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Biomedical subjects

F L Chan

Publications and source records attributed to F L Chan.

At least 19 recordsLinked to original sources
PubMed1995

Low-molecular-weight heparin for the treatment of acute ischemic stroke.

BACKGROUND: Despite doubts about their efficacy and concern about their safety, antithrombotic agents are often used to treat acute ischemic stroke. Recent experience in patients with other thromboembolic disorders suggests that low-molecular-weight heparin, which requires only subcutaneous administration once or twice daily, may be more effective and safer than standard (unfractionated) heparin. METHODS: We conducted a randomized, double-blind, placebo-controlled trial comparing two dosages of low-molecular-weight heparin with placebo in the treatment of ischemic stroke. Patients were randomly assigned within 48 hours of the onset of symptoms to receive high-dose nadroparin (4100 anti-factor Xa IU twice daily), low-dose nadroparin (4100 IU once daily), or placebo subcutaneously for 10 days. The primary measure of outcome was death or dependency regarding activities of daily living six months after randomization. Secondary outcomes were death, hemorrhagic transformation of the infarction, and other complications at 10 days, and death or dependency at 3 months. RESULTS: A total of 2750 patients were screened for the study. Among 312 patients randomized, 306 had outcomes that were analyzed at six months. Forty-five patients (45 percent) in the high-dose group, 53 patients (52 percent) in the low-dose group, and 68 patients (65 percent) in the placebo group died or became dependent. There was a significant dose-dependent effect among the three study groups in favor of low-molecular-weight heparin (P = 0.005 by the chi-square test for trend). No significant differences among the groups in the occurrence of secondary outcomes were observed at 10 days. CONCLUSIONS: For patients with ischemic stroke treated within 48 hours of the onset of symptoms, low-molecular-weight heparin was effective in improving outcomes at six months.

Activities of Daily Living↗
PubMed1995

Direct coronal computed tomography of the upper cervical spine.

STUDY DESIGN: The technique of obtaining direct coronal computed tomography images of the upper cervical spine is described. OBJECTIVES: To show the usefulness of this technique in demonstrating upper cervical spine lesions and to show that orbital (lens) radiation dosage is minimal compared with conventional tomography. SUMMARY OF BACKGROUND DATA: Conventional tomography is used routinely for assessment of the odontoid peg and upper cervical spine lesions. Direct coronal computed tomography for imaging the cervical spine has not been previously described. METHODS: Using a removable head support device, direct coronal images are obtained using a computed tomography scanner. The gantry tilt is adjusted from the scanogram. Direct comparison of orbital radiation dosages between computed tomography and conventional tomography is made from placement of thermoluminescent dosemeter chips onto a phantom. RESULTS: Direct coronal computed tomography provide superior demonstration of skeletal features in the upper cervical spine. Orbital radiation dose is negligible compared with conventional tomography. CONCLUSION: This technique may replace conventional tomography in assessing of stable upper cervical spine lesions.

Cervical Vertebrae↗
PubMed1995

Magnetic resonance imaging of cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis is a rare familial sterol storage disease with accumulation of cholestanol and cholesterol particularly in xanthomas, bile and brain. Magnetic resonance imaging is a useful modality for imaging the affected tissues. It contributes to the evaluation and management of the disease.

Brain↗
PubMed1994

Parapharyngeal teratoma in the newborn.

A parapharyngeal teratoma in a newborn was the cause of acute respiratory distress, which was relieved by tracheostomy. Subsequent investigations by soft tissue x-rays of the neck, computed tomography, and examination under anesthesia defined the anatomic location of the tumor, its extent, and its likely nature. The tumor was removed completely by the transcervical approach. Mandibulotomy was not required. Histological examination showed the presence of a large amount of mature brain tissue, a moderate amount of collagenous fibers and smooth muscle cells, and a minute amount of cartilage and epithelial structures. The postoperative course was satisfactory. No recurrence was seen 6 years after surgery. The computed tomography scan was found to be the most useful investigative method. To the authors' knowledge, this is the first comprehensive report of a teratoma occupying the parapharyngeal space in a newborn.

Female↗
PubMed1994

Pancreatic pleural effusion: an indication for emergency distal pancreatectomy and Roux-en-Y pancreatico-jejunostomy.

A previously healthy 2-year-old boy was admitted because of shortness of breath, cough, and fever; there was minimal abdominal pain. He had recurrent right, followed by left pleural effusions, which contained markedly elevated amylase levels and high protein content. The pleural fluid amylase levels were disproportionately higher than the serum amylase levels. His abdominal signs were minimal. Surgical exploration showed a disruption of the proximal pancreatic duct. Distal pancreatectomy and Roux-en-Y pancreatico-jejunostomy were performed. After a complicated postoperative course he was discharged well and has remained so for more than 2 years.

Anastomosis, Roux-en-Y↗
PubMed1992

Aldosteronoma coexisting with renal artery stenosis in secondary hypertension.

A case of secondary hypertension due to an aldosteronoma coexisting with renal artery stenosis is reported. Tumor resection resulted in an immediate but short-lived clinical relief. Follow-up aortography revealed progressive arterial stenosis and infrarenal aortic occlusion. Differential renal venous renin and renal scintigraphy suggested renovascular hypertension. It is necessary to search for a second curable lesion if hypertension remains uncontrollable after surgical correction of an apparent cause.

Adenoma↗
PubMed1992

Case report: localization of occult insulinoma by intra-arterial stimulation with calcium and venous sampling technique.

Hypoglycaemia as a result of insulin secreting tumours can be treated effectively by surgery. However pre-operative localization is desirable as the majority of these tumours are small and in 20% of the cases may be multiple. We describe a 1 cm insulinoma being localized pre-operatively by selective arterial stimulation with calcium and venous sampling for insulin. This technique is sensitive and relatively non-invasive. We believe that it is potentially very valuable in pre-operative localization of occult insulinomas.

Adult↗
PubMed1992

Computed tomography of paranasopharyngeal spaces: normal variations and criteria for tumour extension.

In 137 normal CT scans of the nasopharynx, the parapharyngeal spaces at the nasopharynx level were asymmetrical in 30%. Their difference in width and distance from the midline was greater than 1 mm in 51% and 44% respectively. Fat was absent in the interpterygoid fascia in 20%, in the alar fascia in 28%, in the prevertebral space in 35%, and in the retropharyngeal space in 99% of patients. Assessment of tumour extension to the paranasopharyngeal space usually relies on symmetry and fascial fat planes. As either feature may not be present in the normal person, the relation of the tumour to two lines representing two fascial planes is proposed as a complementary method for the evaluation of tumour extension.

Adipose Tissue↗
PubMed1992

Infratemporal pneumatocele arising from maxillary sinus.

Pneumatocele of the infratemporal fossa caused by herniation of air through a break in the wall of the aerated maxillary sinus is rare. Two cases are reported: one arising from a maxillary pneumocele with a defect in the wall of the zygomatic recess and one associated with maxillary radionecrosis with pathological fracture complicated by infection. Computed tomography can clearly demonstrate the extent of the pneumatocele, and can show the maxillary pathology and the causative bony defect in the sinus. Treatment depends on the clinical conditions of the patient, the pathology and the size of the bony defect.

Adult↗
PubMed1992

Post-transplant erythrocytosis: role of erythropoietin and male sex hormones.

Seventeen patients with post-renal transplant erythrocytosis and 17 non-erythrocytotic controls, matched in age, sex, serum creatinine and source of donor kidney, were studied to determine the role of erythropoietin, male sex hormones (testosterone, FSH, LH), and various patient risk factors in post-transplant erythrocytosis. Serum erythropoietin was significantly greater in erythrocytotic patients (35.6 +/- 5.7 mU/ml) than non-erythrocytotic patients (18.8 +/- 2.6 mU/ml) (P less than 0.05) and normal subjects (22.5 +/- 0.95 mU/ml) P less than 0.05). Serum testosterone was similar between the male study (13.2 +/- 6.2 nmol/l) and control (13.1 +/- 6.0 nmol/l) patients. This might be due to the greater basal LH in the male control subjects (13.9 +/- 11.7 IU/l versus 8.0 +/- 3.3 IU/l in erythrocytotic males, P = 0.084). Basal FSH in the male controls was greater than that in the study group (13.7 +/- 14 IU/l versus 6.8 +/- 2.9 IU/l, P = 0.067). Among the demographic risk factors, only the smoking history was important. There were more smokers among the erythrocytotic patients than controls (P = 0.051).

Adult↗
PubMed1992

A comparative study of computed tomographic and plain radiographic methods to measure vertebral rotation in adolescent idiopathic scoliosis.

A comparative analysis of two methods of measuring vertebral rotation in adolescent idiopathic scoliosis is reported in this article. Nash and Moe's pedicle shift method (using plain anteroposterior radiographs) is compared with a new method using computed tomographic scans. The computed tomographic scans of the whole length of the major curve and the scout films obtained from seventeen girls aged 12.5-14 years were measured for rotation of each vertebra of the curve (total number of vertebrae measured by two methods = 173). This study has three interesting new findings: 1) Those vertebrae with Nash & Moe grade 0 had up to 11 degrees of vertebral rotation when measured using the computed tomographic method. Therefore, Nash & Moe's grade '0' is not a neutrally rotated vertebra; 2) For Nash & Moe grade 1 and 2, the computed tomographic method revealed statistically significantly greater rotation for lumbar vertebrae than thoracic vertebrae. There was a similar pattern for Nash & Moe grade 0 but these differences were not statistically significant; and 3) Simple formulae are reported to convert Nash & Moe's grades into angle of vertebral rotation as obtained by CT method separately for thoracic and lumbar vertebrae.

Adolescent↗
PubMed1992

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

BACKGROUND AND PURPOSE: Hitherto, treatment of acute cerebral hemorrhage with intravenous glycerol has not been evaluated in rigorous clinical studies with sufficient patient numbers. METHODS: We undertook a double-blind, stratified and randomized, placebo-controlled clinical trial. Only patients with a first stroke admitted to the hospital within 24 hours after onset of symptoms were recruited, provided computed tomography confirmed hemorrhage and informed consent was obtained. After stratification into alert, semicoma, and coma subgroups using the Glasgow Coma Scale, 107 patients received active treatment (500 ml of 10% glycerol in saline by intravenous infusion over 4 hours on 6 consecutive days) and 109 were given corresponding saline treatment. Using a variety of objective scoring systems, patients were followed up for up to 6 months. RESULTS: At follow-up, all measures of outcome in the treated and control groups were very similar. At 6 months, respective mortality rates were 37 of 107 and 33 of 109. Corresponding mean +/- SD improvements in Scandinavian Stroke Study Group scores were 8.35 +/- 16.9 versus 11.55 +/- 15.6 (long-term) and 0.64 +/- 7.3 versus 2.40 +/- 6.9 (prognostic), and improvements in the Barthel Index ratings were 10.72 +/- 24.7 versus 13.95 +/- 23.3, respectively. Glasgow Coma Scale score improvements in the survivors were 0.81 +/- 1.5 and 1.16 +/- 1.7 in the treated and control groups, respectively. Hemolysis (generally subclinical) was the only adverse effect of glycerol noted. CONCLUSIONS: In the absence of any clinically or statistically significant difference in outcome between the treated and control groups, this trial provides no justification for glycerol therapy following acute cerebral hemorrhage.

Acute Disease↗
PubMed1992

Localization of heparan sulfate proteoglycan in basement membrane by side chain staining with cuprolinic blue as compared with core protein labeling with immunogold.

We localized heparan sulfate proteoglycan (HSPG) in the basement membranes of ciliary epithelium and plantar epidermis, using Cuprolinic blue to stain its side chains and an immunogold procedure to detect its core protein. In accord with most of the literature, staining with Cuprolinic blue in glutaraldehyde fixative yielded three to five times as many reaction products along the two surfaces than along the center of the lamina densa, whereas immunogold labeling for the core protein after formaldehyde fixation yielded about twice as many gold particles over the center than along the surfaces of the lamina densa. It therefore appeared that HSPG side chains predominated outside, and the core protein within, the lamina densa. To find out whether the discrepancy was true or was an artifact caused by differences in processing, we attempted to combine the two approaches on the same material. This was found possible when Cuprolinic blue was used in formaldehyde fixative, embedding was in LR White, and immunogold labeling was performed on thin sections as usual. Under these conditions, both Cuprolinic blue reaction products and immunogold particles predominated over the lamina densa in the two basement membranes under study. Moreover, evidence was present that reaction products and immunogold particles either overlapped each other or were closely associated. The lens capsule (a thick basement membrane) also showed their co-localization. The discrepancy initially observed between side chains and core protein location was attributed to differences in processing, since Cuprolinic blue staining had been carried out in the course of glutaraldehyde fixation whereas immunogold labeling was done after formaldehyde fixation. The results lead to two conclusions. First, processing differences may alter the localization of HSPG and possibly other proteoglycans. Second, both HSPG side chains and core protein are localized in the same sites within basement membrane.

Animals↗
PubMed1991

Cranial nerve involvement and base of the skull erosion in nasopharyngeal carcinoma.

In a prospective study of 262 consecutive patients with nasopharyngeal carcinoma (NPC), using computed tomography (CT) as their baseline evaluation, erosion of the base of the skull and intracranial extension into the middle cranial fossa were found in 31.3% and 12.2% of patients, respectively. Thirty-four of these patients had cranial nerve involvement at presentation; 30 of them had involvement of one or more of the third to sixth cranial nerves. Most cases of intracranial extension of tumor were accompanied by erosion of the base of the skull, but the reverse was not true. All patients with cranial nerve palsy involving the third to sixth cranial nerves had associated erosion of the ipsilateral base of the skull. The CT evaluation of patients with cranial nerve involvement who are believed to harbor NPC should include thin cuts of the base of the skull for detection of subtle bone erosion. This may be the only clue to the presence of a small NPC. The prognostic significance of cranial nerve involvement, base of the skull erosion, and intracranial extension of the tumor on the survival of the group of 84 patients who had T4 tumors was evaluated with regression analysis using the Cox model. Only cranial nerve involvement was found to be a significant factor influencing survival.

Cranial Nerve Neoplasms↗
PubMed1991

Biliary cystadenoma and cystadenocarcinoma: some unusual features.

Biliary cystadenoma and cystadenocarcinoma are rare tumours which have a good prognosis after complete surgical removal. Correct pre-operative diagnosis depends on the imaging characteristics of the tumours. We have observed some unusual features including multifocal tumours with attachment to other abdominal organs, tumour presenting as cholangitic abscess, and distant metastasis after apparently complete resection by hemihepatectomy.

Adult↗