Biomedical subjects
Publications and source records attributed to Y W Fan.
Intramedullary schwannomas are rare spinal cord tumours. Correct preoperative diagnosis is essential for proper surgical planning and complete resection. We present a case of cervical intramedullary schwannoma followed by discussion on its preoperative magnetic resonance imaging features and review of the literature.
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AIM: The present study aimed to examine attentional deficits in patients with persisting post-concussive symptoms using a multi-componential framework of attention. DESIGN: A cross-sectional investigation using standardized tests and questionnaires of attention including 92 patients. METHOD: Participants were administered comprehensive measures of attention assessing sustained attention (Sustained Attention Response to Task, Backward Digit Span), selective attention (Stroop Word-Colour Test, Colour Trails Test), divided attention (Paced Auditory Serial Addition Test, Symbol Digit Modalities Test), and attentional control (Tower of Hanoi, Six Elements Test). Ecological tests of attention were used to validate the cluster solution. MAIN OUTCOME: Three clusters of patients with different combinations of attentional deficits were identified. They were 'mild sustained attentional deficits', 'selective and divided attentional deficits', and 'general attentional deficit'. A MANOVA indicated that these three clusters were statistically and clinically different from one another in terms of different attentional components proposed. CONCLUSION: This study provides preliminary evidence suggesting that sub-types of attentional impairments exit in patients with post-concussive symptoms.
A 34 year old Chinese man presented with grand mal seizures complicating multiple brain abscesses caused by mixed oral flora. Because of persistent hypoxaemia contrast spiral thoracic computed tomography was done, which revealed bilateral pulmonary arteriovenous malformations (PAVMs). Concomitant IgA and IgG subclass deficiency was also found. The combination of these two conditions appears to have predisposed this patient to presumably paradoxical septic embolism. The patient's cerebral condition responded to postoperative antibiotic treatment and he eventually received selective coil embolisation of right lower lobe PAVMs, which relieved his hypoxaemia and dyspnoea.
The adherence and viability of central neural cells (substantia nigra) on a thin layer of SiO(2) on Si wafers with different surface roughness were investigated. Variable roughness of the Si wafer surface was achieved by etching. The nano-scale surface topography was evaluated by atomic force microscopy. The adherence and subsequent viability of the cells on the wafer were examined by scanning electron microscopy (SEM) and fluorescence immunostaining of tyrosine hydroxylase (TH). It is found that the surface roughness significantly affected cell adhesion and viability. Cells survived for over 5 days with normal morphology and expressed neuronal TH when grown on surfaces with an average roughness (Ra) ranging from 20 to 50 nm. However, cell adherence was adversely affected when surfaces with Ra less than 10 nm and rough surfaces with Ra above 70 nm were used as the substrate. Such a simple preparation procedure may provide a suitable interface surface for silicon-based devices and neurones or other living tissues.
Myxofibrosarcoma was originally described as the myxoid variant of malignant fibrous histiocytoma (MFH). It is uncommon in the head and neck region. We hereby report a case of myxofibrosarcoma in the sphenoid sinuses. The diagnostic and management difficulties are discussed. Close collaboration between surgeon, radiologist, histopathologist and clinical oncologist in makng accurate diagnosis and appropriate management of this rare tumour are emphasized.
Trans-sphenoidal removal of pituitary tumours using the endonasal endoscopic technique, a novel application, is herein reported in five consecutive patients with growth-hormone-secreting pituitary adenomas seen at a teaching hospital in Hong Kong. All five patients demonstrated complete tumour removal on postoperative imaging and hormonal assessment following the procedure. Surgical morbidity and symptoms were minimal; postoperative obstructive nasal packing was not required with this technique, which greatly improved patient comfort. Preliminary experience suggests that the endonasal endoscopic approach is a safe and effective alternative to the conventional trans-septal microscopic method for the treatment of pituitary tumour. A randomised controlled trial comparing these two approaches is currently underway at this institution.
We have previously reported high-frequency microsatellite instability (MSI-H) and germ-line mismatch repair gene mutation in patients with unusually young onset of high-grade glioma. Some of these patients developed metachronous MSI-H colorectal cancer and conformed to the diagnosis of Turcot's syndrome. Frameshift mutation of TGFbetaRII was present in all the colorectal carcinomas but not in brain tumours. We further characterized the genetic pathways of tumour evolution in these metachronous gliomas and colorectal carcinomas. All MSI-H glioblastomas had inactivation of both alleles of the p53 gene and showed over-expression of the p53 protein while none of the colorectal carcinomas had p53 mutation or protein over-expression. Flow cytometry and comparative genomic hybridization revealed that all glioblastomas were chromosomal unstable with aneuploid DNA content, and with a variable number of chromosomal arm aberrations. In contrast, the colorectal carcinomas had diploid or near-diploid DNA content with few chromosomal arm aberrations. The pattern of chromosomal aberrations in the two organs was different. Loss of 9p was consistently observed in all glioblastomas but not in colorectal carcinomas. Epidermal growth factor receptor amplification was absent in all glioblastomas and colorectal carcinomas. Our results suggest that both the frequency of p53 mutation and its effects differ greatly in the two organs. Following loss of mismatch repair function, p53 inactivation and chromosomal instability are not necessary for development of colorectal carcinoma, but are required for genesis of glioblastoma. Oncogene (2000) 19, 4079 - 4083.
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BACKGROUND: Aneurysms of the ophthalmic segment of the carotid artery are difficult lesions to handle. Batjer and Samson described the technique of suction decompression of the aneurysm by inserting a needle and aspirating blood from the internal carotid artery in the neck. However, this method carries a risk of arterial dissection and distal embolization. METHOD: We describe a revised technique for suction decompression of paraclinoid aneurysms. The method makes use of the anatomical advantage of the carotid bifurcation. Instead of direct clamping of the internal carotid artery, we isolated the common and external carotid arteries and decompressed the aneurysm via the external carotid artery. We also saved the aspirated blood for autotransfusion. RESULTS: We have used this technique in two elderly patients with good results. CONCLUSION: This technique avoids dissection of the internal carotid artery and minimizes the risk of embolization.
Tuberculous infection of the central nervous system is common in Hong Kong. A 39-year-old woman presented with isolated right sixth nerve palsy which was non-progressive for 10 months. Neuro-imaging revealed a right pontine lesion. Cerebrospinal fluid (CSF) examination showed lymphocytic meningitis with negative bacteriological and cytological studies. Empirical antituberculous drugs with initial corticosteroid resulted in improved CSF parameters. A diagnosis of cerebral tuberculoma complicated by meningitis was made. She subsequently deteriorated clinically and radiologically. Despite a number of clinical features which were atypical of leptomeningeal metastasis, adenosquamous carcinoma was found on biopsy. Her relatively indolent clinical course might be due to the initial corticosteroid treatment. This report illustrates the importance of early tissue diagnosis in uncertain cases of chronic lymphocytic meningitis.
Turcot's syndrome is characterized clinically by the occurrence of primary brain tumor and colorectal tumor and has in previous reports been shown to be associated with germline mutations in the genes APC, hMLH1, and hPMS2. Here we describe three patients with Turcot's syndrome, each having colorectal adenocarcinoma and malignant glioma. All the colorectal and brain tumors from these patients showed replication errors in most of the microsatellite loci investigated. Search for underlying germline mutations in the nucleotide mismatch repair genes revealed three different hMSH2 mutations. All colorectal tumors showed a frameshift in the A(10) tract in the coding sequence of the transforming growth factor beta type II receptor (TGFBRII) gene, but no such change was detected in any of the brain tumors. Frameshift mutation in the BAX gene was found in one colon carcinoma and mutations in insulin-like growth factor type II receptor (IGFIIR) gene in one glioma. Our data have broadened the possible mutation spectrum of patients with Turcot's syndrome. The difference in the mutation spectrum of TGFBRII, BAX, and IGFIIR between brain and colorectal tumors in these individuals suggests that the mutator phenotype may target different pathogenic pathways in the oncogenic process of the two organs.
We report a case of spontaneous epidural haemorrhage associated with metastatic radiation-induced malignant fibrous histiocytoma of the dural meninges in a patient who had been previously treated for nasopharyngeal carcinoma with radiotherapy.
Microsatellite instability (MSI) has been identified in various human cancers, particularly those associated with the hereditary nonpolyposis colorectal cancer syndrome. Although gliomas have been reported in a few hereditary nonpolyposis colorectal cancer syndrome kindred, data on the incidence of MSI in gliomas are conflicting, and the nature of the mismatch repair (MMR) defect is not known. We established the incidence of MSI and the underlying MMR gene mutation in 22 patients ages 45 years or less with sporadic high-grade gliomas (17 glioblastomas, 3 anaplastic astrocytomas, and 2 mixed gliomas, grade III). Using five microsatellite loci, four patients (18%) had high level MSI, with at least 40% unstable loci. Germline MMR gene mutation was detected in all four patients, with inactivation of the second allele of the corresponding MMR gene or loss of protein expression in the tumor tissue. Frameshift mutation in the mononucleotide tract of insulin-like growth factor type II receptor was found in one high-level MSI glioma, but none was found in the transforming growth factor beta type II receptor and the Bax genes. There was no family history of cancer in three of the patients, and although one patient did have a family history of colorectal carcinoma, the case did not satisfy the Amsterdam criteria for hereditary nonpolyposis colorectal cancer syndrome. Three patients developed metachronous colorectal adenocarcinomas, fitting the criteria of Turcot's syndrome. Thus, MSI and germline MMR gene mutation is present in a subset of young glioma patients, and these patients and their family members are at risk of developing other hereditary nonpolyposis colorectal cancer syndrome-related tumors, in particular colorectal carcinomas. These results have important implications in the genetic testing and management of young patients with glioma and their families.
Vascular endothelial growth factor (VEGF) is a hypoxia inducible angiogenic and vascular permeability factor. Although VEGF expression in glioblastoma is induced by hypoxia, its expression in renal cell carcinoma and hemangioblastoma is thought to be related to mutation of the von Hippel-Lindau (VHL) gene. It is not certain whether other lesions in VHL syndrome are associated with an elevated VEGF level. We report a VHL syndrome patient with multiple hemangioblastomas and bilateral epididymal clear cell papillary cystadenomas. In situ hybridization revealed high levels of VEGF mRNA in the clear cells of the epididymal tumor and the stromal cells of the hemangioblastoma. This lends support to the notion that upregulation of VEGF is caused by loss of the wild-type VHL protein. We postulate that the elevated VEGF levels may account for the cyst formation and vascularized stroma present in these VHL-associated tumors.
Vascular endothelial growth factor (VEGF) is a hypoxia-inducible angiogenic factor, which is known to be upregulated in most cases of glioblastoma multiforme (GBM). The expression of VEGF and its receptors in ependymomas, oligodendrogliomas, and particularly the expression during anaplastic progression of these three types of gliomas has not been studied extensively. Fifty-six gliomas, consisting of 10 ependymomas, 12 oligodendrogliomas, 3 anaplastic oligodendrogliomas, 6 astrocytomas grade II, 5 anaplastic astrocytomas, and 20 glioblastoma multiformes, were investigated for VEGF and receptor expression using in situ hybridization (ISH) and reverse transcription polymerase chain reaction (RT-PCR). Results showed that VEGF was moderately to strongly expressed in 8 of 10 ependymomas and in all anaplastic oligodendrogliomas and glioblastoma multiforme cases. These tumors displayed similar degrees of extensive necrosis and vascular proliferation, with VEGF expression consistently seen in tumor cells around necrotic areas. The VEGF expression, although present at a lower level, also was shown in 4 of 12 oligodendrogliomas, in 3 of 6 astrocytomas grade II, and in 2 of 5 anaplastic astrocytomas, with a regional rather than diffuse pattern of positive result. The findings from the in situ hybridization study correlated with the expression index, as determined by reverse transcription polymerase chain reaction. Expression of VEGF was correlated significantly with vascular proliferation (p < 10(-5)) and necrosis (p < 10(-5)), as well as with microvessel density (p = 0.002, rs = 0.41). The VEGF receptors, kinase domain region (KDR) and Fms-like-tyrosine kinase (Flt-1), also were upregulated in the tumor vasculature of glioblastoma multiforme, anaplastic oligodendrogliomas, and ependymomas with necrosis, whereas the astrocytomas grade II, anaplastic astrocytomas, and oligodendroglioma tumors tended to express a weak to nondetectable signal. Anaplastic progression in all three types of gliomas is heralded by the occurrence of small zones of VEGF-expressing cells and early vascular proliferation, followed by an accelerated phase of angiogenesis closely associated with VEGF induction around areas of necrosis and with the expression of VEGF receptors in the tumor vasculature.
A 34-year-old Chinese woman underwent successful gross total excision of a benign fibroblastic meningioma, pre-operatively diagnosed by computed tomography (CT), arising from the left lateral ventricle of the brain. After a quiescent period of 5 years, CT and magnetic resonance imaging (MRI) demonstrated tumour recurrence at the same site. Despite two further excisions of progressively malignant intraventricular meningiomas and treatment with radiotherapy, the patient rapidly developed bilateral cerebellopontine angle and spinal drop metastases. CT and MRI were useful in demonstrating the location and extent of recurrent intraventricular meningiomas, as well as metastatic spread via the cerebrospinal fluid.
To determine the efficacy of ranitidine in preventing clinically acute overt gastroduodenal (GD) complications (bleeding and/or perforation) after neurosurgery, 101 patients with nontraumatic cerebral disease considered at high risk of developing postoperative GD complications were randomized in a standard double-blind manner to receive either ranitidine (50 mg every 6 hours) or placebo medication preoperatively. Postoperative serial GD endoscopy was used to document the occurrence of complications: an overt symptomatic complication was defined as bleeding requiring blood transfusion and/or surgery. Fifty-two patients received ranitidine and 49 received a placebo preoperatively; 30 developed overt GD bleeding; nine of these received ranitidine and 21 received a placebo. Ranitidine significantly reduced the incidence of bleeding (p < 0.05). Multivariate logistic regression analysis revealed three factors of independent significance in predicting overt GD bleeding: use of a placebo drug, a gastric pH of less than 4, and a high daily volume of gastric output. The authors conclude that ranitidine is useful in preventing postoperative GD complications in high-risk neurosurgical patients.