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Biomedical subjects

L L Chan

Publications and source records attributed to L L Chan.

At least 37 records · Page 2Linked to original sources
PubMed2004

Audit of diagnostic and interventional craniocervical catheter angiographic procedures at the Singapore General Hospital.

INTRODUCTION: Catheter angiography is an established imaging modality of evaluating cerebral and head and neck vascular diseases. It is, however, an invasive procedure with a small risk of complications. The aim of our study was to evaluate the prevalence of peri-procedural complications in a local hospital setting. MATERIALS AND METHODS: A total of 88 patients underwent diagnostic and interventional craniocervical procedures over 6 months in our department. The casenotes of 83 patients were retrospectively reviewed for complications arising from a total of 99 procedures carried out. RESULTS: A new focal neurological deficit developed in 3 different patients after a procedure, giving a prevalence of 3.0%. All these occurred in diagnostic procedures and were permanent deficits with correlative computed tomography (CT) or magnetic resonance (MR) imaging findings of acute cerebral infarction. All these occurred in high-risk patients who had severe underlying cerebrocarotid vascular compromise. There was 1 case of contrast medium-induced nephropathy (1.0%), occurring in a patient with pre-existing renal impairment. Local complications included 1 case of iatrogenic external iliac artery dissection (1.0%) and 5 cases (5.1%) of small and uncomplicated puncture site groin haematomas. CONCLUSION: The most significant complication associated with a craniocervical angiographic procedure was the development of post-procedural stroke in patients with significant preexisting cerebrocarotid vascular compromise. In the absence of this risk factor, craniocervical catheter angiography is a relatively safe procedure.

Adolescent↗
PubMed2004

Case reports of two biopsy-proven patients with Creutzfeldt-Jakob disease in Singapore.

INTRODUCTION: Creutzfeldt-Jakob disease (CJD) is the most common transmissible human subacute spongiform encephalopathy. There is limited literature on CJD in Southeast Asia. We describe the clinical course and diagnostic evaluation of 2 Singapore patients with biopsy-proven CJD. CLINICAL PICTURE: Two patients presented with non-specific symptoms such as withdrawal, forgetfulness, asthenia, giddiness and insomnia. Both patients had spontaneous myoclonic jerks and impairment of multiple neurologic systems (visual, pyramidal, cerebellar and neurocognitive systems). Magnetic resonance imaging and electroencephalography provided helpful supportive evidence. Diagnosis of CJD was established on brain biopsy. Histological features included spongioform degeneration, neuronal cell loss and astrocytosis. TREATMENT/OUTCOME: Treatment remains palliative. Deterioration in their clinical condition was relentless, progressing to a totally dependent state within 10 to 12 months. CONCLUSION: The early features of CJD can be varied and non-specific. It is important for physicians from different specialties to be cognisant of the clinical manifestations of CJD and the appearance of supportive and definitive investigations.

Biopsy, Needle↗
PubMed2003

Levodopa-induced oromandibular dystonia in progressive supranuclear palsy.

Levodopa-induced dyskinesias have been reported in Parkinson's disease and multiple system atrophy. Cranial dystonias are rare in patients with progressive supranuclear palsy (PSP). In this report we describe an unusual case of reversible levodopa-induced Oromandibular dystonia (OMD) in a PSP patient to highlight the importance of recognizing this drug related complication in the management of PSP, and discuss the possible underlying pathophysiology.

Aged↗
PubMed2002

Cellular lipid peroxidation end-products induce apoptosis in human lens epithelial cells.

Hydrogen peroxide (H(2)O(2)), an oxidant present in high concentrations in the aqueous humor of the elderly eyes, is known to impart toxicity to the lens---apoptosis being one of the toxic events. Since H(2)O(2) causes lipid peroxidation leading to the formation of reactive end-products, it is important to investigate whether the end-products of lipid peroxidation are involved in the oxidation-induced apoptosis in the lens. 4-Hydroxynonenal (HNE), a major cytotoxic end product of lipid peroxidation, has been shown to mediate oxidative stress-induced cell death in many cell types. It has been shown that HNE is cataractogenic in micromolar concentrations in vitro, however, the underlying mechanism is not yet clearly understood. In the present study we have demonstrated that H(2)O(2) and the lipid derived aldehydes, HNE and 4-hydroxyhexenal (HHE), can induce dose- and time-dependent loss of cell viability and a simultaneous increase in apoptosis involving activation of caspases such as caspase-1, -2, -3, and -8 in the cultured human lens epithelial cells. Interestingly, we observed that Z-VAD, a broad range inhibitor of caspases, conferred protection against H(2)O(2)- and HNE-induced apoptosis, suggesting the involvement of caspases in this apoptotic system. Using the cationic dye JC-1, early apoptotic changes were assessed following 5 h of HNE and H(2)O(2) insult. Though HNE exposure resulted in approximately 50% cells to undergo early apoptotic changes, no such changes were observed in H(2)O(2) treated cells during this period. Furthermore, apoptosis, as determined by quantifying the DNA fragmentation, was apparent at a much earlier time period by HNE as opposed to H(2)O(2). Taken together, the results demonstrate the apoptotic potential of the lipid peroxidation end-products and suggest that H(2)O(2)-induced apoptosis may be mediated by these end-products in the lens epithelium.

Aldehydes↗
PubMed2002

Neurological changes following radiation therapy for head and neck tumours.

Radiation therapy is widely used in the treatment of head and neck tumours either as a primary form of treatment or a supplementary modality. Although the benefits of radiation therapy are well established, this treatment modality is not without untoward consequences and complications. The intent of this paper is to highlight the neurological complications that may follow the treatment for head and neck malignancies, in particular, following radiation therapy for nasopharyngeal carcinoma.

Brain Stem↗
PubMed2002

Evolving spectrum of movement disorders in extrapontine and central pontine myelinolysis.

Extrapontine (EPM) and central pontine myelinolysis (CPM) are rare and frequently related to rapid correction of hyponatremia. We describe a 60-year-old woman who developed an unusual evolving spectrum of movement disorders secondary to EPM and CPM following intravenous sodium replacement therapy for severe hyponatremia. She presented initially with confusion, generalized coarse postural limb tremor, myoclonic jerks and quadriparesis. Subsequently her mental state improved and her tremor and weakness resolved. Over the following months, she developed progressive painful dystonia of her facial musculature and lower limbs. This gradually became generalized and associated with choreoathethosis in her limbs. In addition, she had increasing bradykinesia and rigidity, which responded poorly to levodopa treatment. Our case illustrates that while the myelin destruction occurs during the initial insult of the osmotic demyelinating process, its delayed clinical effects resulting from ineffective reorganization of neuronal structures may be progressive, evolve with time, and difficult to treat.

Disease Progression↗
PubMed2002

Post-epidural analgesia spinal cord infarction: MRI correlation.

Permanent neurological deficits after epidural analgesia are rare, but have long been believed to be caused by cord ischaemia when no obvious cause is demonstrable. The mechanisms of this injury are uncertain, but a literature review suggests important risk factors. We report a first case of extensive spinal cord infarction confirmed by magnetic resonance imaging (MRI) following post-thoracotomy epidural analgesia and review the literature to explain the mechanism underlying this devastating complication.

Analgesia, Epidural↗
PubMed2002

MRI of cochlear otosclerosis.

Cochlear otosclerosis is an uncommon cause of mixed and sensorineural hearing loss. This has a characteristic appearance on CT, producing a distinctive pericochlear hypodense double ring. However, its appearance on MRI is not as readily appreciated, producing a ring of intermediate signal in the pericochlear and perilabyrinthine regions on T(1) weighted images, demonstrating mild to moderate enhancement after gadolinium administration. Increased signal on T(2) weighted images may also be seen. Recognition of these MRI features is important as MRI may be the first modality of investigation, especially when patients present with symptoms indicative of sensorineural hearing loss. We review four patients who presented with sensoineural hearing loss, and who were imaged with MRI as the first line of investigation.

Cochlea↗
PubMed2002

Diffusion weighted MR imaging in acute stroke: the SGH experience.

Cerebrovascular accident (CVA) is a leading cause of death and disability in many countries. Diffusion-weighted (DW) magnetic resonance (MR) imaging has been reported to be useful in the detection of acute strokes and as an investigative tool evaluating the therapeutic effects of neuroprotective and thrombolytic agents. The objectives of this study are to share our experience using the commercially available isotropic DW scan in imaging of acute stroke, assess its usefulness over conventional T2-weighted (T2W) scans in a busy clinical radiology unit and highlight it pitfalls. We found the rapid sub-minute DW technique well suited for ill and restless stroke patients and superior to T2W scans in many ways. It was highly sensitive to acute ischaemic lesions, made lesions easily identifiable and readily differentiated the acute lesion from a background of multiple chronic infarcts. However, there are potential pitfalls in the evaluation of small hyperacute posterior fossa strokes and venous infarcts. The major strength of this MR technique lies in its ability to diagnose hyperacute strokes and thence the potential for therapeutic thrombolysis, but unfortunately patients qualifying for the "therapeutic window" were a minority. More efforts need to be focused on public education in order for this powerful imaging modality to find its true value and contribute to viability of an effective thrombolytic programme.

Adult↗
PubMed2002

Seroepidemiology of toxoplasmosis among HIV-infected patients and healthy blood donors.

A cross-sectional study was carried out in University of Malaya Medical Centre, Kuala Lumpur. Blood samples from 100 HIV-infected patients and 203 Healthy Blood Donors (HBD) were collected and anti-Toxoplasma antibodies were detected by using conventional ELISA. The seroprevalence of toxoplasmosis in HIV/AIDS and Healthy Blood Donors were found to be 21% and 28.1% respectively. There was no significant association between the seroprevalence of toxoplasmosis and various possible risk factors i.e. contact with cat, consumption of undercooked meat and history of blood transfusion in both groups. No significant differences between Toxoplasma seroprevalence in HIV/AIDS and Healthy Blood Donors in association with presence of single or multiple risk factors were found. The mean CD4 count among HIV/AIDS patients in this study was 202.23 cell/cumm. There was no significant association between CD4 count and seropositivity for Toxoplasma antibodies in HIV/AIDS patients.

Adolescent↗
PubMed2002

Enzyme replacement therapy for Gaucher Disease: the only experience in Malaysia.

Gaucher Disease may now be treated with enzyme replacement therapy (ERT) or bone marrow transplantation (BMT). Both have their advantages and disadvantages. Results with BMT are curative when successful but limited by the scarcity of an appropriate donor. ERT offers very good relief of symptoms but treatment is lifelong and cost of treatment exorbitant. Patients in developing countries are particularly disadvantaged and management remains a dilemma for both doctor and patient.

Child↗
PubMed2001

Reversible parkinsonism in systemic lupus erythematosus.

Parkinsonism as a manifestation of central nervous system (CNS) lupus is extremely rare. We report the first patient with systemic lupus erythematosus (SLE) who developed a reversible parkinsonian syndrome associated with enhancing subcortical lesions on magnetic resonance imaging (MRI). Following treatment with prednisolone and cyclophosphamide, her bradyphrenia, bradykinesia, hypophonia, rigidity, and abnormal gait progressively improved. Three months after she commenced treatment, repeat MRI scanning demonstrated resolution of the abnormal subcortical white matter enhancement. Our case illustrates unusual clinico-radiologic correlates of reversible parkinsonism in a SLE patient; these findings suggest that disruption of the subcortical frontal pathways may be a possible pathophysiologic mechanism for parkinsonism in cerebral lupus.

Brain↗
PubMed2001

Involvement of caspases in 4-hydroxy-alkenal-induced apoptosis in human leukemic cells.

4-Hydroxynonenal (HNE), a reactive and cytotoxic end-product of lipid peroxidation, has been suggested to be a key mediator of oxidative stress-induced cell death and in various cell types has been shown to induce apoptosis. We have demonstrated that HNE, at micromolar concentrations, induces dose- and time-dependent apoptosis in a leukemic cell line (CEM-C7). Interestingly, much higher concentrations of HNE (> 15-fold) were required to induce apoptosis in leukocytes obtained from normal individuals. We also demonstrate that HNE causes a decrease in clonogenicity of CEM-C7 cells. Furthermore, our data characterize the caspase cascade involved in HNE-induced apoptosis in CEM-C7 cells. Using specific fluorogenic substrates and irreversible peptide inhibitors, we demonstrate that caspase 2, caspase 3, and caspase 8 are involved in HNE-induced apoptosis, and that caspase 2 is the first initiator caspase that activates the executioner caspase 3, either directly or via activation of caspase 8. Our studies also suggest the involvement of another executioner caspase, which appears to be similar to caspase 8 but not caspases 2 and 3, in its specificity. The demonstration of decreased clonogenicity by HNE in the leukemic cells, and their higher susceptibility to HNE-induced apoptosis as compared to the normal cells, suggests that such compounds may have potential for leukemia chemotherapy.

Aldehydes↗