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Updated: Jun 3, 2026
Functional Transcranial Doppler Ultrasound for Monitoring Cerebral Blood Flow
Published on: March 15, 2021
Cerebrovascular evoked response to repetitive visual stimulation in severe carotid disease--functional transcranial
Marina Roje-Bedeković1, Marijana Bosnar-Puretić, Arijana Lovrencić-Huzjan
1University Department of Neurology, Sestre milosrdnice University Hospital, Zagreb, Croatia. mroje@mef.hr
Insights
Patients with severe carotid artery disease show stable posterior cerebral artery (PCA) blood flow responses, indicating compensatory mechanisms are fully engaged. Healthy individuals exhibit significant changes in PCA hemodynamics, suggesting vasoreactive exhaustion.
Area of Science:
- Neuroscience
- Vascular Medicine
- Medical Imaging
Background:
- Internal carotid artery (ICA) stenosis significantly impacts cerebral blood flow.
- Posterior circulation hemodynamics and compensatory mechanisms in carotid disease are not fully understood.
- Visual evoked response (VER) can assess posterior cerebral artery (PCA) function.
Purpose of the Study:
- To evaluate hemodynamic responses in the PCA using functional transcranial Doppler (fTCD) in patients with high-grade ICA stenosis/occlusion.
- To compare PCA hemodynamic responses between patients with severe carotid disease and healthy controls.
- To assess the vasoreactivity of the posterior circulation under different visual stimulation conditions.
Main Methods:
- Functional transcranial Doppler (fTCD) was used to measure mean blood flow velocities (MBFV) and mean reaction time (MRT) in the PCA.
- 49 patients with 70%-99% ICA stenosis/occlusion and 30 healthy subjects were included.
- Measurements were taken in the dark and during white light stimulation over three 1-minute periods.
Main Results:
- In severe carotid disease patients, PCA MRT and MBFV showed no significant clinical difference during light stimulation but had statistically significant changes in the dark.
- Healthy subjects demonstrated significant differences in PCA MRT and MBFV during both dark and light conditions, indicating robust vasoreactivity.
- Healthy subjects showed a significant decrease in MBFV and prolonged vasoreactive response during light stimulation, suggesting potential vasoreactive mechanism exhaustion.
Conclusions:
- Stable vasoreactive response in the PCA of carotid disease patients suggests maximal engagement of compensatory mechanisms.
- The posterior circulation in healthy individuals exhibits significant vasoreactivity, which may be exhausted with repetitive stimulation.
- fTCD is a valuable tool for assessing posterior circulation hemodynamics and compensatory strategies in carotid artery disease.
Abstract:
Hemodynamic features of the posterior circulation were evaluated by assessing visual evoked response in posterior cerebral artery (PCA) by means of functional transcranial Doppler (fTCD) in 49 patients with high-grade (70%-99%) internal carotid artery (ICA) stenosis or occlusion and 30 healthy subjects. Mean blood flow velocities (MBFV) and mean reaction time (time to peak velocities) (MRT) in each PCA were measured in the dark (closed eyes) and during white light stimulation (opened eyes, looking at the electric bulb), during three consecutive repetitive periods of 1 minute each. In the group of severe carotid disease patients, there was no difference in MRT in PCA during the white light stimulation (P=0.1), whereas in the dark MRT values showed a statistically significantly prolonged visual evoked response (P=0.02), but with no clinical relevance. MBFV values did not differ significantly during white light stimulation (P=0.1), whereas in the dark the difference was also statistically significant (P=0.03), but with no clinical relevance. On the contrary, in the group of healthy subjects, MRT values differed significantly both during white light stimulation (P=0.0005) and in the dark (P=0.00054), showing a significantly prolonged visual evoked response. During white light stimulation, MBFV showed significant decrease and prolonged vasoreactive response (P=0.004). Prolonged vasoreactive response in PCA in healthy subjects during repetitive measurements may indicate exhaustion of the vasoreactive mechanisms. In carotid disease patients, stable vasoreactive response may indicate that the compensatory mechanisms of the posterior circulation are always maximally engaged to compensate for carotid insufficiency.