Biomedical subjects
Publications and source records attributed to W S Poon.
The impact of teleradiology technology used in the management of neurosurgical emergencies between district general hospitals and tertiary neurosurgical centres is reviewed. Its effect on clinical management such as diagnostic accuracy and the prevention of secondary insults has been shown to be favourable. Problems and possible future developments are also discussed.
A 67-year-old man presented with actinomycotic osteomyelitis of the skull and underlying central nervous system (CNS) involvement. The computed tomography (CT) and magnetic resonance imaging (MRI) findings are discussed and the radiological literature is reviewed.
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Free radicals are generated after head injury. These radicals rapidly react with polyunsaturated fatty acids in the cell membrane and cause membrane destruction. This process is called lipid peroxidation. Malondialdehyde (MDA) is one of the end products of lipid peroxidation, and it is a frequently used indicator of lipid peroxidation in biological tissues. Using a diffuse head injury animal model, we studied the time course of lipid peroxidation in different regions of injured rat brains. In the present study, the MDA levels were 36.7%, 41.8%, and 35.1% greater than sham at one hour after injury at the frontal, parietal, and brain stem, respectively (p < 0.0001). The MDA levels in these regions continued to increase and peaked a 4 hours after the injury. The levels slowly decreased, and by 24 hours, they were still significantly higher than the sham control's. The elevation of MDA levels was less in the striatum and the temporal regions at one hour. They were 16.9% and 13.3%, respectively (p < 0.002). The MDA levels in these two regions continued to increase even after 4 hours of injury, but the degree of elevation never exceeded 35%. The results demonstrate that there is an immediate, posttraumatic burst of MDA production, suggesting the formation of free radicals after diffuse head injury. Even though all the regions sampled show the same effect, certain regions are less affected by this diffuse head injury animal model.
Abnormalities of chromosome 22q have been well studied as a major molecular genetic event in meningiomas. Chromosome 14q loss has also been shown to be a common phenomenon. However, only a few studies have reported molecular genetic changes of this chromosome in meningioma. In this study, we examined 41 sporadic meningiomas of different histological subtypes and grades with 15 polymorphic microsatellite markers covering a wide region on chromosome 14q. Overall, 37% (15 of 41) of cases showed loss of heterozygosity for one or more allelic markers. Thirty percent (10 of 33) of benign tumors showed allelic losses, whereas 62.5% (5 of 8) of high-grade meningiomas showed loss of heterozygosity. There were altogether eight cases of partial deletions and seven cases of probable monosomy of 14q. Allelic losses of 14q were also commonly seen in recurrent tumors (3 of 3, 100%), parasagittal tumors (4 of 7, 57%), and tumors with transitional subtype (7 of 14, 50%). Among the tumors with allelic losses of 14q, all except one concurrently showed loss of heterozygosity for markers on 22q by our previous study. Of the eight cases with partial deletions, one showed losses on 14q11.1-31, two showed deletions on 14q24.3-31, three showed losses at 14q32.1-32.2, and the remaining two showed deletions at 14q24.3-32.2. We therefore defined two cluster regions of deletion on chromosome 14q: 14q24.3-31 and 14q32.1-32.2. Our studies suggested that more than one tumor suppressor gene(s) residing on distinct regions of chromosome 14q are important in the development and atypical or anaplastic changes in meningiomas.
OBJECTIVE: In many countries, neurosurgical care is concentrated in regional centres, which often necessitates the inter-hospital transfer of patients with head injury for optimal treatment. The aim of this study was to evaluate the role of teleradiology in the management of head-injured patients when-referred from a district general hospital to a tertiary neurosurgical centre. METHODS: Prospective data were collected over a fifteen month period from March '95 to May '96. Head-injured patients referred without the facility of teleradiology (Group 1), were compared to similar patients referred with teleradiologic images (Group 2), with particular regard to therapeutic intervention before transfer and adverse events during transfer. RESULTS: There were 28 patients in Group 1 and 35 in Group 2, of which 31 were transferred. Both groups were comparable with respect to age, admission Glasgow Coma Scale score, and intracranial pathology. For patients transferred with teleradiology consultation (Group 2), therapeutic interventions were more (32.1% vs. 10.7%, p = 0.06), adverse events during transfer were significantly lower (6.4% vs. 32.1%, p = 0.01), and transfer time was reduced (72 vs. 80 minutes, p = 0.38). Four patients in Group 2 were treated by a mobile neurosurgical team at the referring hospital because of rapid clinical deterioration. CONCLUSION: Our findings indicate that teleradiology has an important role in improving inter-hospital management of head-injured patients.
The aim of this study was to examine the role of teleradiology in the management of inter-hospital transfer of neurosurgical patients, especially in terms of safety and early therapeutic interventions. Data were collected prospectively, comparing events during the inter-hospital transfer of patients from a district general hospital to a tertiary neurosurgical centre, before and after teleradiology became available. From March to December 1995, 50 referrals made without teleradiology were compared with 66 referrals after teleradiology installation. Our results showed that for patients referred with teleradiologic images, unnecessary transfers were reduced (21%), more therapeutic measures before transfer were implemented (27% vs 20%, p = 0.41), adverse events occurring during transfer were significantly reduced (8% vs 32%, p = 0.002), and transfer time was shortened (72 min vs 80 min, p = 0.38). The potential advantages of this system in facilitating safer transfers and faster management of neurosurgical emergencies therefore merit further attention.
Cerebellar hemangioblastoma is one of the most frequent manifestations of the autosomal dominantly inherited von Hippel-Lindau (VHL) disease but also may manifest as a sporadic tumor. The purpose of this study was to define the alterations of the VHL gene in hemangioblastomas. We analyzed nine specimens from eight cerebellar hemangioblastomas (three familial and five sporadic) and six blood samples from family members of two unrelated pedigrees for mutations of the VHL gene using single-strand conformation polymorphism analysis and direct sequencing. We identified germline mutations in all VHL-associated tumors and somatic mutations in two (40%) of five sporadic hemangioblastomas. We also observed germline mutations in the peripheral blood DNA from members of two unrelated families; one is currently without VHL manifestations, and the other is affected. In addition, loss of heterozygosity of allelic markers on chromosome 3p were examined by four polymorphic microsatellite markers, and aberrant methylation of the VHL gene was investigated with a methylation-sensitive enzyme, Sma I. Allelic losses on chromosome 3p were observed from two patients with VHL disease in one family and in one of two sporadic hemangioblastomas. No hypermethylation of the VHL gene was detected in any of the tumors that we examined. Our findings suggest that the VHL tumor suppressor gene is the target for inactivation in this tumor and is involved in the pathogenesis of familial and sporadic hemangioblastomas.
OBJECTIVE: Primary brain tumours may be associated with coagulation disorders which can pose intraoperative and postoperative management difficulties. The aim was to evaluate the coagulation profile of patients with brain tumours undergoing surgery using thromboelastography (TEG) in combination with simple laboratory tests. METHODS: Fifty adult patients with primary brain tumours larger than 4 cm in maximum diameter and no history of coagulation disorders were studied in a prospective, observational manner over a one year period. Preoperative, intraoperative, and postoperative measurements included haemoglobin concentration, platelet count, prothrombin and partial thromboplastin times, fibrin(ogen) degradation product concentration, D-dimer concentration, and TEG. RESULTS: Eleven patients (22%) had abnormal intraoperative TEGs, of whom six (12%) subsequently developed haematomas requiring surgical evacuation. The coagulopathy seemed to be hyperfibrinolysis in two cases (4%) and disseminated intravascular coagulation in four (8%). There was no preoperative difference in reaction time (R time) for clot formation between the non-haematoma and haematoma groups(mean 11.44 (SD 3.42) v 12.33 (2.50) min, P=0.46). However, when other preoperative indices were compared, in the non-haematoma group, K time (time to reach a clot amplitude of 20 mm) was shorter (6.72 (2.15) v 10.56 (3.50) min, P=0.001), rate of clot growth (å) was faster (43.67 degrees (7.53) v 27.11 degrees (5.42), P<0.0001) and maximum amplitude of clot strength (MA) was greater (52.64 (7.85) v 40.33 (6.59) mm, P<0.001). Intraoperatively, R time was significantly shortened in the non-haematoma group, (7.67 (1.78) min, P<0.0001) unlike the haematoma group (10.67 (1.58) minutes, P=0.11). CONCLUSIONS: Although these results indicate a general hypercoagulability during brain tumour surgery, in certain cases, a predisposition towards hypocoagulability may exist even before surgery, detectable only when the physical characteristics of clot formation are studied by TEG. Judicious replacement of clotting factors, platelets, and antifibrinolytic agents should be considered intraoperatively if the TEG is abnormal, without waiting for laboratory test results.
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BACKGROUND AND PURPOSE: In spontaneous intracerebral hemorrhage (ICH), the site, age of the patients, and preexisting hypertension are important factors in determining the possibility of finding an underlying vascular abnormality by cerebral angiography. To what extent these three factors affect the indication for angiography remains controversial. A prospective study was carried out to correlate the angiographic findings with these three factors. METHODS: Two hundred six consecutive spontaneous ICH cases with an age range from 5 to 79 years (median, 45) were investigated with CT and cerebral angiography over a 3-year period (April 1993 through March 1996). Exclusion criteria were (1) poor surgical risk or severely neurologically disabled patients, (2) refusal of angiography, (3) patients in whom severe coagulopathy accounted for the hemorrhage, (4) bleeding into tumor, or (5) subarachnoid hemorrhage-predominant cases. RESULTS: Angiographic yield (the frequency of positive angiography in a defined patient group) was significantly higher in patients (1) at or below the median age of 45 than those above (53/105, 50%, versus 18/101, 18%; P < .001) and (2) without preexisting hypertension than those with (64/145, 44%, versus 5/58, 9%; P < .001). The correlation of age and preexisting hypertension to angiographic yield was independent (logistic regression coefficients -0.056 and -1.59 and SE 0.12 and 0.515, respectively, both P < .001). In patients of the younger age group without preexisting hypertension, angiographic yield was 48% in putaminal, thalamic, or posterior fossa ICH and 65% in lobar ICH. In the older hypertensive patients, the yields were 0% and 10%, respectively. However, in patients with isolated intraventricular hemorrhage, most were normotensive and the yield was high in both age groups (67% versus 63%). CONCLUSION: Diagnostic cerebral angiography should be considered for all spontaneous ICH patients except those over 45 years old with preexisting hypertension in thalamic, putaminal, or posterior fossa hemorrhage.
The authors studied 31 comatose head-injured patients to assess the clinical usefulness of laser Doppler flowmetry (LDF) in continuous autoregulation monitoring. The LDF probes were placed on the surface of the cerebral cortex. Data on LDF, intracranial pressure (ICP), and arterial blood pressure (ABP) were recorded and continuously entered into a computer. The data were broken down into multiple segments of 15 minutes' duration (epochs). Epochs showing rapid change in cerebral perfusion pressure (CPP), change in CPP of less than 10 mm Hg, LDF values of less than five arbitrary units, and loss of ABP/ICP waveform were excluded from further analysis. A linear relationship between LDF and CPP in individual epochs was used as an indicator of loss of autoregulation. The relationship between LDF and CPP changed with time, indicating improvement or deterioration in autoregulation. Longitudinal analysis of all the epochs measured in a patient revealed three patterns of progress: 1) intact autoregulation; 2) transient loss; and 3) persistent loss of autoregulation. All five patients with intact autoregulation had a good outcome. Ten patients experienced transient loss of autoregulation; of these four had a good outcome, five were moderately disabled and one was severely disabled. Transient impairment of autoregulation did not always indicate poor outcome, provided the impaired autoregulation responded to treatment. In 11 patients who had persistent loss of autoregulation, nine died and two were severely disabled. In five cases the LDF probe lost contact with the cerebral cortex and no useful information was obtained. Real-time measurement of autoregulation using LDF and CPP monitors was achieved and the findings were related to outcome in these patients.
The generally accepted definition of mild head injury includes Glasgow Coma Scale (GCS) scores of 13 to 15. However, many studies have shown that there is a heterogeneous pathophysiology among patients with GCS scores in this range. The current definition of mild head injury is misleading because patients classified in this category can have severe sequelae. Therefore, a prospective study of 1360 head-injured patients with GCS scores ranging from 13 to 15 who were admitted to the neurosurgery service during 1994 and 1995 was undertaken to modify the current definition of mild head injury. Data regarding patients' age, sex, GCS score, radiographic findings, neurosurgical intervention, and 6-month outcome were collected and analyzed. The results of this study showed that patients with lower GCS scores tended to have suffered more serious injury. There was a statistically significant trend across GCS scores for percentage of patients with positive acute radiographic findings, percentage receiving neurosurgical interventions, and percentage with poor outcome. The presence of postinjury vomiting did not correlate with findings of acute radiographic abnormalities. Based on the results of this study, the authors divided all head-injured patients with GCS scores ranging from 13 to 15 into mild head injury and high-risk mild head injury groups. Mild head injury is defined as a GCS score of 15 without acute radiographic abnormalities, whereas high-risk mild head injury is defined as GCS scores of 13 or 14, or a GCS score of 15 with acute radiographic abnormalities. This more precise definition of mild head injury is simple to use and may help avoid the confusion caused by the current classification.
The incidence of complications associated with cerebrospinal fluid shunt procedures varies from low to high in different series and depending on the duration of follow up. We report an unusual case of four-month-old male infant with hydrocephalus who developed bilateral hydroceles soon after ventriculoperitioneal shunting. The possible aetiology is hypothesised and suggestions are made as to how this may be avoided in other infants undergoing shunt procedures.
A 72-year-man with previous lead poisoning presented with raised intracranial pressure and localizing neurologic signs. CT scans showed a high-grade glioma and extensive intracranial calcifications, which proved to be vascular in distribution on postmortem examination. The latter findings support the concept of dystrophic calcification following lead-induced cerebrovascular injury. Lead poisoning should be considered in the differential diagnosis of unexplained intracranial calcifications. There is also evidence from previous studies to suggest a causative relationship between lead poisoning and development of glioma.
Cloverleaf skull or kleeblattschadel usually occurs as a result of premature closure of the cranial sutures, with accompanying hydrocephalus, proptosis, cranial base and midface hypoplasia. The incidence of this abnormality is rare, with less than 130 reported cases in the literature, and is associated with various congenital syndromes. Conventional surgical management advocates shunting prior to definitive craniotomy and bone remodeling. We report an unusual case of Pfeiffer syndrome with associated cloverleaf skull deformity, in which early surgery was vital for decompression of raised intracranial pressure and shunt independence for the first six months. A secondary craniofacial procedure was performed at nine months of age to improve cosmesis. In such cases, good outcome can be achieved if aggressive surgery is combined with good paediatric anaesthesia and intensive care.
Head injury in children causes special concern in most communities. From 1989 to 1994, 2,785 children younger than 16 years old were admitted to our neurosurgical service because of head injury. Fall from a height was the major cause of head injury leading to admission in infants and children in preschool age groups, whereas traffic-related or bicycle-related accidents were more likely to be the cause of head injury for those aged 11-15 years. In all age groups there was a male preponderance. The overall mortality was 0.6%. Traffic-related accidents caused more severe injury and accounted for 67% of all fatalities. For patients under 6 years old, about 40% of head injuries occurred at home. Preventive measures for pediatric head injury in Hong Kong are suggested.
A prospective observational study of the pathophysiology of sodium and water disorders in patients with pituitary region tumours after surgical excision was carried out in 20 patients. Serial pre-operative and post-operative fluid and sodium balance, plasma and urine elctrolyte biochemistry and their derived parameters, and circulating hormones associated with fluid balance, atrial natriureic peptide (ANP) and antidiuretic hormone (ADH) were documented to correlate with the patients' clinical conditions. Ten out of these twenty cases developed diabetes insipidus (DI) requiring ADH replacement therapy, although in the majority (6 cases), this way only a transient event. Of the nine patients who developed hyponatraemia, six had symptoms such as impaired consciousness and convulsions. Four patients developed alternating hypoatraemia and hypernatraemia, which constituted a difficult group, where appropriate sodium and fluid management, and ADH replacement therapy were based upon twice daily plasma and urine biochemistry and their derived parameters. Whilst DI in this group of patients was the result of a low circulating ADH level, hyponatraemia was not associated with an exaggerated ADH activity (6.0 +/- 2.3 vs 7.4 +/- 2.3 pmol/ml, mean +/- SEM). Rather, hyponatraemia was strongly associated with an elevated circulating ANP concentration (82.4 +/- 10.5 vs 30.0 +/- 3.1 pmol/ml, mean +/- SEM, p < 0.001), resulting in salt wasting and hypovolaemia.