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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 138 (1996), S. 1172-1178 
    ISSN: 0942-0940
    Keywords: Meningioma ; metastasis ; malignant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Meningioma is a neoplastic growth originating from the leptomeninges. Although meningiomas are usually benign, malignant meningiomas with distant metastases occur infrequently. There is little precise information in the literature regarding the frequency of metastases in meningiomas; their incidence has been vaguely reported to be less than 1 per 1,000. Furthermore, most of the previous studies have also included haemangiopericytomas which most recent authorities do not consider meningiomas. In our experience with the management of 396 meningiomas over the past 18 years, 7 meningiomas were classified as malignant by defined histological criteria. After initially presenting as solitary intracranial neoplasms, three of the malignant meningiomas metastasized to extracranial tissues. Collectively, the metastases involved the vertebral bodies, liver, pelvis, long bones, and the spinal cord. This confers an incidence of metastasis of 0.76% when considering all the meningiomas, and an incidence of approximately 43% when considering only malignant meningioma; both percentages are significantly higher than reported previously. This high incidence of metastasis in the malignant meningioma indicates a worse prognosis than formerly assessed and also characterizes the malignant meningioma as a primary central nervous system neoplasm with one of the highest rates of metastasis. In addition, when malignant meningioma is classified by following strict criteria, the risk of metastasis in the ensuing clinical course can be predicted with a higher reliability.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 106 (1990), S. 132-135 
    ISSN: 0942-0940
    Keywords: Ethnic ; epidemiology ; cerebral aneurysm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The reported higher incidences of intracranial arterial aneurysms (IAA) in Africa and Asia raised the question of possible racial differences in aneurysm incidence. This prompted a retrospective study of the 244 cases of IAA seen at the Henry Ford Hospital (HFH) from 1979 to 1985. There were 171 whites and 73 blacks in the study group. The results showed a higher white to black case ratio (2.3∶1) than the white to black hospital population ratio (1.14∶1). If only bleeding aneurysms were considered, there were 81 whites and 52 blacks, with a white to black case ratio of 1.6∶1, thus giving only a borderline racial difference. The peak age of aneurysm incidence was the fifth decade for blacks and the sixth decade for whites. The most common aneurysm sites were: White Black Middle cerebral artery 26% 12% Posterior communicating artery 20% 27% Anterior communicating artery 16% 22%
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 126 (1994), S. 53-58 
    ISSN: 0942-0940
    Keywords: Meningioma ; recurrence ; regrowth ; radiotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recurrence of intracranial meningiomas after surgery has long been recognized, but there is still no consensus about factors responsible for recurrence. To better understand such factors, we analysed data on 276 patients with meningiomas who were treated at our institution from 1976 to 1990 (mean follow-up=5.1 years). Effects of sex, tumour histology, tumour site, and radiotherapy on recurrence were closely studied. Using World Health Organization criteria to define malignancy, 254 of the tumours were benign and 22 were atypical or malignant. For data analysis, distinction was made between “recurrence” (i.e., reappearance of tumour after total resection) and “regrowth” (i.e., tumour enlargement after subtotal removal). Recurrence was seen in 2 of 183 benign meningiomas and in 10 of 16 malignant meningiomas. Recurrence and regrowth rates for malignant meningiomas far exceeded those for benign meningiomas (p=0.001). Neither sex nor tumour site was associated with subsequent recurrences in patients whose tumours had been completely resected. The influence of radiotherapy was studied in terms of its effects on benign versus malignant meningiomas, whether given after complete or incomplete resection, and whether given after primary resection or on reoperation. We found that radiotherapy did not decrease “recurrence” or “regrowth” regardless of when administered, either at first resection or on recurrence. This was true for benign as well as malignant meningiomas. However, due to the small number in our series, we cannot conclude that radiotherapy has no beneficial role in the treatment of meningiomas. We do believe that the rate of recurrence for benign meningiomas is far lower than has been reported and that the majority of “recurrences” are in fact “regrowths” representing continuous tumour growth after incomplete removal. In fact, whenever recurrence is seen after complete surgical removal, chances are that tumour was atypical or malignant.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 128 (1994), S. 115-121 
    ISSN: 0942-0940
    Keywords: Cranial neoplasms ; dermoid cyst ; epidermoid cyst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We reviewed 22 epidermoid and 10 dermoid tumours of the skull and brain from patients operated on consecutively at Henry Ford Hospital between 1975 and 1991. There were 19 intradural (16 epidermoid, 3 dermoid) and 13 extradural (6 epidermoid, 7 dermoid) lesions. The average age at presentation was 35 years for patients with epidermoids and 15 years for those with dermoids. Common clinical presentations for patients with intradural lesions included headache, visual deficits, and seizures, whereas patients with extradural lesions harbored asymptomatic scalp masses. All patients with intradural lesions were investigated with computed tomography (CT) and cerebral angiography, and 8 patients underwent magnetic resonance imaging (MRI). Total resection was possible in 12 (92%) of 13 extradural tumours, all with excellent outcomes. Eight (42%) of the intradural tumours were completely resected. Overall, with the intradural tumours we had good to excellent results in 17 patients (90%), poor results in 1 (5%), and 1 death (5%). Re-operation was needed in 5 intradural recurrences (26%) with deterioration in only one patient's neurologic status postoperatively. From a review of ours and others' data, we conclude that 1) these tumours have an insidious onset despite significant size and mass effect as demonstrated by imaging studies; 2) CT, angiography, and particularly MRI help to define the extent of subarachnoid tumour spread and involvement of neurovascular structures, thus permitting better surgical planning; 3) a significant number of intradural tumours are difficult to excise because of their adherence to neurovascular structures, and thus are related to higher morbidity and mortality; and 4) because of extremely slow growth, complete tumour resection should not be the goal at the risk of injury to neurovascular structures.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Acta neurochirurgica 91 (1988), S. 87-94 
    ISSN: 0942-0940
    Keywords: Carotid endarterectomy ; perioperative complications ; surgical pitfalls ; prevention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary It is estimated that between 1971 and 1987 the number of carotid endarterectomies has increased from 15,000 to over 85,000 per year. Unless the procedure can be performed safely with a combined morbidity and mortality which is below the yearly risk of stroke (5%) for patients with symptomatic carotid artery disease, one should reconsider this operation as a therapeutic option. We review our experience with 891 carotid endarterectomies performed between January 1979 and June 1987. There were 579 (65%) men and 312 (35%) women of ages from 34 to 82 (median 65); risk factors included diabetes mellitus 213 (14%), hypertension 603 (68%), and smoking 630 (70%). Clinical presentation consisted of transient ischemic attacks 506 (57%), cerebral infarction with minimal neurological residual 252 (28%), stroke in evolution 3 (0.3%) and, asymptomatic stenosis 130 (15%). All patients were operated on under endotracheal anesthesia with transoperative monitoring of intra-arterial pressure, central venous pressure and arterial blood gases. Thiopental (3–5 mg/kg) and lidocaine (1 mg/kg) were given for induction and at 15 minute intervals during carotid cross-clamping. Intraluminal shunts were used in 13 (2%). A conventional (open) endarterectomy was performed in 561 (63%) and a limited endarterectomy (closed) in 330 (37%). Complications included 11 (1%) deaths, 26 (3%) developed a major neurological deficit that persisted, 30 (3%) had perioperative TIA's which resolved completely. Of the patients with preoperative neurological deficits, 33 (4%) recovered. Therefore, at one month after surgery, 854 (96%) were either as well or better than preoperatively. Of 514 (58%) postoperative angiograms, 23 (5%) showed an internal carotid artery occlusion; six of them developed an immediate postoperative cerebral infarction and one of them died, Non-neurologic complications were: cardiac 43 (5%), peripheral nerve 33 (3%), and local wound problems 20 (2%). We believe a carotid endarterectomy can be performed safely when it is done with meticulous attention to detail and consistent surgical technique founded on frequent exposure to the procedure.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 12 (1978), S. 141-158 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The convergence properties of the conjugate gradient method are discussed in relation to relaxation methods and Chebyshev accelerated Jacobi iteration when applied to the solution of large sets of linear equations which have a sparse, symmetric and positive definite coefficient matrix. The conclusion is reached that its convergence rate is unlikely to be much worse than these methods, and may be considerably better. The conjugate gradient method may either be applied to the basic unscaled or scaled equations or alternatively to various transformed equations. Preconditioning, block elimination and partial elimination methods of transforming equations are considered, and some comparative tests given for six problems.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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