Unruptured intracranial aneurysm as a cause of cerebral ischemia.
ABSTRACT Unruptured intracranial artery aneurysms (IAs) can be revealed by cerebral ischemia. Little is known on the clinical course and outcome of patients with this condition. We report our findings in a consecutive series of 15 such patients.
We retrospectively analyzed patients with ischemic stroke (IS) or transient ischemic attack (TIA), unruptured IA on the symptomatic cerebral artery, and no other potential cause of cerebral ischemia consecutively treated in a tertiary stroke unit.
Fifteen patients (ten women, and five men) were identified. Their mean age was 49.7 years (range, 37-80 years). Ten patients presented with IS, and five with TIA. The median diameter of IA was 7.5mm (range, 2.5-23 mm). Aneurysm thrombosis was found on imaging in 9/10 patient with IS, and 1/5 patients with TIA (p=0.017). Thirteen patients were given an antiplatelet agent. Mean follow-up until last visit or treatment of aneurysm was 393 days (median 182 days; range, 6-1825 days). There was no ischemic recurrence. Partial or complete recanalization of aneurysm thrombosis occurred in 7/10 patients. Two patients, both with initial aneurysmal thrombosis and on antiplatelet therapy, experienced aneurysm rupture.
Unruptured IA is a rare cause of IS/TIA. IS is associated with aneurysm thrombosis. Our findings suggest that aneurysm thrombosis is a dynamic process which is associated with a low rate of ischemic recurrence on antiplatelet therapy but may be followed by subarachnoid hemorrhage.
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ABSTRACT: Five plant communities in Western Australia, as well as selected desert and Rocky Mountain species of the western USA, were surveyed to evaluate associations among leaf structure, orientational properties, and the sunlight exposure and precipitation characteristic of each community. Selected leaf structural features have been associated previously with photosynthetic function and included shape, thickness, the ratio of thickness to width, stomatal distribution, leaf surface coloration, and the number and distribution of palisade cell layers. Decreases in annual precipitation (<4 to over 15 cm/yr) and increases in total daily sunlight (4.2 to 29.2 mol photons/m1) corresponded strongly to an increase in the percentage of species in a given community with more inclined (more inclined than +/- 45 degrees from horizontal) or thicker leaf mesophyll (>0.4 mm) leaves. Also, the percentage of species with a leaf thickness to width ratio >0.1, which were amphistomatous, or which had palisade cell layers beneath both leaf surfaces, increased from >20% in the highest rainfall and lowest sunlight community to >80% in the community with least rainfall but greatest sunlight exposure. Over 70% of the species in the most mesic, shaded community had lighter abaxial than adaxial leaf surfaces (leaf bicoloration). All of the above structural features were positively associated with a more inclined leaf orientation (r1 = 0.79), except for leaf bicoloration, which was negatively associated (r1 = 0.75). The ratio of adaxial to abaxial light was more strongly associated with leaf bicoloration (r1 = 0.83) and the presence of multiple adaxial and isobilateral palisade cell layers(r1 = 0.80) than with total incident sunlight on just the adaxial leaf surface (r1 = 0.69 and 0.73, respectively). These results provide field evidence that leaf orientation and structure may have evolved in concert to produce a photosynthetic symmetry in leaf structure in response to the amount of sunlight and other limiting factors of the community. This structural symmetry may serve fundamentally to regulate the distribution of both light and CO2 levels inside the leaf and, thus, increase photosynthetic CO2 uptake per unit leaf biomass.American Journal of Botany 01/1998; 85(1):56. · 2.59 Impact Factor
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ABSTRACT: Photosynthetic adaptation in terrestrial vascular plants involves a complex interaction of components that extend across a broad structural and spatial hierarchy, often functioning in concert with one another at multiple scales. Thus, understanding the evolutionary mechanisms leading to these adaptations requires evaluation across the entire spectrum of plant form from the chloroplast to the landscape. Adaptive traits across this structural/spatial hierarchy can emerge at any level and then feed-back or feed-forward to cause adaptive changes at adjacent levels. Today's sophisticated instruments enable direct measurement of photosynthesis at most of these hierarchical levels and across phylogenetic boundaries. As a result, identification of functional properties in plant form (architectural and spatial), independent of physiological processes, is becoming a reality. In this review we focus on one apparent theme across this hierarchy of organizational complexity—the impact of plant form on the distribution of incident sunlight to photosynthetic surfaces, and the transfer and processing of mass nutrients (e.g. CO 2 and water). The trade-offs and net effects of these exchange processes drive photosynthetic adaptation, and appear to be related to economic efficiencies rather than simply magnitude.Castanea 03/2009; · 0.36 Impact Factor
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ABSTRACT: Architecture can vary widely across species. Both steeper leaf angles and increased self-shading are thought to reduce potential carbon gain by decreasing total light interception. An alternative hypothesis is that steeper leaf angles have evolved to improve day-long carbon gain by emphasising light interception from low angles. • Here we relate variation in architectural properties (leaf angle and leaf size) to cross-species patterns of leaf display, light capture and simulated carbon gain in branching-units of 38 perennial species occurring at two sites in Australian forest. Architectural comparison was made possible by combining 3D-digitising with the architecture model YPLANT. • Species with shallow angled leaves had greater daily light interception and poten-tially greater carbon gain. Self-shading, rather than leaf angle, explained most variance between species in light capture and potential carbon gain. Species average leaf size was the most important determinant of self-shading. • Our results provide the first cross-species evidence that steeper leaf angles func-tion to reduce exposure to excess light levels during the middle of the day, more than to maximise carbon gain.New Phytologist 01/2003; 158:509-525. · 6.74 Impact Factor