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Age and sex differences in cerebral hemodynamics: a transcranial Doppler study.
No full textBACKGROUND AND PURPOSE: Hemodynamic factors seem to play an important role in the
pathogenesis of cerebral ischemic events. The aim of this study was to evaluate
whether changes in cerebrovascular reactivity occur in women after menopause.
METHODS: Using transcranial Doppler ultrasonography, we studied the changes of
flow velocity after hypercapnia in the middle cerebral arteries of 45 healthy
premenopausal women (mean age, 32.3 years; range, 20 to 47 years) and 40
postmenopausal women (mean age, 54.4 years; range, 48 to 64 years). The same
measurements were recorded in two groups of healthy male subjects age matched
with premenopausal (45 subjects) and postmenopausal women (40 subjects).
Moreover, a subgroup of postmenopausal women aged 48 to 53 years (15 subjects)
were compared with a group of 15 premenopausal women of the same age. We obtained
hypercapnia with breath holding and evaluated cerebrovascular reactivity with the
breath-holding index (BHI).
RESULTS: BHI was significantly lower in postmenopausal women (0.89+/-0.3) than in
premenopausal women (1.59+/-0.3; P<0.0001) and in young (1.34+/-0.5; P<0.001) and
old men (1.20+/-0.4; P<0.04). In the latter group, BHI was significantly lower
than in premenopausal women (P<.0001). BHI values were also significantly lower
in postmenopausal than in premenopausal women of the same age (0.81+/-0.1 versus
1.34+/-0.1; P<0.0001).
CONCLUSIONS: These findings suggest that the large reduction of cerebrovascular
reactivity in postmenopausal women cannot be considered a simple factor related
to aging but is probably influenced by hormonal changes. The alteration in
cerebrovascular regulation could be involved in the increase of cerebrovascular
disease in postmenopausal women
Changes in cerebral blood flow induced by passive and active elbow and hand movements
No full textTranscranial Doppler ultrasonography (TCD) has been widely used to obtain information about changes in cerebral perfusion during motor activity after stroke. This type of application is greatly limited when severe motor deficits are present that impede the performance of an active motor task. In this study, we explored the effect of performing passive arm movements on cerebral perfusion. Twenty healthy subjects were investigated. A bilateral TCD monitoring of the middle cerebral artery (MCA) flow velocity was performed during the following experimental conditions: 1-min of active and passive flexion-extension elbow movement and 1-min of active and passive dorsal extension hand movement. Each task was performed with both left and right arms. The percentage increase in flow velocity from rest to task performance was calculated. Each task produced a significantly greater increase in mean flow velocity in the contralateral MCA with respect to the ipsilateral. When comparing the effect of passive and active tasks, no significant difference in mean flow velocity changes recorded in the ipsilateral and the contralateral MCA was detected regarding either elbow or hand movements. These findings demonstrate the possibility of obtaining information about changes in hemispheric cerebral perfusion during passive movements involving elbow and hand. This type of application deserves further attention in the study of cerebral functional changes following cerebral lesions
Correlations of flow velocity changes during passive movements and recovery from motor deficit in ischemic stroke
No full textCerebral hemodynamics in young hypertensive subjects and effects of atenolol treatment.
No full textThe aim of this study was to evaluate changes in cerebral hemodynamics in young
patients with uncomplicated hypertension before and after effective
antihypertensive treatment with a beta-blocker drug. Changes in mean flow
velocity in the middle cerebral artery from normal condition to hypercapnia were
evaluated by means of a transcranial Doppler in 42 hypertensive patients and 21
healthy subjects comparable for age and sex distribution. We obtained hypercapnia
with breath-holding and evaluated cerebrovascular reactivity with the
breath-holding index (BHI). After a baseline evaluation (time 0), patients were
randomly assigned to a placebo (group 1) or atenolol (group 2) therapy. The
evaluation was repeated after 30 (time 1) and 60 (time 2) days of treatment.
Before treatment, hypertensive patients had significantly lower BHI values (0.96
+/- 0.1 group 1 and 0.85 +/- 0.3 group 2) than controls (1.69 +/- 0.4) (P <
0.0001). During treatment, mean blood pressure significantly decreased in group 2
patients. In the same group, BHI values significantly increased with respect to
the pre-treatment evaluation: 1.39 +/- 0.2 at time 1 and 1.44 +/- 0.2 at time 2
(P < 0.0001). On the contrary, mean blood pressure and BHI values remained
unchanged in the placebo group. Furthermore, BHI values were significantly higher
in group 2 than in group 1 patients at times 1 (P < 0.001) and 2 (P < 0.0001).
These findings suggest that hypertension causes reduced capability of cerebral
vessels to adapt to functional changes. This condition, which is reversible after
treatment, could be implicated in the increased susceptibility to ischemic stroke
in hypertension
Functional recovery after stroke and cerebral blood flow changes during mental activity [Recupero funzionale dopo stroke e modificazioni del flusso ematico cerebrale durante attivita mentale]
No full textCerebrovascular reactivity in patients with carotid stenosis[Studio della reattivita cerebrovascolare in pazienti con stenosi carotidea]
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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