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Biomedical subjects

Ka Sing Wong

Publications and source records attributed to Ka Sing Wong.

11 recordsLinked to original sources
PubMed2003

Cerebral microbleeds as a risk factor for subsequent intracerebral hemorrhages among patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Cerebral microbleeds (MBs) detected by gradient-echo MRI are considered evidence of advanced microangiopathy with potential for further bleeding. The goal of this study was to determine whether the presence of MBs is a risk factor for subsequent intracerebral hemorrhage among patients with acute ischemic stroke. METHODS: We prospectively examined patients hospitalized with acute cerebral infarction with gradient-echo T2*-weighted MRI for the presence of MBs. We recorded demographics, medical history, and stroke severity. Patients were then followed up for the development of stroke, other vascular events, and death. RESULTS: One hundred twenty-one consecutive patients with a mean age of 67.96+/-10.97 years were recruited. MBs were present in 43 patients (35.5%). During follow-up of 27.15+/-11.68 months, 16 patients had recurrent stroke. There was no difference between patients with or without MB for the development of ischemic stroke (5 and 6 respectively, P=0.841). However, 4 patients (9.3%) with MBs and 1 patient (1.3%) without an MB had intracerebral hemorrhage during follow-up (P=0.053). Of the 5 patients who developed subsequent intracerebral hemorrhages, 3 were treated with aspirin and 2 with anticoagulation. Two of the intracerebral hemorrhages occurred in the site where asymptomatic MBs were found at baseline. CONCLUSIONS: MBs appear to be a risk factor for subsequent intracerebral hemorrhage among patients with ischemic stroke in this small cohort of Chinese stroke patients. A large cohort study is required to confirm this observation.

Acute Disease↗
PubMed2003

Long-term mortality and recurrent stroke risk among Chinese stroke patients with predominant intracranial atherosclerosis.

BACKGROUND AND PURPOSE: The goal of this study was to document the long-term outcome of ischemic stroke patients in a population with predominant intracranial atherosclerosis and risk factors for a recurrent event. METHODS: Intracranial and extracranial arteries of consecutive patients with acute ischemic stroke were studied prospectively with transcranial Doppler and duplex ultrasound. All patients were followed up regularly for the development of recurrent stroke, cardiac event, or death. RESULTS: We included 705 patients with acute ischemic stroke, of whom 345 were documented ultrasonographically as having large-artery lesions. The follow-up period was up to 42 months (mean, 28+/-5 months). One hundred seventeen patients (17%) died of any cause, and 199 (28%) suffered further cerebrovascular cardiac events. The 3.5-year cumulative mortality rate was 20.8%; for cerebrovascular event, it was 29.5%. The annual recurrent stroke rates during the first year were 10.9% for patients without vascular lesion, 17.1% for intracranial atherosclerosis only, and 24.3% for both intracranial and extracranial atherosclerosis; for the second year, the rates were 7.5%, 8.6%, and 7.7%, respectively. More occurrence of death (log rank, 5.19; P=0.02) or cerebrovascular event (log rank, 9.68; P=0.002) was found among patients with than those without vascular lesions. Patients with both intracranial and extracranial arterial lesions were at highest risk of death (log rank, 9.64; P=0.008) and cerebrovascular event (log rank, 11.56; P=0.003). When death and further vascular event were combined as poor outcomes in a Cox proportional-hazards regression model, number of abnormal arteries, advanced age, diabetes, atrial fibrillation, and previous stroke were significant predictors. CONCLUSIONS: Patients with intracranial atherosclerosis, especially coexisting extracranial carotid disease, are at higher risk of suffering death or further vascular event. Our findings provide important data for planning future randomized clinical trials for this high-risk group of stroke patients.

Aged↗
PubMed2003

Relationship between the Oxfordshire Community Stroke Project classification and vascular abnormalities in patients with predominantly intracranial atherosclerosis.

BACKGROUND: The Oxfordshire Community Stroke Project (OCSP) classification is a stroke classification based on clinical features collected at bedside. Previous studies reported good correlation between vascular abnormalities and OCSP mainly in populations not at risk of intracranial atherosclerosis. There have been limited data on the relationship between intracranial atherosclerosis and the OCSP classification. METHODS: Consecutive Chinese patients admitted to a regional hospital with acute ischemic stroke were studied in Hong Kong. Stroke subtype was classified as total or partial anterior circulation infarct (TACI or PACI), posterior circulation infarct (POCI), or lacunar infarct (LACI), according to the OCSP method. Transcranial Doppler (TCD) was performed whenever possible to evaluate the intracranial arteries as well as the carotid arteries. National Institute of Health Stroke Scale (NIHSS) was used to assess the severity of stroke on admission. RESULTS: Six hundred and ninety-nine consecutive patients were studied. On admission, 24 patients were classified as TACI (3.4%), 96 PACI (13.7%), 111 POCI (15.9%), and 468 LACI (67.0%). Of the 345 patients who had TCD evidence of intracranial or carotid artery abnormalities, 75% had intracranial involvement only, 5% extracranial involvement only and 20% had both intracranial and extracranial involvement. The frequencies of arterial abnormalities were found in 58% of TACIs, 48% of PACIs, 48% of POCIs and 50% of LACIs. There was no evidence that the frequencies of arterial abnormalities were different between the OCSP groups (P=0.8). Middle cerebral artery velocity was abnormal in 9 TACIs (38%), 32 PACIs (33%), 35 POCIs (32%) and 177 LACIs (38%) (P=0.6). Vertebrobasilar velocities were abnormal in 4 TACIs (17%), 20 PACIs (21%), 29 (26%) and 87 LACIs (19%) (P=0.3). The OCSP subtypes were associated with POCIs the severity of stroke. NIHSS score of > or =9 was found in 83% of TACIs, 18% of PACIs, 9% of POCIs, and 12% of LACIs (P<0.0001). CONCLUSIONS: OCSP classification is not significantly related to the presence of vascular abnormalities among patients with predominantly intracranial atherosclerosis.

Aged↗
PubMed2003

Can IQCODE detect poststroke dementia?

BACKGROUND: Little is known about the performance of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) in the screening of post-stroke dementia (PSDE). METHODS: At 3 months after the index stroke, a research assistant administered the IQCODE to relatives of 189 Chinese patients with acute stroke who were consecutively admitted to a general hospital. A psychiatrist, who was blind to the IQCODE scores, interviewed all 189 patients and made DSM-IV diagnosis of dementia, which served as the benchmark for judging the performance of IQCODE in screening PSDE. RESULTS: The optimal cut-off point of IQCODE was 3.40. The sensitivity, specificity, and positive and negative predictive values of IQCODE, and the area under the receiver operating characteristic curve, were 88%, 75%, 33%, 98%, and 0.88, respectively. CONCLUSIONS: When used as a sole instrument, IQCODE does not appear to be useful in screening PSDE in Chinese elderly.

Aged↗
PubMed2003

Middle cerebral artery stenosis in type II diabetic Chinese patients is associated with conventional risk factors but not with polymorphisms of the renin-angiotensin system genes.

BACKGROUND: Conventional and genetic risk factors have been reported to play a role in the pathogenesis of ischaemic stroke, and differences may explain the heterogeneity of disease presentation in different populations. In Chinese, middle cerebral artery (MCA) stenosis is the most commonly identified intracranial vascular lesion. The involvement of renin-angiotensin system (RAS) gene polymorphisms in this condition has not been determined. OBJECTIVES: To determine whether conventional and RAS genetic vascular risk factors are associated with MCA stenosis, asymptomatic Chinese type II diabetic patients with and without MCA stenosis matched for age, gender and diabetes duration were compared. METHODS: Biochemical parameters and the genotype and allele frequencies of three RAS gene polymorphisms, the angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen (AGT) M235T and angiotensin II type 1 receptor (AT(1)R) A1166C polymorphisms were then compared between 217 diabetics with and 490 matched diabetic controls without MCA stenosis selected from 2,202 diabetics. RESULTS: MCA stenosis was associated with significantly increased systolic blood pressure, LDL-cholesterol and albuminuria, yet diastolic blood pressure and glucose levels were lower. There was an increased prevalence of hypertension and use of blood pressure-lowering agents in the MCA stenosis patients. Albuminuria was also more commonly found in these patients. Hypertensive status, systolic blood pressure and albuminuria were strong, independent predictors of the presence of MCA stenosis. No differences in the RAS polymorphism distributions were observed between patients with and without MCA stenosis. CONCLUSIONS: In these asymptomatic type II diabetics, blood pressure indices and albuminuria, but not RAS gene polymorphism, were closely associated with MCA stenosis.

Aged↗
PubMed2003

Characteristics of microembolic signals detected near their origins in middle cerebral artery stenoses.

BACKGROUND AND PURPOSE: Usually, microembolic signal (MES) monitoring is performed for MESs arising from downstream sources. The aim of this study is to describe the special characteristics of MESs originating from nearby sources in the middle cerebral artery (MCA). METHODS: We analyzed 265 MESs detected in 5 patients (the study group) who had acute ischemic strokes within the territory of MCA stenoses and 48 MESs detected in 7 patients (the control group) from proximal sources: severe internal carotid artery stenoses and prosthetic heart valves. MESs were recorded with a 2-MHz, bigate transducer. We performed offline analyses of the recorded MESs using both post-fast Fourier transform (FFT) spectra and pre-FFT time domain signals. MESs were divided into 3 types--focused-frequency signals (FFSs), bottom-frequency signals (BFSs), and multifrequency signals (MFSs)--according to the frequencies of the signals displayed on the post-FFT spectra. RESULTS: In the study group, among 265 MESs, 245 (92.5%) were MFSs, 11 (4.2%) were FFSs, and 9 (3.4%) were BFSs. In the control group, among 48 MESs, 45 (93.5%) were FFSs, 2 (4.2%) were MFSs, and 1 (2.%) was a BFS. There was significant difference in MES type between MCA stenoses and other embolic sources (P < .05). On the post-FFT spectra, MFSs recorded from MCA stenoses occupied multiple frequencies along the vertical axis, and the low-frequency parts were usually bidirectional. On the pre-FFT time domain signals, the highest frequency parts presented distorted, amplitude-modulated sine waves, and the low-frequency parts presented totally irregular waves. The amplitudes of the low-frequency parts diminished with time in the proximal channel but enlarged with time in the distal channel over a short period. CONCLUSION: MESs recorded from MCA stenoses may have special characteristics of multiple frequencies on both post-FFT spectra and pre-FFT time domain signals. Our findings may represent rotating or vibrating emboli as they are just dislodged from the thrombus and are moving from the vessel wall to the center. Further clinical and laboratory studies are needed to confirm this hypothesis.

Aged↗
PubMed2003

Variability and validity of a simple visual rating scale in grading white matter changes on magnetic resonance imaging.

BACKGROUND AND PURPOSE: A new simple visual rating scale can be used in magnetic resonance imaging (MRI) to grade the severity of white matter changes (WMC). The authors sought to study the interobserver variability and the validity of this visual rating scale against a computer-aided quantitative method in measuring WMC. METHODS: The authors examined 220 magnetic resonance images from stroke-free patients with traditional risk factors for atherosclerosis and middle cerebral artery stenosis who were participants in a clinical trial requiring MRI examination. The severity of WMC was graded from 0 (no WMC) to 3 (severe WMC). For the quantitative assessment of WMC, the volume of WMC were measured with a computer-aided, automated segmentation method. The interobserver variability was also determined. RESULTS: The mean volumes were significantly different among the different groups, which were scored 1, 2, and 3 (1324.59, 6475.48, and 25,440.05 mm3, respectively; 1-way analysis of variance, P < .001). Interobserver variability for grading WMC was good in different locations of the brain. Excellent results were found in the frontal lobe (kappa = 0.829) and the parietal-occipital lobe (kappa = 0.646), whereas poor results were found in the basal ganglia (kappa = 0.391). There was perfect agreement between the 2 observers in 89.1% for the frontal lobe and 77.0% for the parietal-occipital lobe. CONCLUSIONS: The results suggest that this simple visual rating scale is a valid and reliable method for grading WMC in the lobar region but not in the basal ganglion.

Brain↗
PubMed2002

Mechanisms of acute cerebral infarctions in patients with middle cerebral artery stenosis: a diffusion-weighted imaging and microemboli monitoring study.

Although most therapeutic efforts and experimental stroke models focus on the concept of complete occlusion of the middle cerebral artery as a result of embolism from the carotid artery or cardiac chamber, relatively little is known about the stroke mechanism of intrinsic middle cerebral artery stenosis. Differences in stroke pathophysiology may require different strategies for prevention and treatment. We prospectively studied 30 consecutive acute ischemic stroke patients with middle cerebral artery stenosis detected by transcranial Doppler and magnetic resonance angiography. Patients underwent microembolic signal monitoring by transcranial Doppler and diffusion-weighted magnetic resonance imaging. Characteristics of acute infarct on diffusion-weighted magnetic resonance imaging were categorized according to the number (single or multiple infarcts) and the pattern of cerebral infarcts (cortical, border zone, or perforating artery territory infarcts). The data of microembolic signals and diffusion-weighted magnetic resonance imaging were assessed blindly and independently by separate observers. Diffusion-weighted magnetic resonance imaging showed that 15 patients (50%) had single acute cerebral infarcts and 15 patients had multiple acute cerebral infarcts. Among patients with multiple acute infarcts, unilateral, deep, chainlike border zone infarcts were the most common pattern (11 patients, 73%), and for single infarcts, penetrating artery infarcts were the most common (10 patients, 67%). Microembolic signals were detected in 10 patients (33%). The median number of microembolic signals per 30 minutes was 15 (range, 3-102). Microembolic signals were found in 9 patients with multiple infarcts and in 1 patient with a single infarct (p = 0.002, chi(2)). The number of microembolic signals predicted the number of acute infarcts on diffusion-weighted magnetic resonance imaging (linear regression, adjusted R(2) =0.475, p < 0.001). Common stroke mechanisms in patients with middle cerebral artery stenosis are the occlusion of a single penetrating artery to produce a small subcortical lacuna-like infarct and an artery-to-artery embolism with impaired clearance of emboli that produces multiple small cerebral infarcts, especially along the border zone region.

Acute Disease↗
PubMed2002

Progression of middle cerebral artery occlusive disease and its relationship with further vascular events after stroke.

BACKGROUND: Serial changes of flow velocities of transcranial Doppler ultrasound (TCD) in symptomatic middle cerebral artery (MCA) occlusive disease may be related to the occurrence of further vascular events, but prospective data are lacking. METHODS: We conducted a prospective study on patients with cerebral ischemia who were hospitalized with symptomatic MCA stenosis or occlusion. We repeated TCD examinations 6 months after the initial examinations and recorded any stroke or coronary events during this period. The changes of MCA flow velocities were categorized as normalized artery, stable artery, and progressed artery, which were determined according to the changes of MCA velocities at 6 months. RESULTS: We studied 143 consecutive patients who had relevant MCA occlusive diseases (107 with stenosis and 36 with occlusion). At 6 months, the velocities in the MCA returned to normal in 42 patients (29%), they were stable in 80 patients (62%), and they progressed in 13 patients (9%). The number of clinical events varied significantly among the 3 groups: there were 2 patients (4.8%) with clinical events in the normal group, 11 patients (12.5%) with clinical events in the stable group, and 5 patients (38.5%) with clinical events in the progressed group (P=0.004). The 18 recurrent events included 10 recurrent strokes, 5 transient ischemic attacks, and 3 acute coronary syndromes. CONCLUSIONS: Progression of MCA occlusive diseases is associated with an increased risk of vascular events. Further studies are required to establish the value of serial TCD examinations in predicting future clinical events.

Aged↗
PubMed2002

Optimal values of flow velocity on transcranial Doppler in grading middle cerebral artery stenosis in comparison with magnetic resonance angiography.

BACKGROUND AND PURPOSE: To investigate the optimal values of flow velocity on transcranial Doppler (TCD) in grading the severity of middle cerebral artery (MCA) stenosis in comparison with magnetic resonance angiography (MRA). METHODS: Both TCD and MRA examinations were performed on 148 asymptomatic patients. The peak flow velocities of each MCA were recorded. Severity of MCA stenosis on MRA was classified as normal-mild (< 50% lumen diameter reduction), moderate (50%-75%), and severe-void (> 75% and void of flow signal). RESULTS: Among 296 MCAs evaluated, normal-mild stenosis was found in 75 (25%), moderate stenosis in 112 (38%), and severe stenosis in 109 (37%). The mean of systolic velocity (Vs) of MCA differed significantly among these three groups: mean Vs = 121.83 +/- 22.52 cm/s in the normal-mild group; 155.96 +/- 21.62 cm/s for the moderate group; and 199.39 +/- 43.86 cm/s for the severe group (P < .001). The optimal cutoff velocity for detection of MCA (> 50%) stenosis was found at Vs > 140 cm/s on TCD (area under the ROC curve is 0.87, P < 0.001). The best cutoff points for grading severity of on TCD were 140 cm/s and 180 cm/s. CONCLUSION: TCD enables grading of the severity of MCA stenosis according to the flow velocity. This method provides a noninvasive and reliable method for grading MCA stenosis and allows longitudinal monitoring of the relationship between clinical outcome and hemodynamic change.

Blood Flow Velocity↗