ISSN:1015-9770    

DOI:10.1159/000108419

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000315520

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000108421

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000108422

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000108423

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000108424

出版商:S. Karger AG    

年代:1997

数据来源: Karger

ISSN:1015-9770    

DOI:10.1159/000108425

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

We wished to characterize changes in function of the executive motor system individually and to correlate these with the degree of recovery from motor disability following stroke. Six male stroke patients underwent perfusion positron emission tomography scanning while undertaking a repetitive, graded force exertion task with the hand affected by stroke, and at rest. We correlated regional cerebral blood flow (rCBF) and force exerted, and compared the distribution of blood flow in all active states with that at rest. The statistical parametric maps of task-related flow changes that were generated were coregistered with anatomical magnetic resonance imaging scans. A comparison of force exertion with rest (categorical comparison) in the group as a whole showed fewer activations than found in normal subjects in both the infarcted and unaffected hemispheres, indicating disruption of the entire motor network. We found a polynomial correlation between synaptic activity (as indexed by blood flow change) and force exerted in 3 patients in the contralateral primary sensorimotor cortex, distinctly different from the logarithmic curve in normal volunteers. For the group there was an initial steep rise of relative rCBF at lower exerted forces, a plateau, and then a second steep rCBF increase at a force of approximately 50% of maximal voluntary contraction (MVC). The ipsilateral ventral posterior supplementary motor area (pSMA) and parietal areas showed correlated activity with force exerted that was not found in normal subjects. Coregistered functional and anatomical images in individuals indicated considerable intersubject variability in the patterns of activation of the contralateral primary motor cortex, pSMA, anterior cingulate cortex, dorsolateral prefrontal cortex, anterior opercular cortex, and parietal cortex. Compensatory actuation of cortical areas that comprise components of the sensorimotor system not normally activated by the task used favours the concept that recruitment of preexisting corticocortical and possibly parallel corticospinal pathways plays a prominent role in functional reorganization. Ipsilateral force-correlated rCBF changes were sometimes present in dorsolateral premotor, insular and parietal cortex consistent with bilateral representation of movements in these motor-associated areas. Quantitative analysis of the rCBF-force relationship provides clearer evidence for large-scale functional reorganization than simple task-control comparisons. The binominal relationship between rCBF and force suggests increased synaptic activity at approximately 50% MVC, a level at which many stroke patients experience an increased sense of effort.

ISSN:1015-9770    

DOI:10.1159/000108190

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

The effects of carotid endarterectomy (CEA) on cerebral hemodynamics in certain groups of patients with severe carotid stenosis still remain unclear. Cerebral vasomotor reactivity (CVR) is an important indicator of intracranial blood supply and cerebral autoregulation. Symptomatic and asymptomatic patients with severe carotid stenosis and impaired CVR were evaluated before and after CEA. Transcranial Doppler ultrasonography (TCD) and the Diamox test (i.v. administration of 1.0 g acetazolamide) before and 3 months after CEA were performed in 42 patients (21 symptomatic, 21 asymptomatic) with severe (70–99%) carotid stenosis. CVR was assessed as the difference between peak blood flow velocities in the middle cerebral artery ipsilateral to the carotid stenosis before and after acetazolamide injection and as percent increase of blood flow velocity after acetazolamide (ANOVA). Three months after CEA there was statistically significant improvement of CVR in asymptomatic compared with symptomatic patients (p < 0.05, ANOVA). CEA improves CVR mostly in asymptomatic patients. TCD combined with the Diamox test appears to be a useful tool in assessing cerebral hemodynamics prior to carotid surgery, and might be an additional criterion for selecting asymptomatic patients for CEA.

ISSN:1015-9770    

DOI:10.1159/000108191

出版商:S. Karger AG    

年代:1997

数据来源: Karger

摘要:

Hypertension is associated with a poor outcome in acute stroke. Paradoxically, lowering blood pressure (BP) may also worsen outcome, probably by reducing regional cerebral blood flow and worsening ischaemia. However, no large randomised controlled trials (RCTs) have directly studied the effect of BP reduction or elevation on outcome following stroke. Instead, advice on the management of BP in acute stroke is derived from small trials, case reports and anecdotal experience, and indirectly from RCTs where BP reduction was associated with a poor outcome. A systematic review of existing RCTs in acute stroke where drugs were administered which have the potential for altering BP will answer questions about the relationship between BP changes and outcome. A suitable large RCT of BP lowering or elevation could then be designed based on the findings of the review. Drugs that have been assessed in acute stroke and may lower BP include angiotensin-converting-enzyme inhibitors, beta-blockers, calcium antagonists, magnesium, naftidrofuryl, pentoxifylline, piracetam, prostacyclin and vinpocetine; those that may elevate BP include dobutamine, dopamine and hypervolaemic haemodilution. We have initiated a systematic review, under the auspices of the international Cochrane Collaboration and its Stroke Review Group, which aims to assess the relationship between drug-induced BP changes and outcome. We invite trialists or relevant studies (and systematic reviewers of such drugs) to join this collaborative project by contacting us.

ISSN:1015-9770    

DOI:10.1159/000108192

出版商:S. Karger AG    

年代:1997

数据来源: Karger