Patients with cerebral small vessel disease (SVD) can present as isolated lacunar infarction or with diffuse white matter changes, with the imaging appearance of leukoaraiosis. Endothelial dysfunction, which can lead to breakdown of the blood-brain barrier, impaired cerebral autoregulation and prothrombotic changes, is believed to be important in mediating disease. Circulating levels of intercellular adhesion molecule 1 (ICAM1), thrombomodulin (TM), tissue factor (TF) and tissue factor pathway inhibitor (TFPI) are markers of endothelial activation and damage, and may provide insights into disease pathogenesis or differences between phenotypes. We therefore measured these markers in a prospective series of patients with lacunar stroke. One hundred and ten white Caucasian patients with previous lacunar stroke and 50 community control subjects were studied. Markers of endothelial function were measured on venous blood samples. Patients were classified on brain imaging into two groups: isolated lacunar infarction (n = 47) and ischaemic leukoaraiosis, defined as a clinical lacunar stroke and leukoaraiosis on brain imaging (n = 63). The number of lacunes and severity of leukoaraiosis were also scored on MRI. ICAM1, TM and TFPI were elevated in cerebral SVD subjects compared with controls (P

Ischaemic stroke can be caused by a number of monogenic disorders, and in such cases stroke is frequently part of a multisystem disorder. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL), due to mutations in the NOTCH: 3 gene, is increasingly appreciated as a cause of familial subcortical stroke. The genetics and phenotypes of monogenic stroke are covered in this review. However, the majority of cases of ischaemic stroke are multifactorial in aetiology. Strong evidence from epidemiological and animal studies has implicated genetic influences in the pathogenesis of multifactorial ischaemic stroke, but the identification of individual causative mutations remains problematic; this is in part limited by the number of approaches currently available. In addition, genetic influences are likely to be polygenic, and ischaemic stroke itself consists of a number of different phenotypes which may each have different genetic profiles. Almost all human studies to date have employed a candidate gene approach. Associations with polymorphisms in a variety of candidate genes have been investigated, including haemostatic genes, genes controlling homocysteine metabolism, the angiotensin-converting enzyme gene, and the endothelial nitric oxide synthase gene. The results of these studies, and the advantages and limitations of the candidate gene approach, are presented. The recent biological revolution, spurred by the human genome project, promises the advent of novel technologies supported by bioinformatics resources that will transform the study of polygenic disorders such as stroke. Their potential application to polygenic ischaemic stroke is discussed.

Cerebral small vessel disease (SVD) causes focal lacunar infarction and more diffuse ischaemia, referred to as leukoaraiosis. Endothelial dysfunction has been proposed as a causal mechanism in the disease. Homocysteine is toxic to endothelium. We determined whether elevated homocysteine levels and the methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism are risk factors for SVD as a whole, and for two different SVD subtypes: isolated lacunar infarction and ischaemic leukoaraiosis. We also determined whether any association was mediated by endothelial dysfunction, as assessed by circulating endothelial markers. One hundred and seventy-two Caucasian patients with SVD and 172 community controls of similar age and sex were studied. Serum homocysteine measurement and MTHFR genotyping was performed. Levels of intercellular adhesion molecule 1 (ICAM1) and thrombomodulin were measured in a subgroup. Mean homocysteine levels were higher in SVD than controls [14.55 micromol/l [95% confidence interval (CI) 13.78-15.35] versus 12.01 micromol/l (95% CI 11.42-12.64), P < 0.0005]. Homocysteine was a stronger risk factor in those with ischaemic leukoaraiosis [12.92 (95% CI 4.40-37.98), P < 0.0005) per micromol increase in log homocysteine concentration (P < 0.0005)] in comparison with isolated lacunar infarction [4.22 (95% CI 1.29-13.73), P = 0.02] after controlling for both conventional risk factors and age. The MTHFR 677T allele was a risk factor only in the ischaemic leukoaraiosis group [odds ratio (OR) 2.02 (95% CI 1.31-3.1), P = 0.001]. Inclusion of the endothelial markers ICAM1 and thrombomodulin in a logistic regression model resulted in the association between homocysteine and SVD no longer being significant. In conclusion, hyperhomocysteinaemia is an independent risk factor for SVD, particularly ischaemic leukoaraiosis, and this effect may be mediated via endothelial dysfunction. Homocysteine-lowering therapy may be particularly effective in this subgroup.