Due to the dynamic changes of cerebral vessel tone a relatively constant cerebral blood flow is maintained in spite of changes of systemic blood pressure. However, the regional cerebral blood flow adapts to the dynamically changing metabolic demand. The assurance of an adequate blood supply to brain tissue is provided by the vasodilator and vasoconstrictor ability of the cerebral vessels. The measure of the cerebral vasodilator capacity can be investigated by different methods depending on the aim of the investigation. Thus, autoregulation, cerebrovascular reactivity, and neurovascular coupling can be examined. The examination of autoregulation is based on the analysis of blood pressure and cerebral blood flow velocity changes, while cerebral vasoreactivity or neurovascular coupling is evaluated by the flow velocity changes, evoked by different vasoactive (carbon-dioxide, acetazolamide, neuronal activation) stimuli. The present paper summarizes the advantages and disadvantages of the above mentioned methods.
Keywords: Transcranial Doppler, cerebral blood flow, regulation, vasoreactivity, neurovascular coupling