Biomedical subjects
Publications and source records attributed to G Sieben.
We report two cases of a dural arteriovenous fistula of the anterior cranial fossa, one causing subarachnoid hemorrhage and one detected accidentally. The first case was incompletely treated by neurosurgery, and the second one was referred for endovascular therapy. Both fistulas were successfully occluded by transvenous embolization by using electrolytically detachable coils.
BACKGROUND: A Kohonen topological map is an artificial intelligence system of the connectionist school (neural networks). The map learns the typical features of the subclasses in the learning set by means of a shortest Euclidean distance algorithm, after which self-adaptation of the neurons occurs. By its ability of self-organization and generalization, a Kohonen map is useful for pattern recognition, and its application in the medical field as an aid for decision making seems promising. This study describes the use of a Kohonen topological mapping system in the classification of renal diseases as being glomerular or tubular on basis of clinical characteristics and laboratory results. METHODS: Forty-one parameters from 75 patients were retrospectively retrieved and used to train four different Kohonen maps of 10 x 10 neurons. For reference diagnostic classification, we referred to the results of the light-microscopic examination. The classification of the patients by the four different Kohonen networks was compared to the classification by a rule-based system and by three nephrologists. We also developed a 'hybrid' decision system that makes a classification on basis of the opinion of the four networks and that of the rule-based system. RESULTS: The results show that a Kohonen map is capable of classifying the patients as having glomerular or tubular disease with a higher sensitivity and predictive value than the nephrologists and the rule-based system, and that the best classification was performed by the hybrid system: sensitivity and predictive value for the diagnosis 'glomerular' respectively 100 and 88% for the network with the most adequate results, 90 and 83% for the nephrologists, 90 and 95% for the rule-based system, and 95 and 96% for the hybrid system; sensitivity and predictive value for the diagnosis 'tubular' respectively 50 and 100% for the neural networks, 31 and 45% for the nephrologists, 81 and 68% for the rule-based system, and 87 and 82% for the hybrid system). CONCLUSION: We conclude that a Kohonen map is capable of classifying the patients as having glomerular or tubular disease with a high sensitivity and predictive value. The rule-based system performs worse than the neural networks. The most adequate results were obtained with the hybrid system.
This study describes the use of a topological mapping system in the classification of cerebral tumours and the development of a decision support system based upon that classifier. Fourteen pathological parameters from two hundred primary cerebral tumours are presented as vectors to a topological map. The map, consisting of a grid of neurones, learns the features of each tumour by means of a shortest Euclidean distance algorithm, after which self adaptation of the neurons occurs. An LVQ algorithm performs the final classification. Study of the map reveals that it can correctly classify tumors following their malignancy potential and their cytogenesis. The decision support system uses the network at its core and helps not only in reaching a diagnosis but also in finding the optimal way to reach that diagnosis. The usefulness of such a mapping system lies in the field of education, clinical research and medically acceptable cost reduction.
This study was undertaken to analyse epidemiological and methodological differences in referral pattern, examination techniques and distribution of diagnoses among different European EMG laboratories. Seven European EMG laboratories filled in questionnaires and sampled 700 cases retrospectively. The use of needle or surface electrodes for nerve studies and the selection of quantitative techniques for muscle studies exhibited considerable variation. The pattern of referral varied with respect to the type of referral source and the neurological expertise of the referring physician. The proportion of patients without any neurophysiological abnormality ranged from 16 to 33%. The 3 most common diagnostic groups were mononeuropathies, polyneuropathies and radiculopathies although a great inter-laboratory variation was found. The proportion of patients with multiple diagnoses varied from 0 to 23% and most of these diagnoses were from a few known combinations. The presence of an inter-laboratory variation suggests that the quality of the EMG examination may be improved by focussing on the use of techniques, strategies and diagnostic criteria.
A double-blind placebo-controlled cross-over trial was carried out to evaluate the efficacy and safety of the combined serotonin-dopamine antagonist risperidone in mentally retarded patients with persistent behavioural disturbances. After an observation period of 1 week, risperidone 4-12 mg or placebo was administered during 3 weeks as add-on treatment to the existing medication, followed by a 1-week single-blind placebo wash-out, and another 3 weeks of double-blind treatment with the cross-over medication. Thirty-seven patients participated in the trials; 30 completed the study. Risperidone was significantly superior to placebo in its effect on the Aberrant Behaviour Checklist and the Clinical Global Impression. The Extrapyramidal Symptom Rating Scale did not show any differences between risperidone and placebo. Two patients experienced hypotension at the start of the risperidone administration. Sedation and drowsiness were the most frequently reported treatment-emergent adverse events. The results of this trial warrant further investigation into the therapeutic assets of risperidone in this indication, as add-on therapy and as monotherapy.
Moclobemide was compared with amitriptyline for antidepressant efficacy, safety and tolerance. Two studies were conducted, both over at least 4 weeks; in the first, 8 patients were given moclobemide in doses ranging from 300 to 328 mg, and 9 patients amitriptyline in doses of 75 to 96 mg; in the second, the numbers were 13 on moclobemide and 14 on amitriptyline, and the mean doses were 294-408 mg and 95-129 mg respectively. Both studies showed the 2 treatments to be equally effective, and there were no significant differences at any point. Moclobemide appeared slightly more effective and slightly better tolerated than amitriptyline, but the numbers were too small for any valid conclusion.
Malignant brain tumors respond poorly to chemotherapy. This therapeutic resistance is the result of the marked heterogeneity of malignant gliomas in vivo and in vitro. Different factors, as specific markers, DNA distribution curves, morphology, chromosomal constitution, invasiveness and growth characteristics are considered for the understanding of the biology of malignant brain tumors. A better knowledge of this biology should provide new chemotherapeutic strategies.
Two double-blind multicenter trials were performed to compare the antihypertensive action of ketanserin, at an oral dosage of 20 mg three times daily, with that of placebo over a period of four to six weeks. A subset of patients was treated in a crossover fashion for either four weeks (36 patients) or six weeks (24 patients). The patients had essential hypertension, with a diastolic blood pressure greater than or equal to 95 mmHg measured in sitting position at the end of a placebo run-in period of at least one week. In a first trial, 78 of 82 patients completed the four-week study period, where the mean drop of the systolic/diastolic blood pressure was -14/-12 mmHg in the ketanserin group (n = 32) versus -8/-5 mmHg in the placebo group (n = 46). This difference is statistically significant (p = 0.05/p less than 0.01). In 13 patients who after the initial ketanserin treatment were further treated with placebo in crossover for four weeks, the blood pressure rose slightly (+1/+3 mmHg). In the alternative group (n = 23), the blood pressure fell by -10/-7 mmHg after placebo and decreased further by -10/-8 mmHg after ketanserin. In a second trial, 24 patients completed a two by six week crossover treatment. In 12 patients assigned to the sequence placebo-ketanserin, there was a drop of the systolic/diastolic blood pressure by -7/-4 mmHg after placebo and an additional drop by -26/-10 mmHg after ketanserin.(ABSTRACT TRUNCATED AT 250 WORDS)
The influence of AZQ, a chemotherapeutic agent, on the DNA-distribution of human cerebral tumours in short-term culture was studied by means of a MPV II cytofluorometer. The cell cultures were exposed to increasing concentrations of AZQ during 5 days. The results showed that AZQ has no cell phase-specific activity. The influence on the DNA-distribution varied considerably in the examined tumours. It is hypothesised that the effect of AZQ might depend upon the initial DNA-distribution of human cerebral tumours, hyperdiploid tumours being more vulnerable.
The clinical history is presented of a 69-year-old man with a disease starting with a herpes zoster infection and an acute ascending myelopathy, and ending with an intracerebral hemorrhage. The postmortem examination revealed multiple angiitis lesions, restricted to the central nervous system. In review of the 31 previously described cases there were four other patients in whom the granulomatous angiitis of the nervous system (GANS) was associated with a herpes zoster infection. The relation between both disorders is discussed.
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In this prospective neuropathologic study, Wernicke's encephalopathy appears to be the most frequent intracranial complication of treated patients with tumours of the lymphoid-hemopoietic systems. The highest incidence of this encephalopathy is found in elderly and in patients with a prolonged survival. The chronic form of Wernicke's encephalopathy is most commonly observed.
During a period of 10 years, 2782 brains were examined at post-mortem and in 17 cases metastases were attached to the dura mater, 8 presenting as multiple nodules 6 as a single nodule and 3 as diffuse dural thickening. The primary growths were, in equal proportions sarcomas, epitheliomas and lymphoid tumours. In contrast to the frequent location of metastases in the axial skeleton (9 cases), brain involvement was rarely observed (2 cases). The clinical findings were non-specific. The difference in biological behaviour between subdural and intracerebral metastases is stressed.
In a series of 312 postmortem confirmed cerebral infarcts the clinical history was reviewed and the pattern of the strokes compared to the involved vascular territory. A high incidence of silent strokes was observed, and reversible neurological deficits occurred mostly in infarcts in the vertebrobasilar circulation, in particular in those in the supply area of the posterior cerebral and posterior inferior cerebellar arteries.
The clinicopathological findings of a 50-year-old man, who developed cervicothoracic syringomyelia at the age of 25 are presented. He was given radiation therapy at the age of 33. At the age of 57 he developed a foramen jugulare syndrome on the left, caused by a low grade leiomyosarcoma. Etiologically, the most attractive hypothesis appears to be that the tumour was induced by radiation therapy administered 24 years previously.
Out of series of 240 patients, with proved cerebral infarcts at necropsy, 14 with a clinical history of epilepsy were selected. The possible etiology of seizures was analyzed by comparing the clinical and pathological data. It appeared from this series that epileptic spells, preceding for years the occurrence of a stroke, were due to other causes than to cerebrovascular insufficiency. It was also difficult to separate apoplectic seizures from those occurring due to scar formation after a cerebral infarct, as postapoplectic epilepsy was induced either by the occurrence of a new stroke or by hemodynamic disturbances. Severe generalized or local hemodynamic and metabolic disturbances were also noted in cases of convulsions resulting from a cerebral infarct.
From 220 necropsies of patients with cerebral infarcts, 5 were selected, in which the clinical history revealed typical parkinsonian symptoms with a progressive course of the extrapyramidal disorder. No correlation could be found between the location and the size of the infarcts on the one hand and the signs of parkinsonism on the other hand. In the 5 cases presented, the substantia nigra showed patchy areas of neuronal degeneration without any Lewy bodies nor neurofibrillary changes, around a pronounced status cribrosus in areas irrigated by paramedian branches of the mesencephalic arteries. Similar neuropathologic findings were present, but to a minor degree, in 2 of 5 cases of pseudo-bulbar palsy. Some extrapyramidal features were also present. It is proposed that is some rare instances, status cribrosus may be responsible for nigral degeneration and for the occurrence of parkinsonism.
Cytophotometric DNA determination was performed on 11 surgically resected oligodendroglial tumours and on oligodendroglial cells in two normal brains. The results are compared with the histological findings, the mitotic index and the degree of clinical malignancy. In this type of glioma there is no correlation between the DNA pattern and the histological appearances and the mitotic index. It is concluded that an aneuploid DNA distribution curve corresponds to a bad prognosis, whilst a diploid DNA curve does not allow prediction of the degree of clinical malignancy.