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Assessing collateral cerebral perfusion with technetium-99m-HMPAO SPECT during temporary internal carotid artery
C J Palestro1, C Sen, M Muzinic
1Division of Nuclear Medicine, Long Island Jewish Medical Center, New Hyde Park, NY 11042.
Insights
Assessing cerebral blood flow during temporary carotid artery occlusion using 99mTc-HMPAO SPECT helps predict tolerance. Symmetric perfusion indicates safety, while decreased perfusion may signal risks for stroke after internal carotid artery occlusion.
Area of Science:
- Neurology
- Radiology
- Neurosurgery
Background:
- Cerebral infarction after internal carotid artery occlusion stems from embolism or poor collateral flow.
- Assessing collateral circulation is challenging, with limited utility of traditional methods like angiography and stump pressures.
- Advanced imaging techniques are often unavailable or not yet established.
Purpose of the Study:
- To evaluate the utility of 99mTc-HMPAO SPECT during temporary internal carotid artery occlusion for predicting tolerance.
- To identify patients at risk for postocclusion complications based on cerebral perfusion patterns.
Main Methods:
- 99mTc-HMPAO SPECT imaging was performed during temporary carotid artery occlusion in 20 patients.
- Patients were assessed for cerebral perfusion symmetry and underwent subsequent carotid artery procedures.
- Outcomes including complications and neurological deficits were recorded.
Main Results:
- Fourteen patients showed symmetric cerebral perfusion and tolerated occlusion (11 transient, 3 permanent).
- Five patients had globally decreased perfusion; one underwent transient occlusion, one carotid sacrifice without bypass, both without sequelae.
- Three patients with decreased perfusion underwent bypass grafting prior to sacrifice. One patient with a focal defect and no bypass developed deficits.
Conclusions:
- Symmetric cerebral perfusion during temporary occlusion suggests internal carotid artery occlusion is well-tolerated.
- Abnormal perfusion patterns, even if not fully understood, identify patients at risk for complications, guiding neurosurgical management.
- 99mTc-HMPAO SPECT offers a valuable tool for pre-procedural risk assessment in carotid artery interventions.
Abstract:
Cerebral infarction following internal carotid artery occlusion results from either embolism or inadequate collateral blood flow. Although risk of embolism can be minimized, detecting compromised collateral circulation is more difficult. Cerebral angiography, carotid stump pressures and clinical evaluation during internal carotid artery occlusion are of limited utility. Xenon-133 radionuclide studies and stable xenon computed tomography are not readily available. We evaluated 99mTc-HMPAO SPECT, during temporary carotid artery occlusion, in 20 patients considered for internal carotid artery occlusion. Fourteen demonstrated symmetric cerebral perfusion during occlusion; eleven underwent transient and three had permanent carotid artery occlusion without complications. Five patients had ipsilateral globally decreased perfusion during temporary occlusion. One patient underwent transient occlusion of this vessel and one underwent carotid sacrifice without bypass grafting; both recovered without sequelae. The three remaining patients underwent carotid artery bypass grafting prior to sacrifice of this vessel. One patient with a small focal perfusion defect underwent carotid artery sacrifice without bypass grafting and developed acute neurologic deficits postoperatively. These initial results suggest that symmetric cerebral perfusion during temporary occlusion indicates that internal carotid artery occlusion will be tolerated. Although its implications are not yet well defined, the abnormal study identifies patients potentially at risk for postocclusion complications, thus providing a basis for neurosurgical management.