IPH) in carotid plaque. While IPH is validated as a high-risk potential cause of cryptogenic stroke, and identifying these high- plaque feature in extracranial carotid artery plaque due to facile risk features, including IPH, may improve the management of histologic validation from endarterectomy specimens, our cur- these patients. Nonetheless, we agree with Drs Yuan and Sun that rent understanding of the role of IPH in intracranial atheroscle- both IPH and plaque enhancement should be studied further in a rotic plaque vulnerability assessment is limited. The characteriza- prospective, longitudinal study to better understand potential im- tion of intracranial plaque features by in vivo imaging remains aging-related independent risk factors that may predict stroke. challenging due to the small plaque size and impracticality of histologic validation. The definition of T1-weighted hyperintense signal suggestive of IPH as 150% signal relative to the nearby REFERENCES medial pterygoid muscles on precontrast T1-weighted imaging 1. Zhu C, Tian X, Degnan AJ, et al. Clinical significance of intraplaque used in our study was adopted from previous carotid studies and hemorrhage in low- and high-grade basilar artery stenosis on high- resolution MRI. AJNR Am J Neuroradiol 2018;39:1286–92 CrossRef supported by initial studies of IPH within the middle cerebral Medline artery. 2. Wang X, Sun J, Zhao X, et al; CARE-II study investigators. Ipsilateral Intracranial IPH is increasingly recognized as a harbinger of plaques display higher T1 signals than contralateral plaques in re- elevated stroke risk, and our study adds to the literature concern- cently symptomatic patients with bilateral carotid intraplaque hem- ing basilar artery plaque in showing an association with stroke risk orrhage. Atherosclerosis 2017;257:78–85 CrossRef Medline 3. Saam T, Hetterich H, Hoffmann V, et al. Meta-analysis and systematic independent of the degree of stenosis. We appreciate Drs Yuan review of the predictive value of carotid plaque hemorrhage on cere- and Sun’s suggestions on the discussion of imaging sequences for brovascular events by magnetic resonance imaging. J Am Coll Cardiol improving the accuracy of intracranial IPH detection. The use of 2013;62:1081–91 CrossRef Medline different TR/TE parameters or inversion pulses can alter image 4. Turan TN, Bonilha L, Morgan PS, et al. Intraplaque hemorrhage in contrast, which may partially explain the heterogeneity of prior symptomatic intracranial atherosclerotic disease. J Neuroimaging study results. Histologic validation is preferred to standardize im- 2011;21:e159–61 CrossRef Medline 5. Yu JH, Kwak HS, Chung GH, et al. Association of intraplaque hem- aging approaches; however, it has practical challenges in intracra- orrhage and acute infarction in patients with basilar artery plaque. nial atherosclerotic plaque, which cannot be obtained in vivo. An Stroke 2015;46:2768–72 CrossRef Medline alternative practical approach to standardize sequences for clini- 6. Zhu C, Haraldsson H, Tian B, et al. High resolution imaging of the cal detection of IPH could be to use phantoms with different T1 intracranial vessel wall at 3 and 7 T using 3D fast spin echo MRI. values; this method needs to be explored further. In addition, MAGMA 2016;29:559–70 CrossRef Medline 7. Cho HJ, Kim KH, Kim EJ, et al. Clinical implications of basilar artery recent studies have increasingly used 3D high-resolution fast plaques in the pontine infarction with normal basilar angiogram: a spin-echo sequences (sampling perfection with application-opti- high-resolution magnetic resonance imaging study. J Stroke Cerebro- mized contrasts by using different flip angle evolution [SPACE] vasc Dis 2018 Sep 12. [Epub ahead of print] CrossRef Medline sequence, Siemens, Erlangen, Germany; CUBE, GE Healthcare, X C. Zhu Milwaukee, Wisconsin; or volume isotropic turbo spin-echo ac- Department of Radiology and Biomedical Imaging quisition [VISTA], Philips Healthcare, Best, the Netherlands) for University of California, San Francisco San Francisco, California intracranial plaque imaging. IPH detection should be used with X X. Tian caution because the long echo-train (30) induces considerable Department of Radiology T2-weighting, which alters contrast from traditional 2D T1- Changhai Hospital Shanghai, China weighted fast spin-echo or gradient-echo sequences. X A.J. Degnan In our study, the degree of stenosis was not associated with Department of Radiology stroke symptoms, and the prevalence of IPH was comparable in Children’s Hospital of Philadelphia low- and high-grade stenoses. This finding may reflect IPH as an Philadelphia, Pennsylvania X J. Lu independent risk factor for stroke symptoms in basilar artery X Q. Liu plaque, though the limited sample size in a single-center popula- Department of Radiology Changhai Hospital http://dx.doi.org/10.3174/ajnr.A5895 Shanghai, China E2 Letters Jan 2019 www.ajnr.org
American Journal of Neuroradiology – American Journal of Neuroradiology
Published: Jan 1, 2019
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