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Biomedical subjects

W S Poon

Publications and source records attributed to W S Poon.

At least 127 records · Page 7Linked to original sources
PubMed1996

Putaminal and thalamic hemorrhage in ethnic chinese living in Hong Kong.

BACKGROUND: Hemorrhagic stroke is very common in the Chinese population, and it is one of the leading causes of mortality in Chinese communities. The risk factors to explain this high incidence are unknown. It is the purpose of this study to look into the features of hemorrhagic stroke in the Hong Kong Chinese. METHODS: We conducted a prospective hospital-based study in which 60 consecutive Chinese patients with computed tomography diagnosis of putaminal or thalamic hemorrhage were included. Their demographic and clinical data were collected and analyzed. RESULTS: Two major findings evolved from the present study. (1) Unlike the Western studies, the majority of our patients were about a decade younger; (2) 50% of the patients had previously diagnosed hypertension, but only 20% of these patients were compliant with their antihypertensive medication. Our results also suggested that low admission Glasgow Coma Scale scores, large hematoma size, and the presence of intraventricular blood were associated with poor outcomes. CONCLUSIONS: This study concludes that hemorrhagic stroke is indeed a serious health problem in Hong Kong. Simple measures, such as improvement of health education and the primary care system in the management of hypertension, would help to reduce the incidence of hemorrhagic stroke.

Adult↗
PubMed1996

Cerebral venous oxygen saturation monitoring: is dominant jugular bulb cannulation good enough?

Venous oxygen saturation at the clinically dominant jugular bulb (SjO2) and that at the confluence of the cerebral sinuses (SccsO2) were compared by direct simultaneous blood sampling of 13 severely head injured patients. The side of dominant jugular bulb (JB) was determined by neck compression test. The right side was chosen if the test was equivocal. In effect, the right side was cannulated in all cases. Subsequent angiography showed that two of the 13 cases were left side dominant. In all, 176 pairs of blood samples were analysed. Correspondence rates (the difference between each pair of blood samples being less than 4% of oxygen saturation) for individual case were good (80-100%) in nine cases including one case with left side dominance. Correspondence rates were moderate in two cases (50 and 56%); the differences were not clinically significant. In the remaining two cases, including one with left side dominance, the correspondence rates were poor (0 and 4%, respectively); SccsO2 was always lower than SjO2; median differences were 13.4 and 23.1%. Ischemia in the cerebral hemispheres would have been underestimated if management were based on SjO2. Monitoring at the dominant JB accurately reflected the global and hemispheric cerebral oxygenation in 11/13 of cases. Monitoring at the non-dominant JB is not recommended.

Adolescent↗
PubMed1996

Histopathology of post-embolized meningiomas.

Although embolization of meningiomas has been performed for many years as a preoperative adjunct to reduce tumor vascularity and facilitate surgical excision, little has been written about the features of the histological artefacts introduced by the process. In particular, the fact that it may produce tumor necrosis may potentially cause confusion with atypical or malignant meningiomas. In this study, 25 meningeal tumors of different histological subtypes, all of which had been previously embolized, were reviewed histologically as well as with immunostaining for the MIBI antigen and proliferating cell nuclear antigen (PCNA). Necrosis, in the form of confluent necrosis as well as micronecrosis, was the most common feature (48%). Other characteristic features included florid ischemic changes (16%), intravascular Ivalon particles (24%), and fibrinoid necrosis of vascular walls (12%). Histological changes showed no obvious relationship with the interval between embolization and surgery. There was an increase in MIB1 and PCNA labelling indices in those tumor exhibiting necrotic foci, but it did not seem to have any prognostic significance. We believe pathologists should be familiar with the histological changes induced by embolization in meningiomas so that an erroneous diagnosis of a high-grade lesion will not be made.

Adult↗
PubMed1996

The role of computed tomographic angiography in the diagnosis of intracranial aneurysms and emergent aneurysm clipping.

Conventional cerebral angiography has always been regarded as the gold standard for intracranial aneurysm detection. However, conventional angiography has the disadvantages of being invasive and time consuming. We present here 30 patients who underwent computed tomographic angiography (CTA) with three-dimensional reconstruction for the detection of intracranial aneurysms. All of these patients had subarachnoid hemorrhage or suspected intracranial aneurysms. CTA was performed in all patients with the use of a General Electric Hispeed Advantage helical scanner. Iohexol, 135 ml, was used as the contrast agent. Twenty-five patients also underwent conventional angiography for comparison. The five patients who underwent CTA only did not have conventional angiography because of poor clinical condition, and four of them subsequently died. Five patients had subarachnoid hemorrhage, but the results of both CTA and conventional angiography were negative for aneurysms. One patient had an incidental finding of a 3-mm left posterior communicating artery aneurysm on CTA, which was confirmed by conventional angiography. In the remaining 19 patients, 19 saccular aneurysms and 1 fusiform aneurysm were detected by CTA. Locations and sizes were confirmed by conventional angiography in all except two. The first exception was a patient who had a 2.5-mm anterior communicating artery aneurysm detected by CTA but not by conventional angiography. Surgical exploration confirmed the CTA diagnosis. The other exception was a patient in whom a 2-mm right posterior communicating artery aneurysm was detected by CTA but in whom conventional angiography showed a 2-mm left posterior communicating artery aneurysm. Unfortunately, there was no surgical confirmation in this case because the family of the patient refused surgery. Our results have demonstrated that CTA is a quick, reliable, and relatively simple diagnostic tool for intracranial aneurysms. In an emergent situation, such as a deteriorating patient with a hematoma, it is superior to either empiric exploration or infusion computed tomographic scans because it delineates the orientation and configuration of the aneurysm and its associated vascular anatomy.

Adult↗
PubMed1996

Dural cavernous angiomas in a child.

Dural-based cavernous angiomas are rare intracranial vascular lesions. Most of the reported cases are located in the middle cranial fossa, and those located outside the middle fossa are even more uncommon. Thus far, only 3 pediatric cases have been reported and all of them were found outside the middle fossa of a neonate. We would like to add the fourth pediatric case of a dural-based cavernous angioma located in the posterior fossa of a 5-year-old boy.

Child, Preschool↗
PubMed1996

Atypical monoclonal plasma cell hyperplasia: its identity and treatment. Case report.

Atypical monoclonal plasma cell hyperplasia, like plasma cell granuloma, is an inflammatory pseudotumor. Both are extremely rare in the central nervous system. Atypical monoclonal plasma cell hyperplasia is a recently identified neuropathological entity described by Weidenheim, et al., in 1989. A second case of this disease entity is now reported. The histological findings that differentiate this lesion from plasma cell granuloma, plasmacytoma, and meningioma are discussed. The present case clearly demonstrates the complete resolution of the disease after a course of fractionated radiotherapy.

Brain Neoplasms↗
PubMed1995

Children's head injuries in the Vietnamese refugee population in Hong Kong.

All Vietnamese patients with head injuries from two of the largest refugee camps in Hong Kong are routinely referred to the Neurosurgical Unit of the Prince of Wales Hospital for management. In order to determine the epidemiology of head injuries in this population group, we have retrospectively reviewed all hospitalized cases over a 4 year period from January 1990 to December 1993. We have found a unique social situation in this population group, with an unusually high proportion of paediatric cases (2253 per 100,000 children aged 5 years or less), compared with other epidemiological studies. The most common mechanism of injury in between 57 and 75 per cent of cases was a fall from bed. Based on this information, appropriate preventive measures have been recommended and have successfully decreased the incidence of head injuries. This study demonstrates the value and effectiveness of epidemiological studies in identifying a previously unrecognized health risk in a specified population group.

Age Factors↗
PubMed1995

Sinus histiocytosis with massive lymphadenopathy localized to the sella.

Sinus histiocytosis with massive lymphadenopathy (SHML) is a condition of unknown aetiology characterized by proliferation of histiocytes and lymphocytes, with the former phagocytosing the latter producing a typical histological appearance. Although first described in lymph nodes, cases have been reported in many extranodal sites, including the central nervous system. We report a case of SHML involving the sella turcica producing diabetes inspidus and pituitary dysfunction.

Adult↗
PubMed1995

Combined molecular genetic studies of chromosome 22q and the neurofibromatosis type 2 gene in central nervous system tumors.

Monosomy of chromosome 22 or deletions of 22q have been described in meningiomas and astrocytic tumors, the incidence of which is increased in Type 2 neurofibromatosis. Recently, the gene for neurofibromatosis Type 2 (NF2) has been identified at Chromosome 22q12, and a tumor suppression role has been suggested. Because there have been only a few studies of the NF2 gene on central nervous system tumors other than vestibular schwannomas, we investigated the potential role of NF2 as a tumor suppressor gene in a group of sporadic meningiomas and astrocytomas. Forty-four tumors (26 meningiomas and 18 astrocytic tumors of different grades) were screened for NF2 mutations for the entire 17 exons by the polymerase chain reaction-single-strand conformation polymorphism method. In addition, 37 tumors and their respective constitutional deoxyribonucleic acid were analyzed for loss of heterozygosity of 22q alleles by four polymorphic microsatellite markers. Seven inactivating mutations were found in Exons 4, 5, 6, and 10 in 7 of 26 (27%) meningiomas, but none were found in astrocytic tumors. Altogether, 69% of meningiomas and 20% of astrocytic tumors revealed a loss of heterozygosity of 22q markers. All tumors with NF2 mutations showed concurrent loss of alleles on 22q, thus fulfilling Knudson's criteria for tumor suppressor genes in meningiomas. We conclude that inactivation of the NF2 gene is involved in the pathogenesis of a proportion of meningiomas but not in astrocytic tumors. Because many meningiomas and some astrocytic tumors had allelic loss of 22q but intact NF2, there is a possibility that other tumor suppressor genes exist on 22q and may be involved in the pathogenesis of central nervous system tumors.

Adolescent↗
PubMed1995

Detection and assessment of intracranial aneurysms: value of CT angiography with shaded-surface display.

OBJECTIVE: The purpose of this study was to evaluate the efficacy of circle of Willis CT angiography with shaded-surface display in the detection and assessment of suspected intracranial aneurysms. MATERIALS AND METHODS: Twenty-three patients who had clinical or radiologic suspicion of intracranial aneurysms were studied prospectively with CT angiography and conventional angiography. The images were obtained and interpreted in a double-blind fashion by different radiologists. Conventional angiography, which was the reference standard in this study, diagnosed 17 aneurysms in 15 patients. The usefulness of the two types of images for surgical planning was evaluated by two neurosurgeons. RESULTS: No aneurysms were detected with either technique in eight patients. Both techniques showed 15 aneurysms in 14 patients. The maximum dimensions were less than 3.0 mm in three cases, 3.0-5.0 mm in four cases, and greater than 5.0 mm in eight cases. With conventional angiography used as the reference standard, CT angiography has one false-positive and two false-negative findings, resulting in a sensitivity of 88% (15/17) and a specificity of 89% (8/9). For 12 of 15 aneurysms, CT angiography was rated equal or superior to conventional angiography in depicting all aspects (shape, orientation, neck, and parent vessel) of the aneurysms. CONCLUSION: We were able to detect aneurysms of the circle of Willis as small as 2 mm in size. Using conventional angiography as the reference standard, CT angiography has a sensitivity of 88% and a specificity of 89% for the detection of aneurysms in the circle of Willis. In almost all cases, CT angiography was equal or superior to conventional angiography in characterizing the aneurysms for surgical planning.

Adolescent↗
PubMed1994

Polar spongioblastoma with cerebrospinal fluid metastases.

We presented a rare case of polar spongioblastoma occurring in a 12-year-old boy with cerebrospinal fluid (CSF) spread in the basal cisterns and contralateral ventricle, as well as metastases to the spinal dura. Apart from the typical palisades of elongated cells, immunohistochemically, the tumor cells stained for neuron-specific enolase and synaptophysin, and ultrastructural examination revealed features of neuronal differentiation. Our case adds to the small number of cases of polar spongioblastoma with clinicopathologic features and ultrastructural appearance described and confirms the neuronal nature of the tumor. It also represents the second documented case with CSF metastases.

Brain Neoplasms↗
PubMed1994

Adenoid formation in medulloblastoma: a case report.

A medulloblastoma in a 3-year-old girl was described that showed epithelial features in the form of adenoid or acinar structure. Ultrastructurally, these adenoid formations exhibited glandular features and immunohistochemically stained for cytokeratin. Such structures were interpreted to be a distinct and hitherto unreported form of epithelial differentiation in medulloblastoma, similar to other epithelial features described in rare cases of high grade astrocytomas.

Cerebellar Neoplasms↗
PubMed1994

The pathological spectrum of diffuse axonal injury in blunt head trauma: assessment with axon and myelin strains.

Although diffuse axonal injury (DAI) has been described as a major form of primary damage to the brain in blunt head injury, there has been no systematic study of the pathological changes in different regions of the brain. In this study, 22 cases of DAI were comprehensively examined histologically in the following areas: corpus callosum, internal capsule, superior cerebellar peduncles, cerebral white matter, fornix, rostral brain stem and globus pallidus, with a total of 17 standard blocks in each case. Sections were stained for axons with Glees and Marsland and neurofilament immunostaining and myelin with luxol fast blue and myelin basic protein immunostaining, and axonal retraction balls and myelin globoids were counted. Neurofilament immunostaining was superior to Glees and Marsland in both the positivity rates and the actual scores. Small myelin globoids were identified by the myelin stains, probably as a form of myelin damage secondary to axonal disruption. Such acute myelin damage was previously undescribed. There was no significant difference in both positivity rates and the scores obtained for luxol fast blue and myelin basic protein. Of all the regions of the brain examined, the internal capsule, corpus callosum and superior cerebellar peduncles yielded the highest counts of axonal balls as well as the highest incidences. It is recommended that in cases of DAI, these three regions of the brain should be examined most profitably with neurofilament immunostaining supplemented with a myelin stain.

Adolescent↗
PubMed1994

Paraffin section p53 protein immunohistochemistry in neuroectodermal tumors.

In an attempt to characterize the role of p53 alterations in the pathogenesis of intracranial neuroectodermal tumors, 196 tumors were immunostained with a monoclonal antibody against the p53 protein on archival materials of formalin-fixed, paraffin-embedded materials. Only 11% of well differentiated astrocytomas stained positive, whereas up to 40% of high-grade astrocytomas (anaplastic astrocytomas and glioblastoma multiforme) were immunolabelled. The extent of immunolabelling of tumor cells also increased from the low-grade to high-grade astrocytomas. Among the high-grade astrocytomas, the small anaplastic cells were the predominant cell type which exhibited aberrant p53 protein accumulation. Rare cases of oligodendrogliomas and medulloblastomas also stained positive, whereas ependymomas and choroid plexus tumors were uniformly negative. p53 alterations therefore appear to play a role in the progression from low-grade to high-grade astrocytomas and the cell type which appeared to be critically involved appeared to be the small anaplastic cells.

Astrocytoma↗
PubMed1994

An anterior intradural neurenteric cyst of the cervical spine: complete excision through central corpectomy approach--case report.

The case of a cervical intraspinal neurenteric cyst in a 6-year-old boy is reported. The anterior intradural location of the cyst was confirmed by preoperative magnetic resonance imaging. Complete excision of the cyst was achieved through the anterior central corpectomy approach. The vertebral defect was reconstructed with autogenous fibular graft. The child made a complete neurological recovery without a mechanical problem either at the neck or at the graft donor site.

Bone Transplantation↗
PubMed1993

Successful treatment of amoebic meningoencephalitis in a Chinese living in Hong Kong.

Primary amoebic meningoencephalitis due to Naegleria fowleri was found in a 38-year-old Chinese man living in Hong Kong who presumably acquired the infection from swimming in a hot spring in neighbouring China. Amoebic cysts were identified in tissue taken from a brain abscess. The patient responded to surgical drainage and a 6-week course of amphotericin B, rifampicin and chloramphenicol. This is one of 6 cases of successful treatment of primary amoebic meningoencephalitis documented in the medical literature.

Adult↗
PubMed1993

Effect of intravenous ketanserin on arterial and intracranial pressures in patients with systemic hypertension following intracerebral haemorrhage.

The response of arterial BP and intracranial pressure to an intravenous injection of the serotonin antagonist, ketanserin, was recorded in ten patients with hypertension following intracerebral haemorrhage. Five minutes after ketanserin administration, arterial pressure had fallen by 40/21 mmHg from a baseline level of 213/113 mmHg, and remained below pre-treatment levels for two hours. Intracranial pressure was steady throughout the two hour observation period. Although calculated cerebral perfusion pressures declined and whereas it is not known if cerebral perfusion might have been compromised in zones of borderline ischaemia, the present data suggest that ketanserin might be preferred to drugs known to raise intracranial pressure or agents requiring infusion and intensive haemodynamic monitoring for patients with severe hypertension complicating intracerebral haemorrhage.

Blood Pressure↗