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R T Cheung

Publications and source records attributed to R T Cheung.

At least 55 records · Page 3Linked to original sources
PubMed1998

Prevalence of extracranial carotid and vertebral artery disease in Chinese patients with coronary artery disease.

BACKGROUND AND PURPOSE: Chinese have been reported to have an extremely low prevalence rate of carotid and vertebral artery disease in comparison with whites. Previous studies, however, have been limited to general hospital stroke admission or postmortem series and were prone to selection bias. Extracranial cerebrovascular disease (ECCVD) is associated with coronary artery disease (CAD) in whites. Data associating ECCVD with CAD in Chinese patients are not available. METHODS: We studied 153 consecutive Chinese patients with angiographically documented CAD. Duplex ultrasonography was performed to identify any underlying extracranial carotid and vertebral artery disease. Patient demographics; vascular risk factors; history of myocardial infarction, transient ischemic attack (TIA) or stroke; concomitant peripheral vascular disease (PVD); degree of left ventricular dysfunction; and extent and severity of CAD were also noted and analyzed. RESULTS: Significant (> or = 50%) stenosis of one or more of the extracranial cerebral arteries was found in 32 patients (21%). The internal and external carotid arteries were involved in 17 of 153 patients (11%) and 19 of 153 patients (12%), respectively. The vertebral artery was involved in 9 of 153 patients (6%) and the common carotid artery in 3 of 153 (2%). Diabetes mellitus, hypertension, a history of TIA or stroke, and PVD were significantly associated with the presence of ECCVD. CONCLUSIONS: Significant ECCVD is not uncommon in Chinese patients with CAD, and the prevalence is comparable with that reported in white populations. Patients with a history of diabetes, hypertension, TIA, stroke, and PVD are more likely to have concomitant ECCVD.

Aged↗
PubMed1998

Tuberculosis meningitis in Hong Kong: experience in a regional hospital.

Tuberculous meningitis (TBM) remains common in Hong Kong. From January 1996 to June 1997, 11 adult patients with TBM presented to Queen Mary Hospital, a regional hospital in Hong Kong. The annual incidence of TBM was estimated at 1.8 per 100,000 population. Nine patients were local Chinese, and only one patient had the acquired immune-deficiency syndrome (AIDS). In contrast to the classical presentation as a chronic indolent disease, our patients presented acutely: the mean duration from onset of symptoms to presentation was 4.8 days (range 0-10). The most common presenting symptoms were headache (64%), fever (46%), or both (36%), with focal deficits occurring in 64% of patients. Cerebrospinal fluid (CSF) culture and polymerase chain reaction (PCR) were positive in 30% and 29% of cases. Mean CSF cell count, protein and glucose levels were 340 x 10(6)/L, 267 mg/dL, and 2.3 mmol/L, respectively. Extra-neural tuberculosis occurred in 46% of cases. All patients survived and responded to treatment. Drug-induced hepatotoxicity was common; 64% of patients developed biochemical hepatitis.

Adult↗
PubMed1997

Colchicine affects cortical and amygdalar neurochemical changes differentially after middle cerebral artery occlusion in rats.

Recently, we have shown increases in the immunoreactivity for neuropeptide Y and tyrosine hydroxylase in the insular cortex surrounding the focal infarction after middle cerebral artery occlusion. In addition, the immunoreactivity for neuropeptide Y, leucine-enkephalin, dynorphin, and neurotensin increased ipsilaterally in the amygdala. Increases in immunoreactivity were observed in nerve terminals and fibers; changes in the neuropeptides were maximal 3 days after stroke. Local excitotoxic injury of the insular cortex also elicited similar neuropeptide changes unilaterally in the same regions. In this study, immunohistochemistry was used following intracerebroventricular injection of colchicine and stroke to determine whether blockade of axonal transport would prevent these neurochemical changes. These experiments would also locate the putative cellular origins of the neurochemicals involved. Control rats received either colchicine injection or middle cerebral artery occlusion alone. Injection of colchicine enhanced the periinfarct increase in neuropeptide Y but did not alter the increase in tyrosine hydroxylase. The neuropeptide Y increase was observed in local cortical neurons. Colchicine prevented the increases in immunoreactivity for the neuropeptides in the amygdala on the side of stroke, although there were small perikarya that showed immunoreactivity for these neuropeptides within the amygdala on both sides. We conclude that local cortical neurons are responsible for the increase in neuropeptide Y in the periinfarct region, that the cortical increase in tyrosine hydroxylase is not dependent on fast axonal transport, and that axonal transport of signals from the insular cortex to the amygdala is critical in mediating the amygdalar neuropeptide changes seen after stroke.

Amygdala↗
PubMed1997

Cardiovascular response to stress after middle cerebral artery occlusion in rats.

Previously, we have shown cardiovascular and autonomic disturbances in male Wistar rats following middle cerebral artery occlusion (MCAO). Using this model, neurochemical changes, that were maximal at 3-5 days and subsiding by day 10, were observed unilaterally in the insular cortex and amygdala. The amygdalar neurochemical changes may be related to the stroke-induced cardiovascular disturbances, since the amygdala is critical in mediating the cardiovascular responses to stress. We examined the cardiovascular responses to intermittent and continuous noise and air-jet stimulation in male Wistar rats on days 2-10 after right-sided MCAO or sham MCAO. Compared to the sham MCAO rats, intermittent noise elicited significant tachycardiac responses on days 5 and 7 after stroke. Air-jet stimulation also elicited a significant tachycardic response on day 5, whereas continuous noise produced significant tachycardiac and pressor responses at days 5 and 7, respectively, in the MCAO rats compared to the control rats. Analyses on the heart rate variability using fast Fourier transformation revealed significant increases in the normalized mid-frequency spectral power on day 7 for intermittent noise and air-jet stimulation, suggesting increases in the sympathetic activity. These results indicate a time-course of exaggerated cardiovascular responses to stress and suggest a state of susceptibility to cardiac perturbations in rats following stroke.

Amygdala↗
PubMed1997

Neurological complications of heart disease.

Focal deficits, seizures and epilepsy, altered consciousness, and disturbed behaviours can complicate heart diseases and their medical treatment as well as cardiological procedures and cardiac surgery. Neurological complications of common cardiac conditions are discussed. These cardiac conditions are acute myocardial infarction and ischaemic heart disease, atrial fibrillation and cardiac arrhythmias, congestive heart failure, valvular heart diseases, infective endocarditis, congenital heart disease, invasive cardiological procedures and cardiac surgery. As transient ischaemic attack, stroke, seizures and epilepsy are the most common neurological complications, their management is also reviewed. Precautions should be taken to prevent neurological complications of heart disease. Regular surveillance for these complications would allow early diagnosis and initiation of appropriate management.

Animals↗
PubMed1996

Motor neuron disease in Hong Kong Chinese: epidemiology and clinical picture.

This study documents the clinical features, incidence and prevalence of motor neuron disease (MND) in Hong Kong Chinese. Patients with MND who were alive between 1989 and 1992 were recruited by retrieval of medical records from the four major hospitals in Hong Kong, and by referral of neurologists, neurosurgeons and medical consultants. Mortality statistics was provided by the Census and Statistics Department. A total of 84 cases were identified with a male preponderance of 1.98:1. The average annual period incidence was 0.31/100,000 and the point prevalence on December 31, 1992, was 0.95/100,000. The mean age at onset was 55.5 years (range 19-81) with a peak observed from 55 to 65 years. The clinical features are similar to other reported series of MND. The incidence and mortality of MND in Hong Kong are therefore lower than the worldwide figures of 2.0/100,000 and 1.5/ 100,000, respectively.

Adult↗
PubMed1995

Neuropeptide changes following excitotoxic lesion of the insular cortex in rats.

Following middle cerebral artery occlusion in Wistar rats, the immunoreactivity of neuropeptide Y increased ipsilaterally in the insular cortex and basolateral nucleus of the amygdala. In addition, the immunoreactivity of leucine-enkephalin, dynorphin, and neurotensin increased in the ipsilateral central nucleus of the amygdala. The amygdalar neurochemical changes are likely the result of damage to the insular cortex, although other cortical areas were also affected by the ischemia. To investigate whether damage to the insular cortex is essential in eliciting these changes, a localized lesion of the right or left insular cortex was produced by microinjection of D,L-homocysteic acid. Control animals received injections of vehicle into the right or left insular cortex or D,L-homocysteic acid into the right primary somatosensory cortex. Neurochemical changes were examined immunohistochemically with the peroxidase-antiperoxidase reaction 5 days after the injection. The immunoreactivity of neuropeptide Y increased locally after excitotoxic damage to the insular cortex or primary somatosensory cortex. The amygdalar neurochemical changes, including neuropeptide Y increase in the basolateral nucleus and leucine-enkephalin, dynorphin, and neurotensin increase in the central nucleus, were seen only when the ipsilateral insular cortex was lesioned. These neurochemical changes were similar to those seen 5 days after middle cerebral artery occlusion. Our findings indicate that damage to the insular cortex is essential in eliciting the neurochemical changes in the ipsilateral amygdala. In addition, the change in neuropeptide Y in the cortex appears to be a local reaction occurring irrespective of location of the lesion and glutamate receptor activation may be involved.

Amygdala↗
PubMed1995

Time-course of neuropeptide changes in peri-ischemic zone and amygdala following focal ischemia in rats.

Previously, using a middle cerebral artery occlusion model in Wistar rat, we showed autonomic disturbances similar to those seen clinically and observed striking neurochemical changes in cortical and subcortical sites at 5 days following stroke. The neurochemical changes may account for functional recovery and/or autonomic disturbances after focal ischemia. To understand the possible mechanisms and to facilitate future studies, it is necessary to define the time-courses of these changes. Using immunohistochemical staining with the peroxidase-antiperoxidase reaction, the changes in several neuropeptides over the peri-ischemic region and the ipsilateral central and basolateral nucleus of the amygdala were investigated at different times after middle cerebral artery occlusion. In the experimental group, neuropeptide Y immunoreactivity appeared to increase by 6 hours in the peri-ischemic region. Using image analysis to quantify the staining intensity, the change became statistically significant at 1 day, peaked around 3 days, and subsided at 10 days. There was a delayed increase in neuropeptide Y in the ipsilateral basolateral nucleus of the amygdala with a peak around 3 days. Immunoreactive staining for leucine-enkephalin, dynorphin, and neurotensin demonstrated an increase that was localized to the ipsilateral central nucleus of the amygdala with a peak around 3 days and a return to baseline levels by 10 days. The results support a specific time-course for each of the neuropeptides studied and indicate that a survival time of 3 days after focal ischemia is the critical period for examining the relationship between neuropeptide responses and neuronal or functional recovery.

Amygdala↗
PubMed1995

Neurochemical changes following occlusion of the middle cerebral artery in rats.

We have developed a stroke model involving middle cerebral artery occlusion in the rat which elicits changes in cardiac and autonomic variables that are similar to those observed clinically. It is likely that these neurogenic autonomic responses are mediated by changes in neurotransmitter systems subsequent to the stroke. This possibility was investigated by examining changes in immunohistochemical staining for tyrosine hydroxylase, neuropeptide Y, leu-enkephalin, neurotoxins and dynorphin following middle cerebral artery occlusion in the rat. Computerized image analysis was used to provide semi-quantitative measurements of the changes. The ischemic region was centered primarily in the insular cortex. The results indicate that there are significant increases in immunostaining for tyrosine hydroxylase and neuropeptide Y in the insular cortex within the peri-infarct region. Neuropeptide Y staining was also significantly increased in the basolateral nucleus of the amygdala, ipsilateral to the middle cerebral artery occlusion, which did not appear to be included in the infarct. Leu-enkephalin, neurotensin and dynorphin staining was significantly elevated in the central nucleus of the amygdala ipsilateral to the occlusion of the middle cerebral artery. These neurochemical changes are discussed as possible mechanisms mediating the cardiac and autonomic consequences of stroke or as part of a process to provide neuro-protection following focal cerebral ischemia.

Amygdala↗
PubMed1994

Management of tetanus: a review of 18 cases.

Eighteen patients with generalized tetanus seen during an 8-year period in three regional hospitals in Hong Kong are reviewed. Eighty-nine per cent of the patients were intravenous heroin addicts who developed a severe type of generalized tetanus with autonomic dysfunction. Pain or stiffness of the neck or back was the commonest presenting symptom, followed by trismus and dysphagia. Most of the patients developed muscle spasms within 24 h of the onset of presenting symptoms. Early ventilatory support and tracheostomy, together with intensive nursing care, were the mainstay of the treatment. Pulmonary and gastrointestinal complications were common during the course of illness and treatment of autonomic dysfunction was often unsatisfactory. The case fatality rate was 25% among the heroin addicts, but full recovery was the usual outcome for those who survived. The simultaneous administration of intrathecal tetanus immunoglobulin tends to reduce mortality.

Adult↗
PubMed1994

Primary cerebral abscess due to Nocardia asteroides presenting as stroke.

Nocardial cerebral abscess, an uncommon condition, is usually secondary to a septic focus elsewhere in the body. We report a 44-year-old Chinese male patient who had primary nocardial cerebral abscesses due to Nocardia asteroides which presented with stroke-like episodes. He improved spontaneously between these episodes. The diagnosis was reached only after a contrast CT brain study and microbiological examination of specimens obtained during craniotomy. An early contrast CT study is important in avoiding any delay in diagnosis and treatment of this serious condition.

Abscess↗
PubMed1993

Treatment of acute cortical infarct with intravenous glycerol. A double-blind, placebo-controlled randomized trial.

BACKGROUND AND PURPOSE: This clinical trial investigates the effectiveness of intravenous glycerol therapy in patients with acute cortical infarction in whom intracerebral hemorrhage was rigorously excluded. METHODS: Within 48 hours of symptoms from their first ischemic stroke, 113 hospital inpatients were randomized into the trial, provided that hemorrhage was excluded by computed tomography and informed consent was obtained. Patients were stratified into alert, semicoma, and coma groups using the Glasgow Coma Scale. Treatment was allocated according to a double-blind, randomized protocol; 56 patients received 500 mL of 10% glycerol in saline over 4 hours on 6 consecutive days, and 57 patients received corresponding placebo treatment with saline. Using a variety of objective scoring systems, patient follow-up was up to 6 months. RESULTS: Corresponding measures of outcome in the glycerol and placebo groups were similar. At 6 months, respective mortality rates were 17 of 56 and 16 of 57, and mean +/- SD improvements in scores were 9.98 +/- 14.40 vs 10.51 +/- 12.68 (long-term), 1.12 +/- 7.20 vs 1.57 +/- 6.30 (prognostic), -1.94 +/- 5.53 vs -2.06 +/- 5.34 (Glasgow Coma Scale), and 21.72 +/- 23.40 vs 11.94 +/- 18.10 (Barthel Index rating in survivors). Hemolysis (generally subclinical) was the only adverse effect. CONCLUSIONS: There was no clinically or statistically significant difference in outcome between the groups; a trend toward greater functional recovery among survivors was evident after treatment with glycerol.

Acute Disease↗