小出血比之前所认为的更常出现


  April 1, 2008 —最近一项来自的鹿特丹研究结果显示,60岁以上者的脑部小出血比之前所认知的更常见。
  
  研究发现,健康族群中,60至69岁者整体的脑部小出血比率为17.8%、80岁以上者为38.3%。
  
  主要研究者、荷兰鹿特丹Erasmus MC大学医学中心的Monique Breteler博士在一篇来自美国神经医学会的声明中表示,我们发现,和其它族群基础的研究相比,年长者的脑部小出血的整体发生率达3至4倍。
  
  她指出,这些发现相当重要,因为脑部小出血可能代表脑血管病变,也可能增加脑血管问题的风险。
  
  研究登载于4月1日的神经学(Neurology)期刊。
  
  【适当的MRI】
  鹿特丹研究始于1990年,是一项前溯、族群基础的研究,目标在评估年长者的疾病和厘清他们的决定因素。
  
  根据该报告,有关一般族群小出血的实际病理信息很少,它们通常伴随颅内出血(ICH),也认为小出血的病理依照不同脑部位而有所差异,脑血管淀粉样病变(CAA)引起的脑叶小出血比较深,而高血压和动脉粥样硬化会引起天幕下小出血。
  
  为了研究60岁以上者之小出血的风险因素发生率,研究者在1,062名健康个案进行脑部核磁共振(MRI),据指出,MRI是侦测脑部小出血的最适当工具。
  
  此外,研究者也评估APOE 基因型、心血管风险因素之间的关系,以及小血管疾病标记与发生小出血的情形与位置的关系。
  
  【风险因素决定位置】
  研究者推测,其研究显示出较高之小出血发生率的可能原因之一,可能是因为鹿特丹研究的研究对象年纪实际上比之前的研究大,而且目前的客制化影像技术在侦测脑部小出血上有更高的分辨率。
  
  除了较高的小出血发生率,该研究也显示APOE ε4对偶基因和出现脑叶小出血有关。
  
  作者写道,一如阿兹海默氏症, APOE ε4 对偶基因已知是脑叶ICH和CAA的风险因素,虽然实际的分子机转还不清楚, 但APOE ε4 基因会因为增加血管中β-淀粉样肽的沉积而导致出血。
  
  不过,APOE ε4 基因型与深部或者天幕下小出血无关;相对的,他们发现高收缩压和抽菸与此区域的病灶有关。
  
  作者写道,对之前的小型临床研究来说,我们的研究发现脑部小出血高发生率,以及不同风险因素造成不同区域小出血,都相当重要,小出血可能代表中风和缺血性中风造成的出血发生风险增加。
  
  该研究由Erasmus MC大学医学中心以及鹿特丹Erasmus大学、荷兰科学研究组织、荷兰健康研究与发展组织等赞助。

Microbleeds More Common Than P

By Caroline Cassels
Medscape Medical News

April 1, 2008 — The most recent results from the Rotterdam Study show cerebral microbleeds are more common in individuals over age 60 years than previously thought.

The study found the overall prevalence of cerebral microbleeds in healthy elderly subjects was 17.8% in individuals aged 60 to 69 years and 38.3% in those over age 80 years.

"We found a 3- to 4-fold higher overall prevalence of cerebral microbleeds compared with other population-based studies," principal investigator Monique Breteler, MD, PhD, from Erasmus MC University Medical Center, in Rotterdam, the Netherlands, said in a statement from the American Academy of Neurology.

"These findings are of major importance, since cerebral microbleeds likely reflect cerebrovascular pathology and may be associated with an increased risk of cerebrovascular problems," she added.

The study is published in the April 1 issue of Neurology.

Optimized MRI

Established in 1990, the Rotterdam Study is a prospective, population-based study aimed at assessing diseases in the elderly and clarifying their determinants.

According to the paper, little is known about the exact etiology of microbleeds in the general population. They often accompany intracerebral hemorrhage (ICH). It has also been suggested that the etiology of microbleeds differs according to location in the brain, with lobar microbleeds caused by cerebral amyloid angiopathy (CAA) and deep, or infratentorial, microbleeds resulting from hypertension and atherosclerosis.

To investigate the prevalence of and risk factors for microbleeds in the general population aged 60 years and older, the investigators performed brain magnetic resonance imaging (MRI) in 1062 healthy subjects. Of note, the MRI sequence was optimized for the detection of cerebral microbleeds.

In addition, investigators assessed the relationship of APOE genotype, cardiovascular risk factors, and markers of small-vessel disease to the presence and location of microbleeds.

Risk Factors Determine Location

The investigators speculate that 1 possible explanation for the higher prevalence of microbleeds in their study vs previous research may be due to the fact that Rotterdam Study population is older and their "custom-made" imaging technique has a higher sensitivity in detecting cerebral microbleeds.

In addition to a high prevalence of microbleeds, the study also showed that there was a strong link with the APOE ε4 allele and the presence of lobar microbleeds.

"As in Alzheimer disease, the APOE ε4 allele is a known risk factor for lobar ICH and CAA. . . . Although the exact molecular mechanism is not clear, APOE ε4 carriership is presumed to lead to hemorrhage by increased vascular deposition of β-amyloid," the authors write.

However, the APOE ε4 genotype was not associated with deep or infratentorial microbleeds. Instead they found high systolic blood pressure and smoking were associated with lesions in this region.

"The high prevalence of cerebral microbleeds in our study as well as the finding that risk factors vary according to microbleed location has major importance in view of previous reports from small clinical series suggesting that microbleeds may reflect an increased risk of recurrence of stroke and hemorrhagic transformation of ischemic stroke," the authors write.

The study was supported by the Erasmus MC University Medical Center and Erasmus University Rotterdam, the Netherlands Organization for Scientific Research, and the Netherlands Organization for Health Research and Development.

Neurology. 2008;70:208-1214.

    
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