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Biomedical subjects

W S Poon

Publications and source records attributed to W S Poon.

144 records · Page 8Linked to original sources
PubMed1992

Assessment of the twin impinger for size measurement of metered-dose inhaler sprays.

The calibration of the first stage of the twin-stage impinger, an instrument proposed for use in measuring the spray size from metered-dose inhalers, was performed with monodisperse aerosols by a standard technique for cascade impactors. The mean cut point was found to be not particularly sensitive to operating variables which may be expected to occur in practice. The cut point was close to that reported previously, although the collection efficiency curve was found to be slightly sharper. Calculations are reported on the expected results of measurements on aerosols in a two-stage instrument with an idealized perfect collection efficiency curve as well as the curve measured for the twin impinger. These results indicate that important characteristics of spray size distribution cannot be distinguished with an ideal two-stage instrument; the twin impinger is less capable than an ideal instrument.

Aerosols↗
PubMed1992

Basal ganglia teratomas: report of three cases.

Three cases of intracranial teratomas occurring at the basal ganglia of three young male patients were reported. Their radiologic appearances closely resembled each other with multicystic tumor masses located deep in the basal ganglia. Histology showed teratocarcinoma, combined immature teratoma and germinoma, and teratoma with malignant transformation. These tumours represent a distinct clinico-radiologic group of lesions and serve as an addition to the dearth of information reported about the histological subtypes of intracranial teratomas.

Adult↗
PubMed1992

Hospital arrival time after onset of stroke.

To estimate the proportion of patients with stroke likely to be eligible for a trial of anticoagulant treatment for acute ischaemic stroke, the interval between onset of symptoms and arrival at hospital was analysed prospectively. Of 773 patients with stroke admitted in one year, 63% arrived at hospital within 12 hours, 76% within 24 hours, and 85% within 48 hours of ictus. The arrival time varied significantly with stroke subtype. Patients with intracerebral haemorrhage tended to arrive earlier than those with cerebral infarct, who arrived sooner than those with lacunar infarct. The results suggest that about half of all patients with ischaemic stroke in Hong Kong would present within 12 hours of ictus, in time for inclusion in a therapeutic trial.

Aged↗
PubMed1992

Laser-induced fluorescence: experimental intraoperative delineation of tumor resection margins.

The ability of laser-induced fluorescence spectroscopy to delineate tumor margins intraoperatively was studied using a rat intracerebral glioma model. A fluorescent dye, chloro-aluminum phthalocyanine tetrasulfonate (ClAlPcS4), was injected intravenously 24 hours before tumor resection. The animals underwent tumor resection under the operating microscope, guided by laser-induced fluorescence measurement in one group (Group 1) and visual assessment in the other (Group 2). The Group 1 rats had a significantly reduced volume of residual tumor following resection (0.5 +/- 0.2 cu mm vs. 13.7 +/- 4.0 cu mm, mean +/- standard error of the mean, p less than 0.02). Three of the nine animals in Group 1 were tumor-free at 2 weeks following resection, compared with none of the 10 rats in Group 2 (p less than 0.05). Interference from brain autofluorescence was minimized using spectrally resolved detection and the ClAlPcS4 dye, which has a 680-nm fluorescence peak significantly higher than the 470-nm autofluorescence peak of normal brain. Contrast ratios of up to 40:1 were found for glioma:normal brain fluorescence signals. Spatially-resolved spectra were acquired in approximately 5 seconds using a fiberoptic probe. This study demonstrates the ability of an intraoperative laser-induced fluorescence system to detect tumor margins that could not be identified with the operating microscope.

Animals↗
PubMed1992

Traumatic extradural hematoma of delayed onset is not a rarity.

During a 4.5-year period, 73 patients with traumatic extradural hematoma (EDH) were admitted to the neurosurgical unit of the same hospital and managed with surgical evacuation. Of these consecutive admissions, 22 patients with delayed EDH are reported. The incidence of this condition (30%; 22 of 73) contrasts with reports in the literature of 0 to 10%. This may be related to the availability of computed tomography and its liberal and early use in all head injuries. The overall mortality of traumatic EDH (5%; 4 of 73) was related to cases of delayed onset EDH. In addition to a high index of suspicion, early diagnosis of delayed EDH can be facilitated by liberal use of intracranial pressure monitoring and serial computed tomography.

Adult↗
PubMed1991

Comparison of management outcome of primary and secondary referred patients with traumatic extradural haematoma in a neurosurgical unit.

A total of 104 patients with a traumatic extradural haematoma in a 5-year period were studied. The mortality of the 71 patients managed primarily by the neurosurgical unit was less than that of the 33 patients secondarily transferred from the district general hospital: 4 per cent vs 24 per cent. This better result was associated with a shorter delay between the time of conscious level deterioration and decompressive operation: 0.7 +/- 1.0 h vs 3.2 +/- 0.5 h. Direct admission of all head injured patients to a neurosurgical unit resulted in significant reduction in mortality and morbidity in patients with an extradural haematoma.

Adolescent↗
PubMed1990

Gliosarcoma of the posterior fossa with features of a malignant fibrous histiocytoma.

A rare case of gliosarcoma occurring in the posterior fossa of a 62-year-old man is reported. Histologically, the tumor closely resembled that of a typical case of malignant fibrous histiocytoma (MFH). Such features have not been reported previously in gliosarcoma. The importance of using an immunoperoxidase preparation against the glial fibrillary acidic protein (GFAP) in diagnosing gliosarcoma is emphasized. Our case also lends support to the contention that MFH-like histologic features may occur in poorly differentiated neoplasms of diverse origins.

Brain Neoplasms↗
PubMed1990

Accuracy of different routes of intracranial pressure (ICP) monitoring using microtransducers.

Intracranial pressure (ICP) monitoring using microtransducer and intraventricular pressure (IVP) was compared simultaneously in 20 consecutive head-injured patients within a 1-year period. In the first four patients with subdurally placed transducers, an acceptable corresponding rate with IVP was demonstrated (88%). In the remaining 16 patients with extradurally placed transducers, acceptable accuracy (73%) was only achieved in the last four. This accuracy was repeated in an additional six patients with extradurally placed transducers (75% corresponding with IVP). We have therefore suggested that, before extradural pressure monitoring can be employed alone in clinical practice, a comparison with IVP should be performed.

Journal Article↗
PubMed1990

Primary germinoma of the posterior fossa with CSF and extracranial metastases.

We describe the case of a 1-year-old boy presenting clinically and radiologically with a haematoma occurring in the cerebellum. Histological examination revealed a germ cell tumour with a pure germinomatous component. The patient subsequently succumbed with extensive tumour metastases in the spinal cord and the subcutaneous tissues of the scalp. This represents the first comprehensive documented report of a germinoma arising in the posterior fossa.

Cerebellar Neoplasms↗
PubMed1989

Secretion of antidiuretic hormone in neurosurgical patients: appropriate or inappropriate?

In neurosurgical patients with hyponatraemia (plasma sodium less than 130 mmol/l) and natriuresis, increased antidiuretic hormone (ADH) secretion may be appropriate rather than inappropriate. Ten such patients were studied prospectively to assess circulating ADH concentration and body fluid volumes. Compared with a control group, the mean plasma ADH level was significantly elevated (0.9 pmol/l (s.e.m. = 0.2) versus 0.2 pmol/l (s.e.m. = 0.1], the total body water was normal (101% (s.e.m. = 3) versus 100% (s.e.m. = 6], while the blood volume was significantly reduced (89% (s.e.m. = 3) versus 104% (s.e.m. = 5]. The elevated ADH level was therefore appropriate to a reduced blood volume. This suggests that, in neurosurgical patients with hyponatraemia, fluid restriction could be dangerous. Serial observations in this small group of patients showed that salt replacement and normal fluid intake resulted in a fall in the elevated ADH levels.

Acute Disease↗
PubMed1988

Intracranial olfactory neuroblastoma mimicking carcinoma: report of two cases.

Two cases of olfactory neuroblastoma which presented clinically as intracranial lesions are described. Prominent features of epithelial differentiation were present, which led to initial diagnoses of poorly differentiated carcinoma. The true nature of the lesions was only established subsequently by careful histological examination, immunohistochemistry and electron microscopy. The potential towards epithelial differentiation in such tumours was emphasized and certain new histological features were described, including a biphasic epithelial and stromal pattern, papillae formation and positive staining for cytokeratin. These two cases underline the importance of exhaustive examination of poorly differentiated epithelial-like lesions of the frontal lobes by conventional histology, immunohistochemistry and electron microscopy.

Brain Neoplasms↗
PubMed1988

Tumours of the central nervous system in Chinese in Hong Kong: a histological review.

One hundred and sixty-eight cases of tumours of the central nervous system (CNS) from Chinese patients in Hong Kong were reviewed histologically as well as by the immunoperoxidase techniques in equivocal cases. Detailed comparisons were made between this series and previously published series on CNS tumours in Chinese, in other Asians and in Caucasians. The percentage of gliomas was low, and the average age of patients with high grade astrocytomas was low. Meningiomas were relatively common tumours and microcystic meningiomas were a common histological subtype. The percentages of vascular malformations and haemangioblastomas were also higher than those recorded in the West. The difference in incidence in gliomas and vascular malformations between this series and previous reports from mainland China was attributed to a possible difference between southern and northern Chinese.

Astrocytoma↗
PubMed1988

Trichinosis diagnosed by computed tomography.

Trichinosis is a worldwide disease contained by good husbandry and culinary practice, presenting unexpectedly in individual cases or mini-epidemics. The disease varies greatly in its manifestation and severity although when marked can be recognized by fever with myositis and periorbital oedema. Antibody tests are specific but the appearance on computed tomography of the brain are sufficiently characteristic to allow a confident diagnosis. Two cases where such appearances led to the diagnosis are reported.

Adult↗
PubMed1988

Primary cerebral T-cell lymphoma: a case report.

A case of a 16-year-old boy with a rapidly progressive primary cerebral pleormorphic lymphoma of the brain is reported. Immunostaining with a panel of antibodies confirmed the T-cell lineage of the tumour. This is apparently the first documented report of primary T-cell lymphoma of the central nervous system.

Adolescent↗
PubMed1982

Haemorrhage from pelvic fractures: dangers and treatment.

A simple, non-invasive method of control of haemorrhage from severe fractures of the pelvis is described. This method is the application of a pneumatic splint from the costal margin to the toes; the splint is then inflated to a pressure of 30 cm of water. The splint was originally designed for the control of leaking aortic aneurysms. We have applied it to 4 patients with severe fractures of the pelvis. There was dramatic improvement in 2 of these patients in whom the bleeding had continued in spite of energetic initial resuscitation.

Accidents, Traffic↗
PubMedDate not supplied

Is routine computed tomographic (CT) scanning necessary in suspected basal skull fractures?

The aim of this prospective observational study was to assess the yield of routine fine-cut computed tomographic (CT) scans in patients with suspected basal skull injuries. Over an 8 month period in 1994, 500 consecutive head-injured patients were examined for clinical signs of basal skull fracture and underwent fine-cut (5 mm) CT scans through the skull base in addition to standard (10 mm) cuts through the vault. Clinical signs were present in 144 patients (144/500, 28.8 per cent) of which 75 (75/144, 52 per cent) had corresponding CT evidence of fracture. A further 22 patients (22/500, 4.4 per cent) had no clinical signs but fractures were seen on CT. The presence of cranial nerve injury, cerebrospinal fluid leak, epistaxis, periorbital bruising, and two or more signs, were more likely to be associated with positive CT scans (P < 0.001, chi 2 tests). The incidence of associated mass lesions was 50.5 per cent, of which 55.1 per cent required craniotomy. This was significantly higher than in patients without evidence of skull base fracture (16.6 per cent) (P < 0.001, chi 2 27.165). Six patients, two of whom had meningitis, required surgical repair of the dural defects seen on CT. The diagnostic yield of routine fine-cut CT scans in this sub-type of head injury is 52 per cent, and is of value in detecting associated mass lesions or significant dural defects which may require surgical intervention.

Adolescent↗