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David Russell

Publications and source records attributed to David Russell.

45 records · Page 3Linked to original sources
PubMed2002

Cerebral microemboli and cognitive impairment.

Transcranial Doppler Ultrasound (TCD) may be used to detect cerebral microemboli in patient groups with an increased stroke risk and during invasive cardiovascular examinations and operations. Although these microemboli do not cause immediate symptoms, there is growing evidence which suggests that they may cause cognitive impairment if they enter the cerebral circulation in significant numbers. This has been studied in detail in patients who have had coronary artery bypass surgery. In these patients, an association has been found between the number of intraoperative cerebral microemboli detected by transcranial Doppler and postoperative neuropsychological outcome. It is also possible that cerebral microemboli may be the cause of cognitive impairment in patients with cerebrovascular disease. Cerebral microemboli are often found in patients with atherosclerosis, especially of the carotid arteries and aortic arch, and in patients with heart disease. There is also an increased risk for silent strokes and cognitive impairment in these patients. Prospective clinical studies are therefore required to determine if continuous cerebral microembolization to the brain will lead to progressive cognitive impairment.

Cognition Disorders↗
PubMed2002

Keratin mutations of epidermolysis bullosa simplex alter the kinetics of stress response to osmotic shock.

The intermediate filament cytoskeleton is thought to confer physical resilience on tissue cells, on the basis of extrapolations from the phenotype of cell fragility that results from mutations in skin keratins. There is a need for functional cell assays in which the impact of stress on intermediate filaments can be induced and analyzed. Using osmotic shock, we have induced cytoskeleton changes that suggest protective functions for actin and intermediate filament systems. Induction of the resulting stress response has been monitored in keratinocyte cells lines carrying K5 or K14 mutations, which are associated with varying severity of epidermolysis bullosa simplex. Cells with severe mutations were more sensitive to osmotic stress and took longer to recover from it. Their stress-activated response pathways were induced faster, as seen by early activation of JNK, ATF-2 and c-Jun. We demonstrate that the speed of a cell's response to hypotonic stress, by activation of the SAPK/JNK pathway, is correlated with the clinical severity of the mutation carried. The response to hypo-osmotic shock constitutes a discriminating stress assay to distinguish between the effects of different keratin mutations and is a potentially valuable tool in developing therapeutic strategies for keratin-based skin fragility disorders.

Actin Cytoskeleton↗
PubMed2002

Conn's dementia.

Explore the source record for details and available documents.

Dementia↗
PubMed2002

Comparison of monitor unit calculations performed with a 3D computerized planning system and independent "hand" calculations: results of three years clinical experience.

A comparison of the monitor unit calculations of a commercial 3D computerized treatment planning system (TPS) with "hand" calculations from lookup tables was made for a large number of clinical cases (greater than 13 500 treatment fields). Differences were analyzed by treatment site for prostate, rectum, cranium, and breast. The 3D TPS monitor unit calculation was systematically higher than the "hand" calculation by an amount that depended on the complexity of the treatment geometry. For simple geometries the mean difference was 1% and was as high as 3% for more complicated geometries. The higher value was attributed to an accumulation of differences introduced by multiple factors in the monitor unit calculation. Careful attention to factors such as patient contour could reduce the mean difference. "Hand" calculations were shown to be an accurate and useful tool for verification of TPS monitor unit calculations.

Algorithms↗
PubMed2002

Thrombolytic therapy in acute ischaemic stroke.

BACKGROUND: The aim of this study was to assess the feasibility, clinical effect and safety of intravenous thrombolysis with tissue plasminogen activator in patients with acute ischaemic stroke treated in an acute stroke unit. METHODS: All patients admitted within 3 h after an acute ischaemic stroke were considered for thrombolysis. Twenty-four patients were treated. RESULTS: Ten patients demonstrated early clinical improvement compatible with a positive effect of thrombolysis. Five patients demonstrated a substantial but slow clinical improvement with an uncertain relationship to thrombolysis. Nine patients did not improve. One patient developed an intracerebral haematoma and 2 developed a haemorrhagic infarction without clinical deterioration. Five patients (21%) died within the first 3 months. At follow-up after 6 months, 10 patients (42%) had achieved independence [modified Rankin Scale (mRS) 0-2], 9 (33%) had an unfavourable outcome (mRS 3-5) and 5 patients (21%) had died. None of these 5 patients died due to a treatment complication. CONCLUSIONS: This study in a small patient population suggests that thrombolysis may be administered relatively safely in an acute stroke unit without intensive care facilities. The clinical effect and safety were similar to those which have been found in large randomised studies and clinical series.

Aged↗
PubMed2002

Online automatic discrimination between solid and gaseous cerebral microemboli with the first multifrequency transcranial Doppler.

BACKGROUND AND PURPOSE: The aim of this study was to assess the first multifrequency transcranial Doppler system that was specially developed to automatically detect and discriminate between solid and gaseous cerebral microemboli. METHODS: The multifrequency transcranial Doppler instrumentation insonates simultaneously with 2.5 and 2.0 MHz. Differentiation between solid and gaseous microemboli is based on the principle that solid microemboli reflect more ultrasound at the higher than at the lower frequency, whereas the opposite is the case for gaseous microemboli. In the in vitro studies, 159 plastic spheres (50 or 80 micro m in diameter) and 105 gas bubbles (8 to 25 micro m) were studied in a pulsatile closed-loop system containing irodinium or pig blood. In vivo studies were carried out for 1 hour in 15 patients with mechanical heart valves and in 45 patients with carotid stenosis. This gave a total of 60 hours of online automatic monitoring in patients. RESULTS: In the in vitro studies, 152 of the 159 (95.6%) plastic spheres were classified as solid, and 7 (4.4%) were classified as uncertain solid. Of the 105 gas bubbles, 99 (94.3%) were classified as gaseous and 6 (5.7%) as uncertain gaseous. Thus, correct classification was made for 251 (95.1%) of the 264 embolic events studied. A comparison between the automatic multifrequency discrimination and the known embolic classification gave a kappa value of 0.897 (P<0.0001). The multifrequency Doppler classified 433 (84.2%) of the 514 emboli detected in the mechanical heart valve patients as gaseous, 74 (14.4%) as solid, and 7 (1.4%) as uncertain (3 uncertain solid, 4 uncertain gas). Thirty-two emboli were detected in 17 (38%) of the 45 carotid stenosis patients; 30 (93.7%) were classified as solid and 2 (6.3%) as uncertain solid. CONCLUSIONS: This study has shown that multifrequency transcranial Doppler can be used to automatically differentiate between solid and gaseous microemboli online. Most detected microemboli in this initial study of mechanical heart valves were classified as gaseous, whereas most were classified as solid in the patients with carotid stenosis.

Animals↗
PubMed2002

Automatic online embolus detection and artifact rejection with the first multifrequency transcranial Doppler.

BACKGROUND AND PURPOSE: The goal of this study was to assess the first multifrequency transcranial Doppler system specially developed for online automatic detection of cerebral microemboli. METHODS: The multifrequency Doppler instrumentation insonates simultaneously with 2.0- and 2.5-MHz frequencies. The detection threshold for embolus detection used in this study was a relative Doppler energy increase of >20 dB. ms, at which point the Doppler power increase was at least 5 dB and lasted >4 ms above the background energy. Four parameters were used in an optimized binary decision tree to recognize emboli: quarter Doppler shift, maximum duration limit, reference gate, and bidirectional enhancement. In in vitro studies, 200 plastic microspheres (80 micro m), 200 gas bubbles (8 to 25 micro m), and 600 artifacts were studied in a pulsatile closed-loop system. In vivo studies were carried out for 1 hour in 15 patients with mechanical heart valves and in 45 patients with carotid stenosis. This gave a total of 60 hours of online automatic monitoring in patients. RESULTS: All 400 plastic spheres and microbubbles were automatically detected and correctly classified. Of the 600 artifacts, 596 (99.3%) were correctly classified as artifacts, and 4 (0.7%) were incorrectly identified as emboli (kappa=0.992, P<0.001). The experienced observer detected a total of 554 emboli and 800 artifacts in the heart valve (521 emboli, 400 artifacts) and carotid stenosis (33 emboli, 400 artifacts) patients. With multifrequency Doppler, 546 of these emboli (98.6%) and 791 of these artifacts (98.9%) were automatically detected and correctly classified as embolus or artifact (kappa=0.953, P<0.0001). CONCLUSIONS: We found that multifrequency transcranial Doppler had a relatively high sensitivity and specificity when used to automatically detect cerebral microemboli and reject artifacts online.

Artifacts↗
PubMedDate not supplied

Instrumental investigations in primary headache. An updated review and new perspectives.

While some instrumental techniques are clearly useful for differentiating symptomatic forms from primary headache, the usefulness of certain other techniques, neurophysiological investigations in particular, in clinical practice is still debated. A Task Force of the European Federation of Neurological Societies has recently proposed guidelines and recommendations on the use of neurophysiological tests and neuroimaging procedures in non-acute headache. This article reviews many of the most important literature references relevant to this topic and looks at the prospects for future research.

Blinking↗