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Biomedical subjects

L L Leong

Publications and source records attributed to L L Leong.

At least 19 recordsLinked to original sources
PubMed2001

Ultrasonographic measurement of subarachnoid space in normal infants and children.

This study was undertaken to evaluate the sonographic measurement of subarachnoid spaces in normal children and its relationship with age and to define a normal range in a Chinese population and to differentiate normal variant findings from pathologic dilatation. The subarachnoid spaces in 278 normal term neonates, infants, and children were studied with real-time ultrasound using a 7.5-MHz vector transducer. The craniocortical width, sinocortical width, and interhemispheric width were measured in the coronal plane at the level of the foramen of Monro, on either side of the hemispheres. Correlation of sonographic measurements with age was made. The mean widths were plotted against age. A correlation with age was found in all three spaces, with an increasing trend with age until 28 weeks of gestation. Thereafter, a decreasing trend was noted. The normal upper limit of subarachnoid spaces for children is proposed to be the values on the ninety-fifth percentile of the regression curve. Correlation of measurement with age must be considered to decide whether an increase in subarachnoid space is pathologic or not.

Cephalometry↗
PubMed1999

A case-controlled MRI/MRA study of neurovascular contact in hemifacial spasm.

BACKGROUND: Neurovascular contact (NVC) with the root exit zone (REZ) of the ipsilateral facial nerve is associated with hemifacial spasm (HFS), but unresolved issues remain. OBJECTIVES: To 1) determine the frequency of symptomatic and nonsymptomatic NVC, 2) determine the features of NVC associated with HFS, and 3) correlate severity of HFS to these features. METHODS: Two independent, blinded, prospective assessments of high-resolution MR and MR angiography (MRA) images were performed on Chinese cases (HFS: n = 44; age-matched control subjects: n = 20). RESULTS: Over 88% of 44 symptomatic sides in patients with HFS had NVC of the ipsilateral facial nerve. At least 80% of symptomatic sides involved NVC at the anterior aspect of the REZ [REZ(ant.)]. Although NVC was observed in approximately half of nonsymptomatic sides, at least 70% of them were not at REZ(ant.). NVC at the cisternal and intracanalicular portions of the facial nerve were not associated with HFS. Half of our patients with HFS had bilateral NVC, but none had bilateral symptoms. Most of our MR/MRA images showed that the size and position of the arterial branches of the vertebrobasilar system were markedly asymmetric. Of patients with bilateral NVC, over 83% had asymmetric NVC sites. The anterior inferior cerebellar artery was the most common vessel involved in NVC, but was not significantly associated with HFS. Most of the NVC involved one vessel at one contact point with no indentation. The development of HFS was significantly associated with nerve indentation in NVC. The development and severity of HFS were not associated with multiple contact points in NVC. No significant interobserver variability existed between the blinded assessments. CONCLUSIONS: MRI/MR angiography are accurate, fast, and safe in characterizing neurovascular contact (NVC) at the brainstem. The site of NVC and ipsilateral facial nerve indentation in NVC are significant determinants for the development of hemifacial spasm (HFS). The lack of bilateral NVC at the anterior aspect of the root exit zone of the facial nerve could explain in part the lack of bilateral symptoms. The development and severity of HFS are not associated with a specific blood vessel or multiple contact points in NVC.

Adult↗
PubMed1999

Ultrasound contrast agent Levovist in colour Doppler sonography of hepatocellular carcinoma in Chinese patients.

In a phase IIIb clinical trial of the ultrasound contrast agent Levovist (Schering AG, Berlin, Germany), the role of Levovist in the management of patients with clinically suspected hepatocellular carcinoma (HCC) was evaluated and its efficacy was assessed. The assessment included the duration of diagnostically usable Doppler signal enhancement, and safety and tolerance of intravenous administration. All patients with clinically suspected hepatocellular carcinoma were referred for Doppler sonographic examination over a 5-month period and lesions with absent or suboptimal Doppler signals were included in the trial. A total of 300 mg/mL in concentration (8.5 mL) of Levovist was administered through a peripheral vein while Doppler signal intensity in the lesion, based on a visual score, was recorded. Blood pressure and pulse were recorded before and after injection. Thirty-eight patients were examined, of which 29 were included in the trial. The lesions were subsequently proven histologically to be 19 HCC, one cholangiocarcinoma, two regeneration nodules and one colonic metastasis. For six patients in whom histological proof was not available, the diagnosis of HCC was suggested based on markedly elevated serum alpha-fetoprotein levels. All but one (96%) of the 25 HCC demonstrated increased Doppler signal after Levovist. There were no Doppler signals before and after Levovist injection in three non-HCC lesions (two regeneration nodules and one colonic metastasis). Two patients (6.9%) suffered minor adverse reactions of nausea and vomiting. The results show that Levovist is safe and is able to improve lesion characterization and increase diagnostic confidence of hepatocellular carcinoma by enhancing tumour vascularization Doppler signal intensity.

Adult↗
PubMed1999

MR imaging of breast paraffinomas.

OBJECTIVE: Our objective is to present the MR appearance of breast paraffinoma, a late complication of breast augmentation by liquid paraffin wax, and to correlate this appearance with the histopathologic findings that were available for three of the 11 breasts we studied. CONCLUSION: Breast paraffinomas have a characteristic MR appearance that correlates well with histopathologic findings. With MR imaging, we were able to visualize the location and extent of the paraffinoma, best seen on the fat-suppression sequence, and to evaluate the surrounding fibroglandular breast tissue.

Aged↗
PubMed1997

Childhood intussusception: ultrasound-guided Hartmann's solution hydrostatic reduction or barium enema reduction?

A comparison was made of the efficacy of ultrasound guided Hartmann's solution hydrostatic reduction on 23 patients (US group) with the same number of consecutive patients in whom hydrostatic reduction was done by barium enema (BE group) under fluoroscopy for childhood intussusception. The US group was diagnosed by ultrasound scan and reduction was attempted under the guidance of ultrasonography with Hartmann's solution at 100 mm Hg pressure. Excluded were patients older than 12 years, patients in shock, patients with peritonitis, bowel perforation, and gross abdominal distension as well as recurrent intussusception of more than three episodes. There were three patients excluded in this group. The diagnosis of intussusception and complete reduction were confirmed by gastrografin enema. This US group had three recurrences (3 of 26, 11.5%), one lead point (1 of 23, 4.4%), and 19 successful reductions (19 of 26, 73%). Incidentally, there were also three patients excluded in this period of barium enema reduction. There was only one recurrence (1 of 24, 4.2%), one leadpoint (1 of 23, 4.4%), and 12 successful reductions (12 of 24, 50%) in these 23 BE patients. The success rates for the ileo-colic intussusceptions with Hartmann's solution reduction and barium enema reduction were 91% (19 of 21) and 55% (12 of 22), respectively (P = .00865). There was no complication in either group, and the accuracy of diagnosing a complete reduction was 100% in both forms of reduction. Hence, ultrasound-guided hydrostatic reduction for childhood ileocolic intussusception is preferred because it is safe, accurate, has a higher success rate, and can avoid radiation exposure risk.

Barium Sulfate↗
PubMed1997

Ileoileocolic intussusception in children: diagnosis and significance.

The ileoileocolic type of childhood intussusception is difficult to diagnose pre-operatively and is associated with increased morbidity. This study describes the clinical and imaging features of 10 consecutive ileoileocolic intussusceptions diagnosed ultrasonically in 10 patients over a 36 month period. Ultrasound-guided hydrostatic reduction using Hartmann's solution was attempted in all 10 patients. Clinical and imaging features were compared with those of 28 ileocolic intussusceptions in 25 patients diagnosed and treated using the same methods during the same period. Most of the clinical and plain radiographic features of the patients with the ileoileocolic and ileocolic types of intussusception were similar. The two types of intussusception had the classical doughnut or pseudokidney, or both, signs on pre-reduction ultrasound scans. During the reduction process, when surrounded by fluid within the caecal lumen, the ileoileocolic type of intussusception had a typical complex appearance due to frond-like loops of intussuscepted small bowel. This finding was present in all cases. The hydrostatic reduction rate was only 10% (1/10) for ileoileocolic intussusception, compared with 92.9% (26/28) for the ileocolic type. All unsuccessfully-reduced cases underwent surgery, with surgical confirmation of the intussusception type in all cases. Only one patient was found to have a lead point, caused by a Meckel's diverticulum. In conclusion, the diagnosis of ileoileocolic intussusception can be made pre-operatively and these patients require surgical management.

Child↗
PubMed1996

Sonographically guided hydrostatic reduction of childhood intussusception using Hartmann's solution.

OBJECTIVE: Currently, the standard methods for therapeutic reduction of intussusception in children involve considerable ionizing radiation. This study tested the effectiveness of sonographically guided hydrostatic reduction of intussusception using Hartmann's solution, a fluid with near-physiologic composition. SUBJECTS AND METHODS: Between March 1, 1994, and January 31, 1996, all children clinically suspected of having intussusception were evaluated by sonography. Those with positive findings on sonography were entered into the study and underwent confirmatory sonographically guided meglumine diatrizoate enema. During continuous sonographic monitoring, we used Hartmann's solution for attempted reduction of intussusception. Criteria for successful reduction were disappearance of the intussusceptum and passage of fluid through the ileocecal valve. Another sonographically guided meglumine diatrizoate enema was used to confirm successful reduction. RESULTS: We detected 25 consecutive intussusceptions in 22 patients. The patients were 12 girls and 10 boys, with a mean age of 14 months (range, 1-72 months). Sonograms revealed in all patients doughnut or pseudokidney signs or both. The sites of intussusception were the transverse colon (17 of 25), hepatic flexure (4 of 25), ascending colon (2 of 25), splenic flexure (1 of 25), and descending colon (1 of 25). Other findings were dilated fluid-filled small bowel (11 of 25) and free intraperitoneal fluid (9 of 25). The success rate of our sonographically guided attempts at hydrostatic reduction was 76% (19 of 25). Success was proven by meglumine diatrizoate enema in all 19 patients. The mean time of the reduction procedure was 18 min (range, 2-45 min). No complications occurred. All six patients in whom hydrostatic reduction was unsuccessful underwent surgery. Five of these patients had ileoileocolic intussusceptions. On sonography, when surrounded by fluid, ileoileocolic intussusceptions had a typically complex, fronded appearance. The remaining patient in whom hydrostatic reduction was unsuccessful had ileocolic intussusception. Of six ileoileocolic intussusceptions, one was hydrostatically reduced and a second was converted into an ileoileal intussusception before requiring surgery. The other four intussusceptions were surgically treated. CONCLUSION: Our data suggest that sonographically guided hydrostatic reduction with Hartmann's solution can be used to treat ileocolic intussusception and to diagnose ileoileocolic intussusception.

Catheterization↗
PubMed1994

Plasma degradation of platelet-activating factor in severely ill patients with clinical sepsis.

OBJECTIVE: To study the plasma degradation of platelet-activating factor in severely ill patients with clinical sepsis. DESIGN: A prospective, nonrandomized control study. SETTING: Intensive care unit in a university hospital. PATIENTS: Thirteen critically ill male patients with clinical sepsis, due to medical or surgical illness, and ten normal male volunteers were studied. Measurements were repeated in seven patients who survived. MEASUREMENTS AND MAIN RESULTS: The plasma activity of acetylhydrolase, the lipoprotein-associated enzyme that hydrolyses platelet-activating factor to its biologically inactive lyso-derivative was determined using an optimized enzyme assay. The plasma half-life of platelet-activating factor was also measured, along with phospholipase A2 activity, lyso-platelet-activating factor, and serum lipid concentrations. Patients results were compared with those results of normal controls and followed once in survivors. Acetylhydrolase activity in the patient group was significantly lower than in normal subjects (median 34, interquartile range 17 to 54 nmol/min/mL vs. median 60, interquartile range 56 to 80 nmol/min/mL; p < .002), while overall, the plasma half-life of platelet-activating factor did not differ significantly between the groups. However, the half-life of platelet-activating factor in six patients who died (median 3.3, range 3.3 to 4.3 mins) was significantly greater than in either survivors (median 2.1, range 1.4 to 2.9 mins; p < .001) or the normal group (median 2.5, range 2.2 to 2.8 mins; p < .001). Consistent with theoretical prediction, a significant linear relationship existed between platelet-activating factor half-life and the reciprocal of acetylhydrolase activity in the patient group (p < .05). Plasma phospholipase A2 activity was markedly increased in the patient group, while plasma lyso-platelet-activating factor and serum lipid concentrations were severely decreased. CONCLUSIONS: Depression of acetylhydrolase activity was consistent with the concentration of lipids with which it is associated. Platelet-activating factor half-life was relatively well preserved because of the nature of its relationship with enzyme activity. The half-life was prolonged in those patients with the worst outcome and the breakdown in plasma degradation of platelet-activating factor could have contributed to pathophysiology in these subjects.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1994

Variant of the Triple A syndrome.

The Triple A syndrome is a rare condition comprising achalasia, alacrima and adrenocorticotrophic hormone (ACTH) insensitivity. A 12 year old Chinese girl with a variant of this syndrome (achalasia and alacrima), presenting with failure to thrive, is reported. Typical appearances of achalasia on barium swallow subsequently led to the correct diagnosis. The radiologist may be the first to recognize this syndrome and hence help anticipate its potentially life-threatening sequelae.

Adrenocorticotropic Hormone↗
PubMed1992

The effects of a PAF antagonist on ischemic myocardial damage and arrhythmia in the dog.

Myocardial ischemia is associated with accumulation of lyso-phospholipids, including lyso-platelet activating factor, the degradation product and precursor of platelet activating factor. These compounds produce cellular and microvascular damage and, in the myocardium, depression of contractility and arrhythmia. The potent platelet activating factor antagonist, WEB 2086, or placebo, was infused (IV) 10 min before constriction of the proximal left anterior descending coronary artery in open-chest dogs. Two protocols were followed: the dose of WEB 2086 was 0.5 mg/kg in those subjected to 20 min ischemia with 10 min reperfusion (n = 40) and 5 mg/kg preceding 60 min ischemia alone (n = 24). There was no significant difference in the number of ventricular premature complexes between WEB 2086 and placebo treated dogs during either period of ischemia. On reperfusion in those surviving 20 min of ischemia, 5 of the 18 WEB 2086 and 9 of the 18 placebo treated dogs developed ventricular fibrillation (NS). After 60 min of myocardial ischemia, there was no statistical difference in histological changes (nuclear swelling, aggregation of chromatin, myofibrillar separation) between groups. Hence, no substantial effect of relatively large doses of WEB 2086 on ischemia-induced histological change or arrhythmia was found in this preparation.

Animals↗
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

Plasma platelet activating factor degradation and serum lipids after coronary bypass surgery.

OBJECTIVE: Platelet activating factor (PAF) is a potent mediator in inflammatory responses and maybe involved in various disease states. Degradation of PAF in plasma results from the action of a specific, lipoprotein associated, acetylhydrolase. The aim was to determine plasma acetylhydrolase activity under optimised conditions, PAF half life, phospholipase A2 activity, the lyso-derivative of PAF (lyso-PAF), and lipids in patients undergoing coronary artery bypass grafting. METHODS: The study variables were determined 3 d and 7 d following coronary artery surgery and compared to presurgical values in 15 males, age 55(SEM 4) years. RESULTS: Three days following coronary bypass grafting, total, LDL and HDL cholesterol fell significantly by 30%, 45%, and 15% respectively (p less than 0.001), all decreases correlating with bypass time (p less than 0.025). Concentrations remained low at 7 d (p less than 0.005). Acetylhydrolase activity fell by 38% (p less than 0.001) at 3 d post-surgery and remained depressed, but plasma PAF half life did not change after surgery. The inverse relationship between acetylhydrolase activity and plasma PAF half life preoperatively (p less than 0.01) was not evident after surgery. There was a direct linear relationship between acetylhydrolase activity and both total (p less than 0.002) and LDL cholesterol (p less than 0.001) before surgery. The fall in acetylhydrolase activity correlated with the fall in these lipids (p less than 0.01) but not with that of HDL cholesterol. Plasma lyso-PAF decreased by 65% (p less than 0.001) at 3 d and remained depressed (p less than 0.001). Plasma phospholipase A2 activity increased by 60% (p less than 0.01) and remained raised (p less than 0.05), the increase at 3 d being related to bypass time (p less than 0.05). CONCLUSIONS: The large fall in plasma acetylhydrolase activity after coronary bypass grafting is consistent with the fall in plasma lipids. However, the absence of a significant change in the measured PAF half life in plasma raises questions as to the pathophysiological significance of the decrease in acetylhydrolase activity.

Carboxylic Ester Hydrolases↗
PubMed1992

Effect of WEB 2086 on myocardial infarct size and regional blood flow in the dog.

OBJECTIVE: Systemic administration of platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-phosphocholine) produces hypotension and decreased cardiac output; in isolated heart preparations PAF increases coronary vascular resistance and depresses inotropic state. A precursor of PAF bioactivity has been found early in myocardial ischaemia and other reports have suggested that PAF antagonists can reduce myocardial damage and ventricular arrhythmia. This study concerns the effects of WEB 2086, a PAF antagonist, on myocardial infarct size and coronary blood flow after total coronary artery occlusion. METHODS: Open chest anaesthetised dogs (n = 26) were pretreated with either WEB 2086 (5 mg.kg-1) or saline before proximal occlusion of the circumflex artery and constant infusion of WEB 2086 (1 mg.kg-1.h-1) or saline was maintained for 5 h. Cardiac output and regional myocardial flow were measured with radiolabelled microspheres (46Sc, 57Co, and 113Sn) before and immediately after occlusion and 5 h later. In the 22 dogs surviving occlusion, infarct size was determined by planimetry of cross sectional slices after exposure to triphenyltetrazolium chloride. RESULTS: Infarct size was not different between treated and control groups, at 23.6(SEM 2.3)% v 24.8(3.7)% of left ventricle, and was not different between groups when related to vasculature at risk and to collateral blood flow determined with microspheres. CONCLUSIONS: No beneficial effect of a relatively large dose of the potent PAF antagonist, WEB 2086, on myocardial infarct size or collateral blood flow was found after relatively short duration of myocardial ischaemia in the dog.

Animals↗
PubMed1992

Plasma phospholipase A2 activity in clinical acute myocardial infarction.

1. Phospholipase A2 (PLA2) cleaves phospholipids to produce a lyso-phospholipid and free fatty acid and, in view of the biological activity of the products, PLA2 may play a role in many disease states. Lyso-phospholipids and free arachidonic acid increase in ischaemic myocardium, indicating that ischaemia activates the enzyme. 2. Plasma PLA2 activity was measured in patients with acute myocardial infarction, based on the release of labelled arachidonic acid from Escherichia coli cell membrane. Fourteen males (peak serum creatine phosphokinase (CK) above twice upper normal) were studied on day 1 (within 6 h of chest pain onset), days 2-4, and days 6-9. Normal age matched males (n = 13) were also studied. 3. Plasma PLA2 in patients with uncomplicated myocardial infarction (n = 12) was, initially, 1.14 +/- 0.10 (s.e.m.) nmol/min per mL plasma, similar to that in the normal group (1.52 +/- 0.14). On days 2-4, PLA2 activity increased to 1.94 +/- 0.18 (P less than 0.001) and this activity was correlated with the earlier peak CK level (P less than 0.02). On days 6-9, PLA2 activity was 1.49 +/- 0.13 while in two patients who developed complications and underwent open-heart surgery between the last two measurements, there were further increases to 4.22 and 4.04 nmol/min per mL. 4. The increase in plasma PLA2 in uncomplicated myocardial infarction is likely to be due to release from the damaged myocardium; whether it contributes to pathophysiology is uncertain.

Adult↗
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↗