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Circle of Willis collateral flow investigated by magnetic resonance angiography
M J Hartkamp1, J van Der Grond, K J van Everdingen
1Department of Radiology, University Medical Center Utrecht, the Netherlands.
Insights
The anatomy of the circle of Willis (CW) adapts to internal carotid artery (ICA) obstruction, with complete configurations and larger vessel diameters seen in patients with severe disease, indicating functional collateral flow.
Area of Science:
- Neuroscience
- Vascular Biology
- Medical Imaging
Background:
- The circle of Willis (CW) is a critical collateral pathway for cerebral blood flow.
- Internal carotid artery (ICA) obstruction necessitates effective collateral circulation.
- Understanding CW variations is vital for managing cerebrovascular disease.
Purpose of the Study:
- To investigate the anatomical variations of the CW in patients with severe symptomatic carotid obstructive disease.
- To analyze CW component diameter changes in relation to ICA obstruction severity.
- To assess the impact of collateral flow on CW morphology.
Main Methods:
- Magnetic resonance angiography (MRA) with flow direction sensitivity was performed on 75 patients with ICA stenosis or occlusion.
- Patients were categorized into four groups based on ICA obstruction severity.
- CW morphology and component sizes were compared to 100 control subjects.
Main Results:
- Patients with ICA obstruction showed significantly higher percentages of complete CW configurations compared to controls.
- ICA occlusion led to increased diameters of communicating channels, particularly posterior communicating arteries in bilateral occlusion.
- Severe ICA stenosis alone did not significantly increase CW vessel diameters.
Conclusions:
- The anatomical and functional configuration of the CW is significantly influenced by the degree of ICA obstruction.
- CW adaptations demonstrate its role in maintaining cerebral perfusion under conditions of carotid stenosis or occlusion.
Background And Purpose:
The circle of Willis (CW) is considered an important collateral pathway in maintaining adequate cerebral blood flow in patients with internal carotid artery (ICA) obstruction. We aimed to investigate the anatomic variation of the CW in patients with severe symptomatic carotid obstructive disease and to analyze diameter changes of its components in relation to varying grades of ICA obstruction and in relation to the presence or absence of (retrograde) collateral flow.
Methods:
Seventy-five patients with minor disabling neurological deficits and with ICA stenoses or occlusions were categorized into 4 groups according to the severity of ICA obstruction. This patient population reflected a relatively favorable subgroup of cerebral infarction (considering their minor neurological deficits). All subjects underwent magnetic resonance angiography, including magnetic resonance angiography sensitive to flow direction. CW morphology and the size of its components were determined and compared with those values in control subjects (n=100).
Results:
Compared with control subjects, patients demonstrated a significantly higher percentage of entirely complete CW configurations (55% versus 36%, P=0.02), complete anterior configurations (88% versus 68%, P=0.002), and complete posterior CW configurations (63% versus 47%, P=0.04). Patients with severe ICA stenosis did not show significantly increased CW vessel diameters. Patients with ICA occlusion demonstrated a high prevalence of collateral flow through the anterior CW and significantly increased diameters of the communicating channels. Patients with bilateral ICA occlusion relied on collateral flow via the posterior CW and demonstrated a bilateral increase in posterior communicating artery diameters (P<0.05).
Conclusions:
The anatomic and functional configuration of the CW reflects the degree of ICA obstruction.