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[Cerebral perfusion reserve and collateral circulation in patients with internal carotid stenosis]
W Reiche1, R Schäfer, M Müller
1Abteilung für Neuroradiologie, Universität des Saarlandes, Homburg/Saar.
Insights
Cerebral hemodynamics in carotid disease patients depend on collateral circulation, not just stenosis severity. Compromised regional cerebral perfusion reserve (rCPR) strongly correlates with specific collateral pathways like leptomeningeal or ophthalmic arteries.
Area of Science:
- Neuroscience
- Radiology
- Vascular Medicine
Background:
- Cerebral hemodynamics are significantly affected by extra- and intracranial collateral networks in patients with carotid disease.
- Understanding the relationship between collateral circulation and regional cerebral perfusion reserve (rCPR) is crucial for managing carotid artery stenosis or occlusion.
Purpose of the Study:
- To compare regional cerebral perfusion reserve (rCPR) findings with angiographically proven collateral circulation in patients with carotid disease.
- To investigate the correlation between compromised rCPR and specific types of collateral pathways.
Main Methods:
- 41 patients with carotid stenosis or occlusion underwent 99mTc-HMPAO-SPECT and dynamic Xe-CT scans before and after acetazolamide stimulation.
- Regional cerebral perfusion reserve (rCPR) was quantified using ratios of absolute rCBF (Xe-CT) and count density (HMPAO-SPECT) post-stimulation.
- Patients were categorized into groups based on collateral circulation patterns: residual carotid perfusion, Circle of Willis, and leptomeningeal/ophthalmic artery collaterals.
Main Results:
- Significant differences in rCPR values were observed between patients with Circle of Willis collaterals and those with leptomeningeal/ophthalmic artery collaterals using both Xe-CT and HMPAO-SPECT.
- Compromised rCPR (<95%) was prevalent in patients with leptomeningeal or ophthalmic artery collateral circulation (13/14 with Xe-CT, 11/14 with HMPAO-SPECT).
- Patients with Circle of Willis collateralization showed normal rCPR with both imaging methods, while those with residual carotid perfusion had mixed results.
Conclusions:
- Cerebral hemodynamics in carotid disease are critically dependent on the collateralization network, rather than solely on the degree of internal carotid artery stenosis.
- A decreased rCPR in a vascular territory ipsilateral to carotid stenosis or occlusion is a strong indicator of leptomeningeal or ophthalmic artery collateral circulation.
Abstract:
The cerebral hemodynamics in patients with carotid disease is influenced by a network of extra- and intracranial collaterals. The purpose of this study was to compare the findings of regional cerebral perfusion reserve (rCPR) with angiographically proven collateral circulation. In 41 patients (28 men, 13 women, age 63 +/- 10 years) with angiographically proven carotid stenoses or occlusions (30 stenoses, 11 occlusions) 24 99mTc-HMPAO-SPECT and 25 dynamic Xe-CT investigations were conducted, both before and after acetazolamide stimulation. rCPR was quantified as the ratio (1) of the absolute rCBF values obtained by Xe-CT and (2) of the count density measured by HMPAO-SPECT of the acetazolamide administration. A rCPR of less than 95% in a vascular territory was classified as compromised rCPR. A recent CT examination was available in all cases. According to the angiographic findings the patients could be classified into (1) group A (n = 9) with residual carotid perfusion, (2) Group B (n = 8) with collateralization via the circle of Willis, and (3) group C (n = 24) with leptomeningeal or ophthalmic artery collateral circulation. The rCPR values were significantly different in groups B and C with both methods, Xe-CT (P = 0.0035) and HMPAO-SPECT (P = 0.0014). rCPR was decreased in 13/14 group C patients investigated with Xe-CT and in 11/14 examined with HMPAO-SPECT. All patients in group B showed normal rCPR according to Xe-CT and HMPAO-SPECT. In group A, six of seven revealed decreased rCPR on Xe-CT, while rCPR values were normal in all four group A-patients examined with HMPAO-SPECT. The cerebral hemodynamics depend on a collateralization network and not only on the degree of internal carotid artery (ICA) stenosis. A decreased CPR in a vascular territory ipsilateral to an ICA stenosis or occlusion correlates strongly with the angiographic finding of leptomeningeal or ophthalmic artery collateral circulation.