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A Keel

Publications and source records attributed to A Keel.

9 recordsLinked to original sources
PubMed2000

Prediction of angiographic carotid artery stenosis indexes by colour Doppler-assisted duplex imaging. A critical appraisal of the parameters used.

The aim of our study was to establish colour Doppler-assisted duplex imaging (CDDI)-criteria to predict an angiographic internal carotid artery (ICA) stenosis of at least 70%, according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trialists (ECST) methods of measurement. In the following, we describe the findings in 79 patients who were screened for carotid endarterectomy by CDDI and further evaluated by digital subtraction angiography (DSA). In 158 carotid arteries, 107 stenoses of > 30% and nine occlusions were found. Receiver operator characteristic graphs were constructed in order to calculate sensitivities and specificities of the assessment by CDDI in the prediction of high-grade stenoses determined by angiography. Optimal cut-off points were defined by highest accuracy which reflects the combination of high sensitivity and specificity. The critical index of a high-grade ICA stenosis according to the ECST method could be predicted with an accuracy greater than 90% by a systolic peak velocitiy of 1.25 m/s or an area reduction by CDDI of 70%. Corresponding values, 1.6 m/s and 80% area reduction, predicted the stenosis indexes according to the NASCET method less reliably, with accuracies of between 80% and 90%. Flow velocity criterion was slightly less accurate than the area reduction criterion by CDDI. Finally, double-blind evaluation performed by two readers per examination modality showed that the measurement of area reduction in CDDI is at least as reliable as stenosis indexes according to ECST and NASCET methods.

Adult↗
PubMed2000

Disturbed functional brain interactions underlying deficient tactile object discrimination in Parkinson's disease.

Somatosensory discrimination of cuboid objects was studied in a group of healthy volunteers and patients with Parkinson's disease using regional cerebral blood flow (rCBF) measurements obtained with positron emission tomography (PET) and 15O labeled water [H2 15O]. A 6-[18F]-fluoro-L-dopa (FDOPA) PET scan demonstrated that the patients may be grouped into those with normal and those with abnormally lowA FDOPA uptake in the caudate nucleus. The categorical group comparisons revealed that task-induced rCBF increases were deficient in bilateral motor and sensory cortical areas in the Parkinson patients. Moreover, deficient rCBF increases were evident in the mesial and right dorsolateral prefrontal cortex for patients in a more advanced disease state, who showed low FDOPA uptake in the caudate nucleus. A principal component analysis (PCA), performed on the rCBF data, identified three patterns (principal components, PCs) that differentiated patients from normals. The first PC represented a right-hemisphere dominant, bilateral group of brain areas known to be involved in tactile exploration. A second PC reflected a cortical-subcortical pattern of functional interactions, comprising cortical areas important for working memory processes. The third group-differentiating PC revealed a pattern of functional interactions involving bilateral temporo-parieto-occipital association cortices, which was consistent with a hypothesized supramodal network necessary for object discrimination. In an additional subgroup analysis, greater expression of the third PC pattern predicted greater caudate FDOPA uptake in patients. Our neuroimaging data revealed a disturbance of distinct patterns of brain functional interactions related to the sensorimotor deficit in Parkinson's disease and to deficits of cognitive information processing deficits in the more advanced stage of Parkinson's disease.

Adult↗
PubMed1999

Impaired somatosensory discrimination of shape in Parkinson's disease: association with caudate nucleus dopaminergic function.

Tactile discrimination of macrogeometric objects in a two-alternative forced-choice procedure represents a demanding task involving somatosensory pathways and higher cognitive processing. The objects for somatosensory discrimination, i.e., rectangular parallelepipeds differing only in oblongness, were presented in sequential pairs to normal volunteers and 12 parkinsonian patients. The performance of patients was significantly impaired compared to normal volunteers. From a biochemical point of view, the patients were characterized by a severely reduced 6-[18F]-fluoro-L-dopa (FDOPA) tracer metabolism in the basal ganglia, as measured using positron emission tomography (PET). Furthermore, reduced specific FDOPA metabolism in the putamen was consistent with the impaired motor capacities of the patients. The reduced specific FDOPA-uptake within the caudate nucleus was associated with additionally diminished somatosensory discrimination. This association, of low perception during task performance and decreased FDOPA-uptake, provides direct evidence for the role of the caudate nucleus in the cognitive part of the task. We suggest that directed attention and working memory were critically involved as a result of disturbed interactions between the head of the caudate nucleus and the dorsolateral prefrontal cortex. Furthermore, there were indications of an additional involvement of the mesolimbic system, which might be of importance during challenging situations such as forced choice. We conclude that differential effects on parts of the basal ganglia, during evolution of the degenerative process characteristic of Parkinson's disease, have profound consequences on the performance of skills, as shown here for a somatosensory discrimination task.

Adult↗
PubMed1998

Somatosensory discrimination of shape: prediction of success in normal volunteers and parkinsonian patients.

Tactile discrimination of macrogeometric objects in a two-alternative forced-choice procedure represents a complex task including somatosensory and higher-order cognitive processing. The objects for somatosensory discrimination were rectangular parallelepipeds that differed in oblongness only. They were presented in sequential pairs to 12 normal volunteers and 13 parkinsonian patients. Owing to the dichotomy of the task, we calculated estimates of the probability of a correct answer by a binomial approach. The probability of a correct answer could be calculated on the basis of a logistic model ensuring that the probability values lie in the interval [0, 1]. The relationship between the probability of a correct answer and the difference in oblongness of the objects could be described solely by one coefficient determined by logistic regression. This coefficient summarized the effectiveness of the simultaneous and consecutive operations inherent in the task and allowed characterization of performances in groups and individuals.

Adult↗
PubMed1984

[Can factors of prognostic significance be identified during rehabilitation of cardiac infarct patients?].

In a follow-up study of myocardial infarction patients who had followed the rehabilitation program at this clinic, a cardiac mortality rate of 3.8% (35 out of 930 patients) and a reinfarction rate of 2.3% (21 out of 930 patients) were observed in the 16.6 months after infarction. The relationship between 15 variables and these cardiac events was examined by cross-tabulation and then by Fischer's test of independence. No prognostic factors for reinfarction were found. However, there were 4-risk-indicators which were predictive of early mortality: diabetes, severe complications during the hospital course, congestive heart failure and exercise-induced, complex ventricular arrhythmias. While a single risk-indicator was of little prognostic significance, a combination of two or more identified patients at high risk of subsequent mortality.

Arrhythmias, Cardiac↗
PubMed1983

Splenectomy and infection in Hodgkin's disease.

The incidence of infection in 56 patients with Hodgkin's disease who had undergone staging laparotomy with splenectomy was compared with that of 28 non-splenectomized patients with Hodgkin's disease treated concurrently. The results suggest that splenectomy does not result in a major change in the incidence of infection experienced by such patients with stage II or stage III disease. Aggressive therapy may be of greater importance in increasing the susceptibility to infection in Hodgkin's disease.

Adolescent↗
PubMed1983

Improved vascular access for patients receiving chemotherapy.

Indwelling central venous catheters were used for vascular access in 25 oncology patients. The lines were used for sampling, administration of blood products, chemotherapeutic agents, parenteral nutrients and occasionally plasmapheresis. The complication rate was no higher than in reported series in which the catheters were reserved for parenteral nutrition. We believe that a central venous cannula can be safely used as the sole means of vascular access in those patients with consequent psychological and practical benefits.

Adolescent↗