Reserve Capacity In Patients Research Articles

Cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease: assessment with dynamic susceptibility contrast-enhanced MR imaging and the acetazolamide stimulation test.

To quantitatively assess cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease. In 21 symptomatic patients with occlusive cerebrovascular disease, magnetic resonance (MR) imaging was performed with a 1.5-T system. Before, during, and after a brief bolus injection of gadopentetate dimeglumine into the antecubital vain, a series of 32 rapid T2*-weighted gradient-echo images of two different sections were acquired simultaneously to measure the concentration-time-curves in the brain tissue and in the brain-feeding arteries. Principles of indicator dilution analysis were applied to compute regional cerebral blood flow (rCBF) and volume. Each patient underwent two examinations, the first before and the second after acetazolamide stimulation. In the asymptomatic hemisphere, a mean increase in rCBF value of 47.1% was observed after acetazolamide stimulation. In the affected areas of the symptomatic hemisphere, a statistically significantly reduced response to acetazolamide stimulation was found, indicating a severely compromised cerebrovascular reserve capacity. MR imaging with the described techniques provides quantitative information about the cerebrovascular reserve capacity in patients with occlusive cerebrovascular disease.

Magnetic resonance imaging of regional cerebral blood oxygenation changes under acetazolamide in carotid occlusive disease.

Gradient-echo magnetic resonance imaging can demonstrate changes in cerebral blood oxygenation with high spatiotemporal resolution. We have previously shown that this technique allows monitoring of autoregulatory responses under vasodilatory stress in the healthy human brain. Here the approach has been extended to assess impairment of the autoregulatory reserve capacity in patients with carotid occlusive disease. We studied four patients with unilateral occlusion of the internal carotid artery on a 2.0-T clinical high-field magnetic resonance system. Oxygenation-sensitive imaging was based on long-echo-time, gradient-echo sequences (repetition time, 62.5 milliseconds; echo time, 30 milliseconds) with low flip angles (10 degrees) to emphasize changes in blood oxygenation rather than flow velocity. Dynamic recording monitored signal intensities before and after injecting 1 g of acetazolamide. In sections covering the hand area of the primary sensorimotor cortex, acetazolamide-induced magnetic resonance signal increases were attenuated in the vascular territories of occluded arteries. Lateralization of responses in the left and right hemispheric parts of the section corresponded to decreased hemodynamic reserve capacity as measured globally by transcranial Doppler ultrasonography. The present findings indicate that magnetic resonance imaging can demonstrate exhaustion of the autoregulatory reserve capacity when monitoring cerebral blood oxygenation changes during vasodilatory stress. We suggest that this method can help to evaluate regional cerebral hemodynamics in patients with carotid occlusive disease.

The Effect of Acetazolamide on Regional Cerebral Blood Oxygenation at Rest and under Stimulation as Assessed by MRI

The sensitivity of gradient echo magnetic resonance imaging (MRI) to changes in cerebral blood oxygenation (CBO) has been introduced for mapping functional brain activation. Here, we report that this approach allows monitoring autoregulation in the human brain under vasodilatory stress. Following the administration of acetazolamide, signal intensities of deoxyhemoglobin-sensitive images increased in cortical and subcortical gray matter and to a lesser extent in white matter. This result reflects a venous hyperoxygenation stemming from an increase in cerebral perfusion with oxygen consumption remaining constant. In addition, pharmacologic induction of vasodilation attenuated activity-related MRI signal changes in the visual cortex under photic stimulation. Although intersubject variability was high, this finding indicates individually persisting autoregulatory responsiveness to functional challenge despite an "exhausted" reserve capacity. It is suggested that recording CBO by MRI will foster our understanding of modulation of vasomotor tone and cerebral perfusion. Furthermore, this technique may prove valuable for assessing the cerebrovascular reserve capacity in patients with carotid artery occlusive disease.

Cerebral blood flow and CO2 responsiveness as an indicator of collateral reserve capacity in patients with carotid arterial disease: Bullock R, Mendelow AD, Bone I, et al. Br J Surg 1985; 72:348-51

Cerebral blood flow and CO2 responsiveness as an indicator of collateral reserve capacity in patients with carotid arterial disease: Bullock R, Mendelow AD, Bone I, et al. Br J Surg 1985; 72:348-51

Cerebral Blood Flow and CO2 Responsiveness as an Indicator of Collateral Reserve Capacity in Patients with Cartoid Arterial Disease

Cerebral Blood Flow and CO2 Responsiveness as an Indicator of Collateral Reserve Capacity in Patients with Cartoid Arterial Disease

Studies On Pituitary-Gonadal Endocrine Function In XYY Men

Serum luteinizing and follicle-stimulating hormones and testosterone levels were studied in 11 patients with 47-XYY chromosomes and a comparison was made to normal men and patients with other testicular diseases, including Klinefelter’s syndrome. Serum follicle-stimulating hormone levels in patients with XYY chromosomes were elevated significantly in comparison to those in normal men but lower than those in men with Sertoli cell only syndrome and Klinefelter’s syndromes. Serum luteinizing hormone levels were somewhat elevated and serum testosterone levels were somewhat low in comparison to normal men, although the difference was not significant. Results of the short-term human chorionic gonadotropin stimulation test suggested almost normal Leydig cell reserve capacity in patients with XYY chromosomes