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Reply: REPLY: may be more sensitive for reflecting hemodynamic changes. Physically, the CBF value will decrease when the cerebral vessels e appreciate the comments by Drs Mori and Mugikura reach the maximum of vasodilatory ability. Wand thank the editor for the opportunity to reply to those Another comment was about the correlation between the ivy comments. sign score on CEMR and CBF in the late Suzuki stage. Drs Mori As suggested by Drs Mori and Mugikura, our results may and Mugikura mentioned that posterior circulation involvement “revealed different underlying pathophysiologies” between the is often seen in this phase. In our study, we used posterior cere- two imaging modalities. Until today, most studies support the hy- bral artery involvement as a covariant to address the impact of pothesis that FLAIR vascular hyperintensity (FVH) represents this confounding factor. We completely agree that the ivy sign on slow or turbulent flow through the engorged leptomeningeal col- CEMR may be attributed to the maximally dilated pial vascula- laterals (LMCs). As to contrast-enhanced MR imaging (CEMR), ture, which includes both arterioles and venules. Although we a previous study suggested that the pial vascular enhancement in assume that the imbalance between LMCs and abnormal ICA Moyamoya disease could be attributed to a decrease of flow ve- and Moyamoya vessels may be one possible explanation, the locity–related signal losses and spin-dephasing effects, which con- underlying mechanism of the negative relationship between the sequently induce high intensity of the vessel from the mixture of ivy sign score on CEMR and CBF in the late Suzuki stage is still blood and contrast medium. The underlying pathophysiology of to be determined. Future studies with larger sample sizes, sensi- the ivy sign on CEMR and FLAIR still needs future validation to tive hemodynamic indicators and advanced imaging processing explore the association of visible imaging findings and physical approach are needed to confirm the current results. mechanisms. The main objective of our study was to develop a quantitative method on both CEMR and FLAIR and to compare the ability of REFERENCES these two imaging modalities in reference to DSA. As mentioned 1. Jiang L, Chen YC, Zhang H, et al. FLAIR vascular hyperintensity in acute stroke is associated with collateralization and functional out- by Drs Mori and Mugikura in the letter, they found that the distri- come. Eur Radiol 2019;29:4879–88 CrossRef Medline bution of FVH was more frequently seen in the anterior MCA 2. Komiyama M, Nakajima H, Nishikawa M, et al. Leptomeningeal con- region. Furthermore, they found that LMCs in the anterior and trast enhancement in Moyamoya: its potential role in postoperat- posterior regions could also change along with the Suzuki stages in ive assessment of circulation through the bypass. Neuroradiology Moyamoya disease. ASPECTS is a widely accepted approach for 2001;43:17–23 CrossRef Medline brainregionsegmentationin cerebrovascular diseases. In this 3. Mugikura S, Fujimura M, Takahashi S. Cortical microvascularization study, we used this approach and designed a total ivy sign score. and leptomeningeal collaterals in Moyamoya disease. Eur Neurol 2015;73:351–52 CrossRef Medline As a result, no statistical comparison concerning the distribution 4. Mori N, Mugikura S, Higano S, et al. The leptomeningeal “ivy sign” of the ivy sign was performed. Nevertheless, in the process of scor- on fluid-attenuated inversion recovery MR imaging in Moyamoya ing, no obvious visible difference in the distribution of the ivy sign disease: a sign of decreased cerebral vascular reserve? AJNR Am J between CEMRand FLAIRwas found. Neuroradiol 2009;30:930–05 CrossRef Medline To our knowledge, the relationship between FVH and hemody- 5. Noguchi T, Kawashima M, Nishihara M, et al. Arterial spin-labeling namic indicators, cerebrovascular reserve (CVR) and CBF for MR imaging in Moyamoya disease compared with clinical assess- 4,5 example, showed different results in previous literature. One ments and other MR imaging findings. Eur J Radiol 2013;82:e840–47 possible explanation is the result of our study. Because the presence CrossRef Medline of FVH seems to be associated with the clinical phase of the ische- mic lesion in Moyamoya disease, patients with different clinical L.X. Wang Department of Radiology phases enrolled in the previous studies may affect the consistency. First Medical Center, Chinese People’s Liberation Army General Hospital Another possible reason is the different hemodynamic indicators Beijing, China used. Compared with CBF, which was used in our study, CVR Medical School of Chinese People’s Liberation Army Beijing, China L. Ma X. Lou Department of Radiology http://dx.doi.org/10.3174/ajnr.A7233 First Medical Center, Chinese People’s Liberation Army General Hospital Beijing, China E70 Letters Sep 2021 www.ajnr.org http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png American Journal of Neuroradiology American Journal of Neuroradiology

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Publisher
American Journal of Neuroradiology
Copyright
© 2021 by American Journal of Neuroradiology
ISSN
0195-6108
eISSN
1936-959X
DOI
10.3174/ajnr.A7233
Publisher site
See Article on Publisher Site

Abstract

REPLY: may be more sensitive for reflecting hemodynamic changes. Physically, the CBF value will decrease when the cerebral vessels e appreciate the comments by Drs Mori and Mugikura reach the maximum of vasodilatory ability. Wand thank the editor for the opportunity to reply to those Another comment was about the correlation between the ivy comments. sign score on CEMR and CBF in the late Suzuki stage. Drs Mori As suggested by Drs Mori and Mugikura, our results may and Mugikura mentioned that posterior circulation involvement “revealed different underlying pathophysiologies” between the is often seen in this phase. In our study, we used posterior cere- two imaging modalities. Until today, most studies support the hy- bral artery involvement as a covariant to address the impact of pothesis that FLAIR vascular hyperintensity (FVH) represents this confounding factor. We completely agree that the ivy sign on slow or turbulent flow through the engorged leptomeningeal col- CEMR may be attributed to the maximally dilated pial vascula- laterals (LMCs). As to contrast-enhanced MR imaging (CEMR), ture, which includes both arterioles and venules. Although we a previous study suggested that the pial vascular enhancement in assume that the imbalance between LMCs and abnormal ICA Moyamoya disease could be attributed to a decrease of flow ve- and Moyamoya vessels may be one possible explanation, the locity–related signal losses and spin-dephasing effects, which con- underlying mechanism of the negative relationship between the sequently induce high intensity of the vessel from the mixture of ivy sign score on CEMR and CBF in the late Suzuki stage is still blood and contrast medium. The underlying pathophysiology of to be determined. Future studies with larger sample sizes, sensi- the ivy sign on CEMR and FLAIR still needs future validation to tive hemodynamic indicators and advanced imaging processing explore the association of visible imaging findings and physical approach are needed to confirm the current results. mechanisms. The main objective of our study was to develop a quantitative method on both CEMR and FLAIR and to compare the ability of REFERENCES these two imaging modalities in reference to DSA. As mentioned 1. Jiang L, Chen YC, Zhang H, et al. FLAIR vascular hyperintensity in acute stroke is associated with collateralization and functional out- by Drs Mori and Mugikura in the letter, they found that the distri- come. Eur Radiol 2019;29:4879–88 CrossRef Medline bution of FVH was more frequently seen in the anterior MCA 2. Komiyama M, Nakajima H, Nishikawa M, et al. Leptomeningeal con- region. Furthermore, they found that LMCs in the anterior and trast enhancement in Moyamoya: its potential role in postoperat- posterior regions could also change along with the Suzuki stages in ive assessment of circulation through the bypass. Neuroradiology Moyamoya disease. ASPECTS is a widely accepted approach for 2001;43:17–23 CrossRef Medline brainregionsegmentationin cerebrovascular diseases. In this 3. Mugikura S, Fujimura M, Takahashi S. Cortical microvascularization study, we used this approach and designed a total ivy sign score. and leptomeningeal collaterals in Moyamoya disease. Eur Neurol 2015;73:351–52 CrossRef Medline As a result, no statistical comparison concerning the distribution 4. Mori N, Mugikura S, Higano S, et al. The leptomeningeal “ivy sign” of the ivy sign was performed. Nevertheless, in the process of scor- on fluid-attenuated inversion recovery MR imaging in Moyamoya ing, no obvious visible difference in the distribution of the ivy sign disease: a sign of decreased cerebral vascular reserve? AJNR Am J between CEMRand FLAIRwas found. Neuroradiol 2009;30:930–05 CrossRef Medline To our knowledge, the relationship between FVH and hemody- 5. Noguchi T, Kawashima M, Nishihara M, et al. Arterial spin-labeling namic indicators, cerebrovascular reserve (CVR) and CBF for MR imaging in Moyamoya disease compared with clinical assess- 4,5 example, showed different results in previous literature. One ments and other MR imaging findings. Eur J Radiol 2013;82:e840–47 possible explanation is the result of our study. Because the presence CrossRef Medline of FVH seems to be associated with the clinical phase of the ische- mic lesion in Moyamoya disease, patients with different clinical L.X. Wang Department of Radiology phases enrolled in the previous studies may affect the consistency. First Medical Center, Chinese People’s Liberation Army General Hospital Another possible reason is the different hemodynamic indicators Beijing, China used. Compared with CBF, which was used in our study, CVR Medical School of Chinese People’s Liberation Army Beijing, China L. Ma X. Lou Department of Radiology http://dx.doi.org/10.3174/ajnr.A7233 First Medical Center, Chinese People’s Liberation Army General Hospital Beijing, China E70 Letters Sep 2021 www.ajnr.org

Journal

American Journal of NeuroradiologyAmerican Journal of Neuroradiology

Published: Sep 1, 2021

References