Neurology -- Correspondence for Kubo et al., 66 (10) 1539-1544

Correspondence published:

Decreasing incidence of lacunar vs other types of cerebral infarction in a Japanese population: Antonino Tuttolomondo, Antonio Pinto, Domenico Di Raimondo, Paola Fernandez, Giuseppe Licata (18 July 2006)

Reply from the Authors: Michiaki Kubo, Toshiharu Ninomiya, Yumihiro Tanizaki, and Yutaka Kiyohara (18 July 2006)

Decreasing incidence of lacunar vs other types of cerebral infarction in a Japanese population 18 July 2006

Antonino Tuttolomondo,
Department of Internal Medicine , University of Palermo
P.zza delle Cliniche n.2 , 90127 Palermo, Italy,
Antonio Pinto, Domenico Di Raimondo, Paola Fernandez, Giuseppe Licata
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Re: Decreasing incidence of lacunar vs other types of cerebral infarction in a Japanese population

pinto{at}neomedia.it Antonino Tuttolomondo, et al.

We read the article by Kubo et al [1] with interest and have questions pertinent to the study. How many patients died and had an autopsy in every cohort? How many patients classified as lacunar had on autopsy a suggestive brain lesion? Is it possible that an autoptic finding of lacunar stroke could have been a silent stroke instead of a lacunar stroke effectively responsible for patients' symptomatology? According to the TOAST classification criteria of lacunar strokes with absence of lesion on brain imaging, how did Kubo et al classify a patient with a previous lacunar syndrome and negative autoptical evidence? Furthermore, was white matter hyperintensity on brain imaging or autopsy considered in the process of stroke subtype diagnosis? What is the agreement between clinical and autoptic definition of stroke subtypes in every cohort? How many patients had �previously known diabetes�, how many �new diagnosed diabetes� and how many �IGT or IFT�?
In this study, lacunar subtype was the most prevalent subtype which contradicts other reports that included a Western population. [2,3] The authors explain this finding with possible race and lifestyle-related factors but we believe the epidemiologic weight of lacunar stroke in Western studies could be understimated. We appreciate that Kubo et al used autopsy findings to classify the ischemic stroke subtype which clarifies the subtypes definition. In our opinion, the higher prevalence of lacunar subtype in this study could not only be related to geographic or racial peculiarity of the Japanese population but also simply due to the higher accuracy of diagnostic subtype definition by imaging and autopsy.
In an observational study conducted in Palermo, we [4] observed a higher prevalence, compared to other studies, of lacunar strokes between 303 patients with ischemic stroke even if this finding could be probably related to the high prevalence of diabetics in our population. Megherbi [5] showed a higher prevalence of lacunar strokes in diabetics. Kubo et al reported in each cohort a percentage of hypertension comparable to other studies but the prevalence of glucose metabolism disorders generically grouped by the authors by the term � glucose intolerance� appears lower in comparison with previous reports. [2,3]
Finally, could lacunar stroke represent an underestimated �Western� subtype of stroke?
References
1. Kubo M, Kiyohara Y, Ninomiya T, et al. Decreasing incidence of lacunar vs other types of cerebral infarction in a Japanese population. Neurology 2006; 66: 1539-1544.
2. Petty GW, Brown RD Jr, Whisnant JP, Sicks JD, O�Fallon WM, Wiebers DO. Ischemic stroke subtypes: a population-based study of incidence and risk factors. Stroke 1999; 30: 2513-2516.
3. Woo D, Gebel J, Miller R, et al. Incidence rates of first-ever ischemic stroke subtypes among blacks: a population study. Stroke 1999; 30: 2517-2522
4. Pinto A, Tuttolomondo A, Di Raimondo D, Fernandez P, Licata G. Cerebrovascular risk factors and clinical classification of strokes. Semin Vasc Med. 2004 Aug;4:287-303.
5. Megherbi SE, Milan C, Minier D, et al. European BIOMED Study of Stroke Care Group Association between diabetes and stroke subtype on survival and functional outcome 3 months after stroke: data from the European BIOMED Stroke Project. Stroke. 2003 Mar;34:688-94.
Disclosure: The authors report no conflicts of interest.

Reply from the Authors 18 July 2006

Michiaki Kubo,
Department of Environmental Medicine, Graduate School of Medical Sciences, Kyushu University
3-1-1, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan,
Toshiharu Ninomiya, Yumihiro Tanizaki, and Yutaka Kiyohara
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Re: Reply from the Authors

kubomich{at}intmed2.med.kyushu-u.ac.jp Michiaki Kubo, et al.

We appreciate the interest of Dr Tuttolomondo et al in our recent work analyzing secular trend in the incidence of ischemic stroke subtypes using three study cohorts.[1] They ask some questions to which we have the following responses.
In our study, morphological examination by autopsy was performed on 109 subjects (89.3% of subjects with ischemic stroke) in the first cohort, 87 subjects (70.2%) in the second cohort, and 51 subjects (37.2%) in the third cohort. The remaining 32 subjects with ischemic stroke (25.8%) in the second cohort and all 137 subjects with ischemic stroke in the third cohort underwent examination with brain imaging.
Of 212 subjects who developed lacunar infarction in three cohorts, 122 (57.5%) were morphologically examined by autopsy and the remaining 79 (37.3%) by brain imaging. Since we considered morphological findings significant and the existence of pathological lesions corresponding to neurological findings essential for the diagnosis of ischemic stroke, all subjects with lacunar infarction under autopsy examination had significant pathological findings.[6] Thus silent strokes did not count as lacunar infarctions.
Moreover, we did not use white matter hyperintensity on brain imaging or leukoaraiosis on autopsy as a diagnostic tool of lacunar infarction. We classified most cases of ischemic stroke into subtypes retrospectively by searching preferentially pathological lesions corresponding to neurological findings, and thus we did not estimate the concordance rate between clinical diagnosis and autopsy findings.
A 75g oral glucose tolerance test was performed in almost all study subjects of the third cohort but was not in those of the first and second cohort.[7] Among the 137 subjects with ischemic stroke in the third cohort, 22 had previously known diabetes, 9 had newly diagnosed diabetes, and 21 had impaired glucose tolerance or impaired fasting glucose.
In our Japanese population, lacunar infarction was the most common subtype of ischemic stroke, contrary to the previous reports of Western populations.[2,3] This discrepancy cannot be explained by the differences in the frequencies of major risk factors, such as hypertension and diabetes, between the populations. The differences in race and lifestyle- related factors including diet might contribute to this discrepancy.
Further study and consideration are needed to clarify the issue raised by Dr Tuttolomondo et al regarding the underestimation of epidemiological weight of lacunar infarction in Western studies.
References
6. Tanizaki Y, Kiyohara Y, Kato I, et al. Incidence and risk factors for subtypes of cerebral infarction in a general population: the Hisayama study. Stroke 2000; 31:2626-2622.
7. Kubo M, Kiyohara Y, Kato I, et al. Trends in the incidence, mortality, and survival rate of cardiovascular disease in a Japanese community: the Hisayama study. Stroke 2003; 34:2349-2354.
Disclosure: The authors report no conflicts of interest.