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Biomedical subjects

W S Poon

Publications and source records attributed to W S Poon.

At least 73 records · Page 4Linked to original sources
PubMed2002

Inferior vena caval filters following deep vein thrombosis in patients with ruptured intracranial aneurysm.

Anticoagulant therapy is highly effective and prevents death in more than 95% of patients who have suffered pulmonary embolism following deep vein thrombosis. Inferior vena caval filters provide an alternative to full anticoagulation in those patients at highest risk of catastrophic haemorrhagic complications. We report on two patients who developed deep vein thrombosis following ruptured unsecured intracranial aneurysms. Inferior vena caval filters were inserted prior to aneurysm clipping, as a prophylactic measure to prevent pulmonary embolism while awaiting surgery. The patients did not receive anticoagulant therapy following successful clipping of the aneurysm. Both patients had clinical resolution of the lower limb swelling and no radiological evidence of propagation of the thrombus. During 18 months of follow-up there were no complications and no evidence of post-thrombotic syndrome.

Aneurysm, Ruptured↗
PubMed2001

Heterogeneous responses of aquaporin-4 in oedema formation in a replicated severe traumatic brain injury model in rats.

Aquaporin-4 (AQP4) is the most abundant water channel in the rat brain. In this study, the distribution pattern and mRNA expression levels of AQP4 were examined in a severe traumatic brain injury model by immunohistochemistry and reverse transcription-polymerase chain reaction. Oedema formation and blood-brain barrier (BBB) integrity were assessed by wet-dry weight measurements and immunostaining of endogenous IgG respectively. In the oedematous contusional cortex with impaired BBB integrity, negative immunostaining of AQP4 and down-regulation of its mRNA level were identified (P<0.05) at 1 day post-injury, while in other oedematous regions of the injured brain where BBB was intact, there was no significant change in the AQP4 expression level. This heterogeneous pattern of AQP4 responses can be interpreted as follows: focal brain injury (such as a contusion) with impaired BBB resulting in vasogenic oedema is associated with reduction of AQP4 expression, whereas, in cytotoxic oedema, associated with diffuse brain injury with intact BBB, changes in AQP4 expression are not significant. This study provides basic information for investigating new treatments for traumatic brain oedema.

Animals↗
PubMed2001

The management of residual and recurrent intracranial aneurysms after previous endovascular or surgical treatment--a report of eighteen cases.

OBJECT: We wish to report our experience in the management of residual or recurrent intracranial aneurysm after previous endovascular or surgical treatment. METHODS: We performed a retrospective review of the clinical notes, operation records and cerebral angiograms of eighteen patients who were known to have undergone treatment for residual or recurrent aneurysms. RESULTS: During the period of April 1994 to May 1999, 210 patients were treated for an intracranial aneurysm either surgically or by endovascular methods. Eighteen of these patients (8.6%) were subsequently treated for residual or recurrent aneurysm. Thirteen achieved a complete occlusion. Complete occlusion was achieved in five of the eight patients who underwent endovascular treatment as a second procedure. Seven out of ten surgical cases achieved complete occlusion. Fifteen patients made a good recovery according to the Glasgow Outcome Score. Two patients who presented in a poor grade subarachnoid haemorrhage (SAH) were left severely disabled. One patient died after retreatment. CONCLUSIONS: The treatment of cerebral aneurysm remnants can be performed effectively using a variety of modalities. The original purpose of the treatment, which is total occlusion of the lesion, can thus be achieved.

Adult↗
PubMed2001

The comparative impact of video-consultation on neurosurgical health services.

This study evaluated the impact of telemedicine technology on the provision of neurosurgical health services. We focused on the differences between the use of real time audio-visual teleconferencing and teleradiology versus conventional telephone consultations in the referral of neurosurgical patients from a large district general hospital. All patients requiring emergency neurosurgical consultation were included for randomization into telephone consultation only (Mode A), teleradiology and telephone consultation (Mode B) and video-consultation (Mode C). Measures of effectiveness included diagnostic accuracy and adverse events during the transfer and Glasgow Outcome Score. In a 10-month period, 327 patients were recruited and randomized into the study: the male/female ratio was 2:1 and the number of patients required to be transferred to the neurosurgical unit was 125 (38%). There was a trend towards a more favourable outcome in the video-consultation mode (44%, Mode C), versus teleradiology (31%, Mode B), versus telephone consultation (38%, Mode A). The interim data of this prospective randomized trial suggests that video-consultation may have a favourable impact on emergency neurosurgical consultations.

Emergencies↗
PubMed2001

Pre-operative grading of intracranial glioma.

AIM: To compare the accuracy of MR-determined cerebral blood volume (CBV) maps with SPECT imaging with thallium-201 in pre-operative grading of intracranial glioma. MATERIAL AND METHODS: Nineteen patients (7 female and 12 male, mean age 46.8 years) with intracranial gliomas were examined with MR perfusion imaging pre-operatively. Sixteen of these patients were also examined with SPECT imaging with thallium-201. The tumour to contralateral white matter NI (negative integral) and tracer uptake ratios were evaluated. The ratios in high-grade and low-grade tumours were compared. RESULTS: The maximum CBV ratios of grades I and II gliomas (2.958+/-2.217) were significantly lower than the maximum CBV ratio of grades III and IV (9.484+/-4.520), p<0.001. There was no statistical difference when CBV ratios of grades I and II (p=0.381), grades II and III (p=0.229) and grades III and IV (p=0.476) gliomas were compared. Thallium SPECT imaging showed no difference in tumour uptake ratio between low-grade and high-grade gliomas (p=0.299). CONCLUSION: MR-determined NI was useful for pre-operative grading of intracranial gliomas but SPECT thallium-201 imaging was not.

Adolescent↗
PubMed2001

Detection of multiple gene amplifications in glioblastoma multiforme using array-based comparative genomic hybridization.

We have used a new method of genomic microarray to investigate amplification of oncogenes throughout the genome of glioblastoma multiforme (GBM). Array-based comparative genomic hybridization (array CGH) allows for simultaneous examination of 58 oncogenes/amplicons that are commonly amplified in various human cancers. Amplification of multiple oncogenes in human cancers can be rapidly determined in a single experiment. Tumor DNA and normal control DNA were labeled by nick translation with green- and red-tagged nucleotides, respectively. Instead of hybridizing to normal metaphase chromosomes in conventional comparative genomic hybridization (CGH), the probes of the mixed fluorescent labeled DNA were applied to genomic array templates comprised of P1, PAC, and BAC clones of 58 target oncogenes. The baseline for measuring deviations was established by performing a series of independent array CGH using test and reference DNA made from normal individuals. In the present study, we examined fourteen GBMs (seven cell lines and seven tumours) with CGH and array CGH to reveal the particular oncogenes associated with this cancer. High-level amplifications were identified on the oncogenes/amplicons CDK4, GLI, MYCN, MYC, MDM2, and PDGFRA. The highest frequencies of gains were detected on PIK3CA (64.3%), EGFR (57.1%), CSE1L (57.1%), NRAS (50%), MYCN (42.9%), FGR (35.7%), ESR (35.7%), PGY1 (35.7%), and D17S167 (35.7%). These genes are suggested to be involved in the GBM tumorigenesis.

Brain Neoplasms↗
PubMed2001

Spinal cord pilocytic astrocytoma with cranial meningeal metastases.

Dissemination of tumour cells along the cerebrospinal fluid (CSF) pathway has been reported mostly in medulloblastomas, germ cell tumours or high grade gliomas. Juvenile pilocytic astrocytoma (JPA) is usually a benign astrocytoma. However, drop metastases of indolent nature from intracranial tumours to the spinal cord are documented. All of the previously reported cases represent metastases of cerebellar or hypothalamic tumours spreading to the spinal cord. We document in this paper the first report of a spinal cord pilocytic astrocytoma spreading via the CSF to the cerebral meninges. A 9 year old girl had a JPA of C5 to C7 subtotally resected. Two and a half years later she presented with hydrocephalus with radiologically meningeal enhancement. The meninges were biopsied which showed metastatic JPA. The girl was relatively well 4 years after initial surgery with residual tumour. Spinal cord JPA can rarely metastasize to the cranial meninges. Similar to intracranial tumours which spread to the spinal cord, such metastatic lesions are indolent.

Astrocytoma↗
PubMed2001

The impact of an armless frameless neuronavigation system on routine brain tumour surgery: a prospective analysis of 51 cases.

A passive infrared armless and frameless neuronavigation system was introduced in routine intracranial and skull base surgery, and its impact on 51 cases in a one year period was assessed. No cases were rejected by the operating surgeon for lack of accuracy (> 3 mm). Operating time was not significantly lengthened, except in transphenoidal cases (255 +/- SD 168 min versus 185 +/- SD 119 min, p = 0.02). Length of stay was shorter in navigation cases in supratentorial glioma (12 +/- SD 7.3 days versus 15 +/- SD 7.9 days) and meningioma (11 +/- SD 5.3 days versus 16 +/- SD 6.7 days, p = 0.01). Outcome at 3 months was comparable in both the supratentorial glioma and meningioma group. Problems such as setup time and brain shift are addressed and discussed.

Adolescent↗
PubMed2001

Does intensive rehabilitation improve the functional outcome of patients with traumatic brain injury? Interim result of a randomized controlled trial.

To evaluate the effects of intensive rehabilitation on the functional outcome in patients with traumatic brain injury (TBI), we carried out a randomized controlled assessor-blind trial, comparing two groups of patients receiving different intensities of rehabilitation treatment (2 versus 4 h per day). Patients with moderate and severe TBI, aged from 12 to 65 years, were included. Glasgow Outcome Scale (GOS) and Functional Independent Measurement (FIM) were assessed monthly. The interim results of 36 cases showed that there was a trend of more patients in the study group achieving full FIM scores, and good GOS at 2 and 3 months, but the control group appeared to be catching up towards 6 months. Intensive rehabilitation may improve the early functional outcome of TBI patients. The interim results indicate that the study should be continued.

Adolescent↗
PubMed2001

Concurrent hypermethylation of multiple genes is associated with grade of oligodendroglial tumors.

Current evidence suggests that epigenetic changes play an important role in the evolution of human cancers. In this study, we evaluated whether hypermethylation of CpG islands at the gene promotor regions of several tumor-related genes is involved in the carcinogenesis of oligodendroglial tumors. We examined the methylation status of 11 genes in a series of 43 oligodendroglial tumors (19 oligodendrogliomas, 13 anaplastic oligodendrogliomas, 9 oligoastrocytomas, and 2 anaplastic oligoastrocytomas) by methylation-specific polymerase chain reaction. Our results showed that hypermethylation of CpG islands was detectable in 8 of 11 genes studied and 74% of tumors were hypermethylated in at least 1 gene. Promotor hypermethylations were detected in O6-methylguanine-DNA methyltransferase (MGMT), RB1, estrogen receptor, p73, p16INK4a, death-associated protein kinase, p15INK4b, and p14ARF at 60%, 34%, 30%, 16%, 12%, 10%, 7%, and 2%, respectively. No hypermethylation was detected in the promotors of glutathione-S-transferase P1, von Hippel-Lindau or the DNA mismatch repair (hMLH1) genes. Statistical analysis revealed that concordant hypermethylation of at least 2 genes, p16INK4a and p15INK4b were significantly associated with anaplastic oligodendroglial tumors, and hypermethylation of MGMT was significantly associated with loss of chromosome 19q and with combined loss of chromosomes 1p and 19q. More importantly, several candidate tumor suppressor genes such as p16INK4a, p15INK4b, and p73 that were previously reported as unmutated in oligodendroglial tumors were found to be hypermethylated in their CpG islands. Taken together, we conclude that hypermethylation of CpG islands is a common epigenetic event that is associated with the development of oligodendroglial tumors.

Astrocytoma↗
PubMed2001

Analysis of loss of heterozygosity on chromosomes 10q, 11, and 16 in medulloblastomas.

OBJECT: The loss of genetic material from specific chromosome loci is a common feature in the oncogenesis of tumors and is often indicative of the presence of important tumor suppressor genes at these loci. Recent molecular genetic analyses have demonstrated frequent loss of chromosomes 10q, 11, and 16 in medulloblastomas. The aim of this study was to localize the targeted deletion regions on the three aforementioned chromosomes in medulloblastomas. METHODS: Loss of heterozygosity (LOH) was examined on chromosomes 10q, 11, and 16 in a series of 22 primary and two recurrent medulloblastomas by using polymerase chain reaction-based microsatellite analysis. The DNA extracted from the tumors and corresponding normal blood samples were amplified independently in the presence of radioactively labeled microsatellite primers, resolved by denaturing gel electrophoresis and processed for autoradiography. The DNA obtained from control blood samples that displayed allelic heterozygosity at a given microsatellite locus were considered informative. Loss of heterozygosity was inferred when the allelic signal intensity of the tumor sample was reduced by at least 40%, relative to that of the constitutional control. The LOH analysis demonstrated that deletions of chromosomes 10q, 11p, and 16q are recurrent genetic events in the development of medulloblastomas. Three subchromosomal regions of loss have been identified and are localized to the deleted in malignant brain tumors 1 [DMBT1] gene site on chromosomes 10q25, 11p13-11p15.1, and 16q24.1-24.3. CONCLUSIONS: These results indicate that DMBT1 is closely associated with the oncogenesis of medulloblastomas and highlight regions of loss on chromosomes 11p and 16q for further fine mapping and cloning of candidate tumor suppressor genes that are important for the genesis of medulloblastoma.

Adolescent↗
PubMed2001

Identification of novel regions of allelic loss in ependymomas by high-resolution allelotyping with 384 microsatellite markers.

OBJECT: Ependymomas are rare glial neoplasms; little is known about the molecular pathogenesis of this tumor entity. In a previous study the authors found multiple genomic imbalances in ependymomas resected in 20 adults and eight children, including loss of chromosomes 1p, 6, 16, 17, 19q, 20q, and 22q, as well as gain of chromosomes 4q, 5q, 7q, 9q, and 12q on comparative genomic hybridization. The aim of this study was to map in more detail the commonly affected regions in ependymomas. METHODS: A comprehensive allelotype analysis of 16 ependymomas was conducted using 384 microsatellite markers that span the 22 autosomes. Based on this high-resolution loss of heterozygosity analysis, multiple overlapping deletion regions were identified as follows: 6q25.2-27, 16p12-13.1, 16q22.3-24.1, 17q22-24, 19q12-13.2, 20q13.2-13.3, and 22q13.1-13.3. CONCLUSIONS: These data confirmed previous reports that loss of chromosomes 17 and 22 were common in ependymomas. Moreover, the authors were able to identify loss of chromosomes 13, 16, 19, and 20 as novel findings in ependymomas. It is believed that potential tumor suppressor genes that reside in these commonly deleted regions may contribute to the molecular tumorigenesis of ependymomas.

Adolescent↗
PubMed2001

Surgical management of Parkinson's disease: a critical review.

Parkinson's disease is a progressive disabling movement disorder that is characterised by three cardinal symptoms: resting tremor, rigidity, and bradykinesia. Before the availability of effective medical treatment with levodopa and stereotactic neurosurgery, the objective of surgical management was to alleviate symptoms such as tremor at the expense of motor deficits. Levodopa was the first effective medical treatment for Parkinson's disease, and surgical treatment such as stereotactic thalamotomy became obsolete. After one decade of levodopa therapy, however, drug-induced dyskinesia had become a source of additional disability not amenable to medical treatment. Renewed interest in stereotactic functional neurosurgery to manage Parkinson's disease has been seen since the 1980s. Local experience of deep-brain stimulation is presented and discussed in this paper. Deep-brain stimulation of the subthalamic nucleus is an effective treatment for advanced Parkinson's disease, although evidence from randomised control trials is lacking.

Humans↗
PubMed2001

Paradoxical enlargement of tuberculous brain abscess during drug treatment: a case report.

This is a case report of a patient suffering from tuberculous (TB) brain abscesses. Despite supervised and appropriate anti-TB chemotherapy, the size of the abscesses paradoxically increased, accompanied by clinical deterioration at 1 month. A second aspiration was performed which yielded a large amount of viable tubercle bacilli. The same drug regimen was continued. This was followed by complete resolution of the lesions in 12 months. Hence TB brain abscess which remains culture and smear positive after four weeks treatment may not represent treatment failure.

Antitubercular Agents↗