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Reply: REPLY: that DWI is the criterion standard in the setting of lacunar in- farcts. A recent study showed that up to 29% of patients with e thank Morelli et al for their comments regarding our nondisabling ischemic stroke have negative findings on DWI, and Warticle “CT Perfusion in Acute Lacunar Stroke: Detection the prognosis in patients with negative findings on DWI was no Capabilities Based on Infarct Location.” We acknowledge the im- better than those with positive findings on DWI. Furthermore, portant points our colleagues raised concerning lacunar infarcts DWI positive for lesions in the setting of acute stroke sometimes and have responded to those comments below. demonstrates reversal of restricted diffusion. Our study com- To begin, we agree that the size of lacunae should be defined as pared CTP imaging with DWI—not with the clinical presence or 15–20 mm. Although both 15 and 20 mm have been suggested absence of lacunar syndrome. The diagnostic capability of DWI as the uppermost diameter limit for lacunar infarcts, we chose to would, therefore, naturally be superior to that of CTP because use 20 mm to be consistent with other recent publications on the DWI was used as the criterion standard in our study. A direct topic. comparison of both CTP and DWI with the presence or absence However, we disagree with our colleagues’ conclusion that the of clinically apparent lacunae would be needed to determine the definition of lacunae should only be used for infarcts within the relative sensitivity of both modalities, which was not performed in deep perforator territory. Such restrictive use of the term “lacu- this study. This, too, is an area of potential future research. nae” ignores the variability in vascular supply throughout the brain. For example, supply to the caudate head from the artery of Heubner may arise either as a medial lenticulostriatal perforator REFERENCES or as a direct artery. Thus, the necessity that lacunar infarcts be 1. Das T, Settecase F, Boulos M, et al. Multimodal CT provides improved located in the “deep” perforator territory prevents the inclusion of performance for lacunar infarct detection. AJNR Am J Neuroradiol subcortical infarcts, which were shown in a study of 3660 partic- 2015;36:1069–75 CrossRef Medline ipants to represent 11.9% of lacunae. 2. Longstreth WT, Bernick C, Manolio TA, et al. Lacunar infarcts de- fined by magnetic resonance imaging of 3660 elderly people: the Car- Nevertheless, the distinction should be made between diovascular Health Study. Arch Neurol 1998;55:1217–25 Medline periventricular white matter (PVWM) contiguous with the ven- 3. Fazekas F, Chawluk JB, Alavi A, et al. MR signal abnormalities at 1.5 T tricle, deep white matter (DWM), and subcortical white matter in Alzheimer’s dementia and normal aging. AJR Am J Roentgenol (SCWM) immediately subjacent to the cortex. According to this 1987;149:351–56 CrossRef Medline 3 4 classification system used by Fazekas et al and Kim et al, the 4. Kim KW, MacFall JR, Payne ME. Classification of white matter le- infarcts in Figs 2 and 3 of our article would be better classified as sions on magnetic resonance imaging in elderly persons. Biol Psychi- atry 2008;64:273–80 CrossRef Medline DWM, rather than SCWM as our colleagues stated, because they 5. Makin SD, Doubal FN, Dennis MS, et al. Clinically confirmed stroke are located several millimeters deep to the unaffected overlying with negative diffusion-weighted imaging magnetic resonance 3,4 cortex. Even if our colleagues’ presumption that only “deep” imaging: longitudinal study of clinical outcomes, stroke recurrence, infarcts may be classified as lacunae is correct, it is speculative to and systematic review. Stroke 2015;46:3142–48 CrossRef Medline conclude that these infarcts must be within the PVWM rather 6. Olivot JM, Mlynash M, Thijs VN, et al. Relationships between cere- bral perfusion and reversibility of acute diffusion lesions in than the DWM. DEFUSE: insights from RADAR. Stroke 2009;40:1692–97 CrossRef Next, we agree with our colleagues that the contrast-to-noise Medline (CNR) ratio and 10-mm sections are limitations of CTP imaging; J.C. Benson both the CNR and section thickness may lead to partial volume Department of Radiology artifacts, affect the absolute infarct size on CBV, and cause smaller University of Minnesota Medical Center Minneapolis, Minnesota infarcts to be missed. However, one aim of our study was to assess S. Payabvash whether an abnormal perfusion or delay (ie, CBF and MTT) is Department of Radiology present in the setting of lacunar infarcts, which theoretically could University of California San Francisco San Francisco, California affect a larger area than a lacune (an example of this is seen in Fig B. Hoffman 2). Hence, the sensitivity of CTP may be higher than first sus- M. Oswood pected because it may be used to arouse suspicion of lacunar in- Department of Radiology Hennepin County Medical Center farcts when a severely elevated MTT or TTP region is observed. Minneapolis, Minnesota This is an area that deserves further study. A.M. McKinney Finally, it is important to address our colleagues’ presumption Department of Radiology University of Minnesota Medical Center http://dx.doi.org/10.3174/ajnr.A4991 Minneapolis, Minnesota AJNR Am J Neuroradiol 38:E13 Feb 2017 www.ajnr.org E13 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
© 2017 by American Journal of Neuroradiology
ISSN
0195-6108
eISSN
1936-959X
DOI
10.3174/ajnr.A4991
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27737861
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Abstract

REPLY: that DWI is the criterion standard in the setting of lacunar in- farcts. A recent study showed that up to 29% of patients with e thank Morelli et al for their comments regarding our nondisabling ischemic stroke have negative findings on DWI, and Warticle “CT Perfusion in Acute Lacunar Stroke: Detection the prognosis in patients with negative findings on DWI was no Capabilities Based on Infarct Location.” We acknowledge the im- better than those with positive findings on DWI. Furthermore, portant points our colleagues raised concerning lacunar infarcts DWI positive for lesions in the setting of acute stroke sometimes and have responded to those comments below. demonstrates reversal of restricted diffusion. Our study com- To begin, we agree that the size of lacunae should be defined as pared CTP imaging with DWI—not with the clinical presence or 15–20 mm. Although both 15 and 20 mm have been suggested absence of lacunar syndrome. The diagnostic capability of DWI as the uppermost diameter limit for lacunar infarcts, we chose to would, therefore, naturally be superior to that of CTP because use 20 mm to be consistent with other recent publications on the DWI was used as the criterion standard in our study. A direct topic. comparison of both CTP and DWI with the presence or absence However, we disagree with our colleagues’ conclusion that the of clinically apparent lacunae would be needed to determine the definition of lacunae should only be used for infarcts within the relative sensitivity of both modalities, which was not performed in deep perforator territory. Such restrictive use of the term “lacu- this study. This, too, is an area of potential future research. nae” ignores the variability in vascular supply throughout the brain. For example, supply to the caudate head from the artery of Heubner may arise either as a medial lenticulostriatal perforator REFERENCES or as a direct artery. Thus, the necessity that lacunar infarcts be 1. Das T, Settecase F, Boulos M, et al. Multimodal CT provides improved located in the “deep” perforator territory prevents the inclusion of performance for lacunar infarct detection. AJNR Am J Neuroradiol subcortical infarcts, which were shown in a study of 3660 partic- 2015;36:1069–75 CrossRef Medline ipants to represent 11.9% of lacunae. 2. Longstreth WT, Bernick C, Manolio TA, et al. Lacunar infarcts de- fined by magnetic resonance imaging of 3660 elderly people: the Car- Nevertheless, the distinction should be made between diovascular Health Study. Arch Neurol 1998;55:1217–25 Medline periventricular white matter (PVWM) contiguous with the ven- 3. Fazekas F, Chawluk JB, Alavi A, et al. MR signal abnormalities at 1.5 T tricle, deep white matter (DWM), and subcortical white matter in Alzheimer’s dementia and normal aging. AJR Am J Roentgenol (SCWM) immediately subjacent to the cortex. According to this 1987;149:351–56 CrossRef Medline 3 4 classification system used by Fazekas et al and Kim et al, the 4. Kim KW, MacFall JR, Payne ME. Classification of white matter le- infarcts in Figs 2 and 3 of our article would be better classified as sions on magnetic resonance imaging in elderly persons. Biol Psychi- atry 2008;64:273–80 CrossRef Medline DWM, rather than SCWM as our colleagues stated, because they 5. Makin SD, Doubal FN, Dennis MS, et al. Clinically confirmed stroke are located several millimeters deep to the unaffected overlying with negative diffusion-weighted imaging magnetic resonance 3,4 cortex. Even if our colleagues’ presumption that only “deep” imaging: longitudinal study of clinical outcomes, stroke recurrence, infarcts may be classified as lacunae is correct, it is speculative to and systematic review. Stroke 2015;46:3142–48 CrossRef Medline conclude that these infarcts must be within the PVWM rather 6. Olivot JM, Mlynash M, Thijs VN, et al. Relationships between cere- bral perfusion and reversibility of acute diffusion lesions in than the DWM. DEFUSE: insights from RADAR. Stroke 2009;40:1692–97 CrossRef Next, we agree with our colleagues that the contrast-to-noise Medline (CNR) ratio and 10-mm sections are limitations of CTP imaging; J.C. Benson both the CNR and section thickness may lead to partial volume Department of Radiology artifacts, affect the absolute infarct size on CBV, and cause smaller University of Minnesota Medical Center Minneapolis, Minnesota infarcts to be missed. However, one aim of our study was to assess S. Payabvash whether an abnormal perfusion or delay (ie, CBF and MTT) is Department of Radiology present in the setting of lacunar infarcts, which theoretically could University of California San Francisco San Francisco, California affect a larger area than a lacune (an example of this is seen in Fig B. Hoffman 2). Hence, the sensitivity of CTP may be higher than first sus- M. Oswood pected because it may be used to arouse suspicion of lacunar in- Department of Radiology Hennepin County Medical Center farcts when a severely elevated MTT or TTP region is observed. Minneapolis, Minnesota This is an area that deserves further study. A.M. McKinney Finally, it is important to address our colleagues’ presumption Department of Radiology University of Minnesota Medical Center http://dx.doi.org/10.3174/ajnr.A4991 Minneapolis, Minnesota AJNR Am J Neuroradiol 38:E13 Feb 2017 www.ajnr.org E13

Journal

American Journal of NeuroradiologyAmerican Journal of Neuroradiology

Published: Feb 1, 2017

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