PubMed Health⌕ Search

Biomedical subjects

Ka Sing Wong

Publications and source records attributed to Ka Sing Wong.

At least 19 recordsLinked to original sources
PubMed2006

Total cerebral blood flow estimated by color velocity imaging quantification ultrasound: a predictor for recurrent stroke?

Although the Virchow's triad on thrombosis includes reduced blood flow as a factor, there has been relatively little data on the importance of total cerebral blood flow on the risk of subsequent stroke. In the current study, we investigate whether total cerebral blood flow helps predict stroke recurrence. Extracranial arterial blood flow volume estimated by color velocity imaging quantification ultrasound (CVIQ) is an index of cerebral blood flow measurement. We performed a cohort study of 210 consecutive acute stroke patients. Patients were studied with transcranial Doppler and duplex ultrasound for intra- and extracranial large artery disease within 3 days of symptom onset. The association between the risk of recurrent stroke and CVIQ was analyzed with Cox proportional hazards model. Thirty-nine patients (17.7%) developed an ischemic stroke during a mean follow-up of 47.5 months. The mean extracranial blood flow volume was significantly lower for patients who had a recurrent stroke than those without (594.4+/-130.3 versus 683.8+/-176.9 mL/min; P=0.003). In a Cox proportional hazards model adjusting for potential confounding variables, extracranial blood flow volume (hazard ratio (HR) for lowest tertile, 4.1; 95% confidence interval (CI), 1.5 to 11.0) along with male sex (HR, 2.5; 95% CI, 1.3 to 5.1), diabetes (HR, 2.5; 95% CI, 1.2 to 5.0) and large artery stenosis (HR, 2.2; 95% CI, 1.1 to 4.4) were independent predictors for stroke recurrence. Our data indicated that patient with low amount of blood flow to the brain is at risk of recurrent stroke.

Aged↗
PubMed2006

Comparison of plasma beta-globin DNA and S-100 protein concentrations in acute stroke.

BACKGROUND: This study aimed to compare changes in plasma beta-globin DNA and serum S100 protein to diagnose stroke and for predicting mortality and morbidity. METHODS: Patients with stroke-like symptoms presenting to the emergency department of a Hong Kong hospital were recruited. Plasma DNA was analyzed for the beta-globin gene with fluorescent-based PCR. S100 concentrations were determined using ELISA. Primary outcomes were diagnosis of stroke, mortality, and modified Rankin Score (mRS) after 6 months. RESULTS: One hundred ninety-seven consecutive patients recruited, 118 (60%) ischemic stroke, 35 (18%) hemorrhage and 44 (22%) with no acute neuroimaging changes. Serum S100 and plasma DNA were increased in 126 (p<0.0010) and 36 (p=0.21) stroke patients respectively vs. controls. Median plasma DNA was higher in hemorrhagic stroke than those without (1725 vs. 1050 kilogenome-equivalents/l, p=0.0104). Median plasma DNA was higher in mRS>2 vs. mRS 2 patients vs. mRS<or=2 (0.152 vs. 0.131 microg/l, p=0.0003). The odds ratio (OR) of discriminating hemorrhagic from non-hemorrhagic stroke with DNA was 4.24 (95% CI 1.88-9.56); S100 and DNA together give an OR of 16.55. CONCLUSION: For stroke diagnosis, S100 performs better than DNA; DNA is a better marker for hemorrhage. For diagnosis of hemorrhagic stroke, combined S100 and DNA performs better than either alone. Plasma DNA and serum S100 predict morbidity and mortality in stroke.

Adult↗
PubMed2006

Apolipoprotein E epsilon4 allele is associated with vascular dementia.

BACKGROUND/AIMS: The apolipoprotein E (ApoE) exon 4 polymorphism has been associated with vascular dementia (VaD) risk. Since not all studies confirm this finding, we explored this association in a case-control study. METHODS: We genotyped ApoE in 144 VaD patients and 251 controls. RESULTS: VaD patients were more likely than controls to have ApoE epsilon3/epsilon4 or epsilon4/epsilon4 genotypes: 23.6% versus 15.1%, odds ratio (OR) = 1.7, p = 0.036. This association remained significant after adjustment for age, sex, hypertension and diabetes by multiple logistic regression: OR = 1.9, p = 0.030. The association of epsilon3/epsilon4 or epsilon4/epsilon4 genotypes with VaD was strong among people with hypertension (OR = 2.9, p = 0.007) or diabetes (OR = 6.5, p = 0.011). The association was absent among people without hypertension (OR = 1.1, p = 0.79) or diabetes (OR = 1.3, p = 0.43). CONCLUSION: This interaction with hypertension and diabetes should be examined in other studies to confirm or refute this observation.

Aged↗
PubMed2006

Paraoxonase 1 gene Q192R polymorphism affects stroke and myocardial infarction risk.

OBJECTIVES: Paraoxonase (PON1), an enzyme associated with high-density lipoprotein (HDL) particles, inhibits oxidation and atherogenesis. We sought to investigate the association of the PON1 Q192R polymorphism with stroke and heart disease. DESIGN AND METHODS: In a case control study, we genotyped 242 ischemic stroke, 231 myocardial infarction (MI), and 310 healthy control subjects, all Chinese. RESULTS: R-containing genotypes (R+) were associated with vascular disease, OR = 1.5, P = 0.03. RR was increased in MI patients who were either smokers (OR = 3.1, P = 0.01), male, or younger than 60. R+ but not RR genotypes were increased in stroke patients, particularly large artery type (OR = 2.6 and P = 0.02 for R+, OR = 1.0 for RR) or among smokers. The relative dearth of RR in stroke might be due to earlier MI or death in at-risk people, such as smokers. R+ genotypes were increased with stroke in hypertensive (OR = 2.1, P = 0.02) but not normotensive (OR = 1.0) subjects. CONCLUSIONS: PON1 192R+ genotypes were associated with stroke and MI, particularly in subsets of patients, in patterns suggesting a possible survivor effect.

Aged↗
PubMed2006

Efficacy of dual antiplatelet therapy in cerebrovascular disease as demonstrated by a decline in microembolic signals. A report of eight cases.

BACKGROUND: The presence of microembolic signals (MES) may indicate an increased risk of recurrent ischemic events in patients with stroke. The optimal management of such patients is uncertain. We report the effect of clopidogrel in addition to aspirin on the number of MES in a series of patients with ischemic stroke and transient ischemic attack (TIA) due to large-vessel disease. METHODS: 8 patients with either extracranial or intracranial artery stenosis were identified in 30-min MES studies by transcranial Doppler sonography as having MES. All patients were on antiplatelet therapy prior to baseline transcranial Doppler monitoring. The patients were subsequently treated with clopidogrel in addition to aspirin. Repeat MES studies were performed between day 3 and 7 with aspirin and clopidogrel. RESULTS: All patients were Chinese. The median interval time from symptom onset to initial MES study was 7 days (range of 2-30). MES donor sites included 4 severely stenosed or occluded internal carotid arteries and 4 stenosed middle cerebral arteries. The median MES number at baseline was 8 (range 3-51). Repeat MES studies showed a significant decrease in MES (p = 0.012, Wilcoxon signed ranks test). 4 patients had complete cessation of MES and all patients showed a decline in MES. No patient had recurrent strokes or bleeding complications. CONCLUSION: The rapid and significant decline of MES in our stroke and TIA patients suggests the possible efficacy of dual antiplatelet therapy with aspirin and clopidogrel in patients with MES and symptomatic large-artery occlusive disease. Randomized controlled trials should be conducted to confirm this preliminary observation.

Aged↗
PubMed2006

Is hypoperfusion an important cause of strokes? If so, how?

Traditionally hypoperfusion and embolism are considered separate important causes of stroke in patients with arterial occlusive disease. However, although hypoperfusion and embolism differ in mechanisms and location, they generally coincide in severe obstructive lesions and cause washout disturbances of embolism in low perfusion territories distal to stenosis. Unless the collateral blood supply is sufficient to prevent ischemia, multiple remote spot-like infarctions occur within the hypoperfused brain territory. In border-zone distributed infarction - long suspected to result from hemodynamic compromise alone - complementary interaction of embolisation and hypoperfusion territories has to be considered. Thus hypoperfusion with embolism or embolism alone are the most common explanations for stroke, the former often associated with less severe clinical deficits than the latter.

Arterial Occlusive Diseases↗
PubMed2006

Topographic patterns of small subcortical infarcts associated with MCA stenosis: a diffusion-weighted MRI study.

BACKGROUND AND PURPOSE: Small subcortical infarcts (SSI, maximum lesion diameter < or =2.0 cm) are usually considered as infarcts caused by small vessel disease. However, SSI can also be associated with large artery occlusive disease such as middle cerebral artery (MCA) stenosis. We performed a prospective study to investigate the relationship between MCA stenosis and SSI distribution and further to investigate the mechanism of SSI caused by MCA stenosis. METHODS: Magnetic resonance angiography (MRA) and diffusion-weighed MRI (DWI) of consecutive acute ischemic stroke patients with recent SSI were studied. The distribution of acute infarcts on DWI was categorized as cortical infarct (CI), border zone infarct (BI), or perforating artery infarct (PAI). RESULTS: Totally, 93 cases were recruited, among which 12 had single SSI with MCA stenosis (group 1) and 26 patients had multiple SSI with MCA stenosis (group 2), while 55 patients without MCA stenosis had single SSI (group 3). For patients with single SSI and MCA stenosis, 6 had BI and 6 had PAI; for patients with multiple SSI and MCA stenosis, 25 had BI, 4 had PAI and 9 had CI (compared with group 1: P= .001); for patients with single SSI but without MCA stenosis, 20 had BI and 35 had PAI (compared with group 1: P= .58). CONCLUSION: Multiple acute infarcts along the border zone are the commonest pattern in small infarcts with MCA stenosis, especially among those with multiple acute infarcts. Our data suggest that hemodynamic compromise and artery-to-artery embolism may be both important factors for infarcts in patients with MCA stenosis.

Aged↗
PubMed2006

Relationship between cerebral vasomotor reactivity and white matter lesions in elderly subjects without large artery occlusive disease.

BACKGROUND AND PURPOSE: The relationships between cerebral vasomotor reactivity (CVR) and white matter lesions (WMLs) were investigated mainly in patients with carotid stenosis. We aimed to study the relationship in asymptomatic elderly subjects without large artery occlusive disease. METHODS: A total of 33 elderly individuals (mean age was 76.2 years) who were free from neurological deficit or cognitive impairment were studied. Bilateral mean blood flow velocity was measured in the middle cerebral artery using a 2-MHz pulsed transcranial Doppler (TCD) system together with intravenous administration of acetazolamide as vasodilatory stimuli. WMLs on a fluid-attenuated inversion recovery (FLAIR) sequence of MRI were classified into two categories: subcortical deep white matter hyperintensity (SDWMH) and periventricular hyperintensity (PVH). The lesions in each category were then divided into three grades (grade 0-I, grade II, grade III) according to the Fazekas scale. RESULTS: CVR was inversely associated with the extent of SDWMH and PVH. The differences in CVR were statistically significant among different severity of WMLs: for SDWMH (70%+/- 10% in grade 0-I, 60%+/- 10% in grade II, and 40%+/- 10% in grade III, P < .001); for PVH (80%+/- 10% in grade 0-I, 60%+/- 10% in grade II, and 40%+/- 10% in grade III, P < .001). CONCLUSIONS: Impaired CVR is related to the extent of WMLs in asymptomatic elderly individuals without large artery stenosis. The findings in our study suggest that dysfunction of cerebral vascular autoregulation might be an important factor in the development of WMLs in the asymptomatic elderly without large artery occlusive disease.

Acetazolamide↗
PubMed2006

Diagnostic accuracy of MRI for middle cerebral artery stenosis: a postmortem study.

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI) has been widely applied in detecting intracranial large artery stenosis, but there have been few validation studies to compare with histopathology. The aim of the postmortem study is to assess the accuracy of MRI in identifying middle cerebral artery (MCA) stenosis. METHODS: We recruited, consecutively, Chinese postmortem autopsies in our hospital during 19 months. MRI was performed in the postmortem brains to scan the cross-sections of MCAs with barium expanding the artery lumen. The MCAs were then removed for histopathologic studies. With histopathology as a reference standard, the accuracy of MRI was evaluated, and the correlation between MCA stenosis identified by MRI and radiologically or histopathologically evident brain infarcts was investigated. RESULTS: Seventy-six consecutive autopsies were recruited. The sensitivity and specificity of MRI in detecting more than 30% MCA stenosis were 38.6% and 92.2%, with a positive predictive value of 87.2% and negative predictive value of 52.2%, and the corresponding values of MRI in identifying more than 50% MCA stenosis were 57.1%, 90.8%, 50%, and 83.0%, respectively. Both more than 30% and more than 50% MCA stenosis identified by MRI were found to be associated with infarctions in the corresponding MCA territory (P= 0.001, odds ratio = 4.365, 95% CI: 1.684-11.313; and P= 0.039, odds ratio = 2.694, 95% CI: 1.139-6.377). CONCLUSIONS: Our study demonstrates the agreement between ex vivo MRI and histopathology in identifying MCA stenosis, and the correlation between the MCA stenosis identified by MRI and radiologically or histopathologically evident brain infarcts.

Aged↗
PubMed2006

Frequency and clinical determinants of poststroke cognitive impairment in nondemented stroke patients.

The objective of this study was to examine the prevalence and clinical correlates of poststroke cognitive impairment in Chinese stroke patients in Hong Kong. One hundred seventy-nine stroke patients were interviewed by a psychiatrist 3 months after their stroke. Cognitive impairment was determined according to the Mini-Mental State Examination score. Thirty-nine participants (21.8%) had cognitive impairment. Univariate analysis found that cognitive impairment was associated with age, female sex, level of education, previous stroke, prestroke Rankin score, National Institutes of Health Stroke Scale dysarthria and total scores, urinary incontinence, and cerebral atrophy index. Multivariate logistic regression suggested that female sex, education, National Institutes of Health Stroke Scale dysarthria score, urinary incontinence, and atrial fibrillation were independent risk factors of poststroke cognitive impairment. After removal of 54 patients with previous stroke from the sample, the frequency of cognitive impairment decreased to 18.4%. It was concluded that cognitive impairment is common among nondemented Chinese stroke patients in Hong Kong.

Age Factors↗
PubMed2006

Associations of apolipoprotein E exon 4 and lipoprotein lipase S447X polymorphisms with acute ischemic stroke and myocardial infarction.

BACKGROUND: Because apolipoprotein E (apoE) and lipopoprotein lipase (LPL) polymorphisms interact with each other and with other factors to affect lipid metabolism, we sought to determine their separate and combined effects in association with ischemic vascular disease. METHODS: We performed a case-control study of 816 subjects: 246 acute ischemic stroke patients, 234 acute myocardial infarction patients, and 336 controls. APOE exon 4 and LPL S447X genotypes were determined. RESULTS: APOE epsilon2 and epsilon4 homozygotes were increased in stroke (4.5% vs. 1.0%, p = 0.008), while in myocardial infarction the epsilon4 allele was increased (12.6% vs. 9.5%, p = 0.006) but epsilon2 was decreased (3.7% vs. 12.1%, p = 0.000006). For subjects with either APOE epsilon2 or epsilon4 alleles, LPL X alleles were increased in vascular disease (OR = 2.2, p = 0.01). LPL X alleles displayed opposite tendencies toward association with disease when subjects were divided by sex, smoking, or APOE genotype. Meta-analysis and regression analysis of previous studies supported the sex and smoking dichotomies. CONCLUSION: This is the first report of an association of vascular disease with an interaction of APOE exon 4 and LPL S447X genotypes. Therefore, APOE genotypes and LPL S447X interactions with apoE, sex, and smoking may affect the risk of myocardial infarction and ischemic stroke.

Aged↗
PubMed2005

The frequency and determinants of calcification in intracranial arteries in Chinese patients who underwent computed tomography examinations.

BACKGROUND: Intracranial artery calcification is common but the prevalence and determinants are not well established. We aim to describe the prevalence and location of calcification in intracranial arteries according to brain multi-detector-row computed tomography (MDCT) images, and to investigate its correlation with potential risk factors. METHODS: We studied consecutive men and women referred for brain CT in December 2004. All patients received a questionnaire regarding their medical history related to atherosclerosis, including traditional risk factors of atherosclerosis, serum chemistry values and inflammatory markers. All CT examinations were done with a 16-slice MDCT and the severity of intracranial artery calcification was categorized. RESULTS: Four hundred and ninety patients aged 1.4-101 years (62.92+/-19.04; mean+/-SD) were included in our study. There were 340 patients (69.4%) who had intracranial artery calcification. The highest prevalence of intracranial artery calcification was seen in the internal carotid artery (60%), followed by vertebral artery (20%), middle cerebral artery (5%) and basilar artery (5%). Patients with calcification were significantly older than those without calcification (p<0.001). A significantly higher prevalence of calcification was present among patients with hypertension (p<0.001), diabetes (p<0.001), renal failure (p<0.05), atrial fibrillation (p<0.05), smoking (p<0.05), hyperlipidemia (p<0.001), ischemic heart disease (p<0.05) and ischemic stroke (p<0.001). Mean values of serum phosphate, serum urea and CRP level were also significantly higher in patients with intracranial artery calcification (p<0.05, respectively), and there was a trend that patients with intracranial calcification had a higher white blood cell count (p=0.070). Stepwise multiple logistic regression showed age (RR=2.795 per 10 years), a history of ischemic stroke (RR=3.915), and white blood cell count (RR=1.107) to be independently associated with intracranial artery calcification. CONCLUSIONS: Calcification of the intracranial arteries is associated with age, history of ischemic stroke and white blood cell count. Further prospective studies to investigate the clinical significance of intracranial artery calcification are needed.

Adolescent↗
PubMed2005

Hyperhomocysteinemia is associated with volumetric white matter change in patients with small vessel disease.

BACKGROUND: Hyperhomocysteinemia is associated with cerebral small vessel disease (SVD). We examined the relationship between homocysteine and 1) volumetric measure of white matter change (WMC), 2) silent brain infarcts, 3) cerebral atrophy on MRI and 4) cognition on a consecutive cohort of patients with stroke associated with SVD. SUBJECTS AND METHODS: Fifty-seven patients consecutively admitted to the Acute Stroke Unit in a university hospital due to stroke associated with SVD were recruited and assessed three months after the stroke. Non-fasting homocysteine was obtained. Using MRI, the number of infarcts, volume of WMC and cerebral atrophy were measured. General cognitive functions were assessed using the Mini Mental State Examination and Alzheimer's disease Assessment Scale. Mattis Dementia Rating Scale - Initiation/Perseveration subset was used to assess executive cognitive functions. RESULTS: Hyperhomocysteinemia (> or = 14.88 micromol/L) significantly accounted for the volume of WMC on MRI in a multivariate stepwise regression model (adjusted R(2)=0.058, p <0.05) after adjustment for age and folate level. Patients in the highest quartile of WMC volume had significantly higher levels of homocysteine than those in lowest quartile (p <0.001). No significant relationship was found between homocysteine and silent brain infarcts, cerebral atrophy and performance on psychometric tests. CONCLUSION: Hyperhomocysteinemia is associated with volumetric measure of WMC among patients with SVD. The role of homocysteine in the development of silent brain infarcts and cerebral atrophy as previously reported cannot be ascertained in this study. No direct relationship was found between homocysteine and cognitive functions.

Aged↗
PubMed2005

Determinants of prestroke cognitive impairment in stroke associated with small vessel disease.

Understanding the determinants of prestroke cognitive impairment (PCI) in stroke associated with small vessel disease (SVD) may shed light on how to prevent further cognitive deterioration after stroke. We administered the Informant Questionnaire on Cognitive Decline (IQCODE) to close informants of 78 consecutive stroke patients who had SVD. PCI, as defined by an average score of IQCODE > or =3.4 was found in 19 (24%) patients. Regression analyses were performed on the following risk factors for PCI: age, years of education, gender, previous stroke, volume of white matter changes, measures of silent lacunes, cerebral atrophy index, medial temporal lobe atrophy and frontal lobe atrophy. Multivariate regression analyses revealed that only cerebral atrophy index (OR 1.5, CI 1.2-1.9, p < 0.001) predicted PCI among patients with SVD.

Aged↗
PubMed2005

Myopathic changes associated with severe acute respiratory syndrome: a postmortem case series.

BACKGROUND: The March 2003 outbreak of the severe acute respiratory syndrome (SARS) resulted in significant morbidity and mortality. Muscle weakness and elevated serum creatine kinase levels are commonly encountered in patients with SARS. However, the nature and cause of myopathy associated with a SARS infection are unknown because, to our knowledge, there has been no report of histological or postmortem examination of the skeletal muscle from SARS-infected patients. OBJECTIVE: To determine the exact nature of the myopathy associated with SARS. METHOD: Postmortem skeletal muscles from 8 consecutive patients who died of SARS in March 2003 were studied under light and electron microscopy as well as immunohistochemistry. RESULTS: Focal myofiber necrosis was identified in 4 of 8 cases. Macrophage infiltration and regenerative fiber were scanty. All 4 patients treated with a steroid had significant myofiber atrophy. In situ hybridization for coronavirus was negative in all subjects. Viral cultures for coronavirus and examination for viral particles under electron microscopy were performed in 2 patients. The viral culture yielded no organisms and there were no viral particles seen on electron microscopic examination. CONCLUSIONS: There is a spectrum of myopathic changes associated with a SARS infection. Focal myofiber necrosis is common and possibly is immune mediated. Critical illness myopathy and superimposed steroid myopathy may also play an important role in SARS.

Adult↗
PubMed2005

Screening of dementia in stroke patients with lacunar infarcts: comparison of the mattis dementia rating scale and the mini-mental state examination.

There have been no data on the performance of the Initiation-Perseveration subtest of the Mattis Dementia Rating Scale (MDRS-IP) in screening poststroke dementia (PSDE). Three months after the index stroke, a research assistant administered the MDRS-IP and Mini-Mental State Examination (MMSE) to 83 Chinese stroke patients with lacunar infarcts who were consecutively admitted to the stroke unit of a general hospital. A psychiatrist, who was blind to the MDRS-IP and MMSE scores, interviewed all 83 patients and made a Diagnostic and Statistical Manual of Mental Disorders (4th edition) diagnosis of dementia, which served as the benchmark for judging the performance of MDRSIP. The optimal cutoff point of MDRS-IP was 22/23. The sensitivity, specificity, and positive and negative predictive values of MDRS-IP, and the area under the receiver operating characteristic curve were 82%, 90%, 0.41, 0.98, and 0.91, respectively. The overall performance of the MDRS-IP was comparable to the MMSE.

Activities of Daily Living↗
PubMed2005

Poststroke depression in Chinese patients: frequency, psychosocial, clinical, and radiological determinants.

This study attempted to evaluate the psychosocial, clinical, and radiological predictors of poststroke depression (PSD) in Chinese patients. One hundred eighty-nine patients participated in the study. Three months after the index stroke, a psychiatrist administered the Structured Clinical Interview for DSM-IV to all of the patients and made a DSM-IV diagnosis of depression. In addition, a host of demographic, clinical, and radiological variables were examined. Thirty-one (16.4%) of the patients had a diagnosis of PSD that included major depression (n=11, 5.8%,), minor depression (n=16, 8.5%), or dysthymia (n=4, 2.1%). Univariate analysis revealed that PSD was associated with female gender, a lower level of education, a lower Lubben Social Network Scale (LSNS) score, subcortical infarcts, and lesions in the anterior cerebral artery (ACA) territory, and the Modified Life Event Scale (MLES) score was borderline for statistical significance. Multivariate logistic regression analysis suggested that female gender, a high MLES score, and subcortical and ACA lesions were independent risk factors for PSD and that a high LSNS score was a protective factor.

Aged↗