Cerebral hemodynamics in acute stroke: pathophysiology and clinical implications.

BACKGROUND

The capacity of the brain to regulate its blood flow in order to meet metabolic demands and to compensate for acute and chronic changes in cerebral perfusion pressure (cerebral autoregulation) is an essential protecting mechanism against cerebral ischemia.

METHODS

We reviewed existing data on methods of assessing cerebral blood flow and autoregulation.

RESULTS

Cerebral autoregulation is mechanistically complex and depends on myogenic, neuronal, endothelial, and metabolic factors. There are numerous methods of estimating cerebrovascular reserve (CVR) non-invasively including Positive Emission Tomography (gold standard), Transcranial Doppler ultrasound, dynamic contrast-enhanced perfusion Magnetic Resonance Imaging, Single-Photon Emission Computed Tomography and Xenon Computed Tomography. Since each of these techniques has its advantages and disadvantages, selection of a specific method for CVR testing depends on availability, acquired experience in interpreting the study, required precision, and cost. Cerebral autoregulation may be impaired in patients with symptomatic or asymptomatic carotid stenosis or occlusion and is associated with a higher risk of stroke or transient ischemic attack (TIA) ipsilateral to the carotid artery disease.

CONCLUSION

Assessment of CVR can help stratify patients based on their risk of stroke or TIA and select patients who may benefit from revascularization therapies. Cerebral vasoreactivity testing may be useful to evaluate cerebral autoregulation after revascularization procedures as a surrogate endpoint of vascular events related to hypoperfusion or hyperperfusion.