Preoperative Central Benzodiazepine Receptor Binding Potential and Cerebral Blood Flow Images on SPECT Predict Development of New Cerebral Ischemic Events and Cerebral Hyperperfusion After Carotid Endarterectomy

Risk factors for cerebrovascular complications developing during or after carotid endarterectomy (CEA) include preoperative impairments in cerebral hemodynamics, as detected by the demonstration of decreased cerebrovascular reactivity (CVR) to acetazolamide on brain perfusion SPECT. Central benzodiazepine receptor binding potential (CBRBP) and cerebral blood flow (CBF) images on SPECT provide high sensitivity and high specificity for detecting misery perfusion in patients with chronic unilateral major cerebral artery occlusive disease. The aim of the present study was to determine whether preoperative CBRBP/CBF images on SPECT could identify patients at risk for new cerebral ischemic events, including neurologic deficits and cerebral ischemic lesions on diffusionweighted MRI, or cerebral hyperperfusion after CEA and to compare the predictive accuracy of CBRBP/CBF with that of CVR to acetazolamide on SPECT. Methods: CBF, CVR, and CBRBP were assessed using N-isopropyl-p- 123 I-iodoamphetamine ( 123 I-IMP) and 123 I-iomazenil SPECT before CEA in 112 patients with unilateral internal carotid artery stenosis ($70%). CBF measurement using 123 I-IMP SPECT was also performed immediately and 3 d after CEA. A region of interest was automatically placed in the middle cerebral artery territory in both cerebral hemispheres using a 3-dimensional stereotactic region-of-interest template. Diffusion-weighted MRI was performed within 3 d before and 24 h after surgery. Results: A preoperative increase in the affected side–to–contralateral side asymmetry on CBRBP/CBF value was the only significant independent predictor of postoperative new cerebral ischemic events (95% confidence intervals [CI], 1.145–1.608; P 5 0.0004) or post-CEA hyperperfusion (95% CI, 1.244–2.252; P 5 0.0007). There was no difference in the ability to predict post-CEA hyperperfusion when comparing the area under the receiver-operating-characteristic curve of the affected side–to– contralateral side asymmetry on CBRBP/CBF and that of the CVR in the affected hemisphere. However, the former value (0.924; 95% CI, 0.854–0.972) was significantly greater than the latter value (0.782; 95% CI, 0.697–0.852) for the prediction of new postoperative cerebral ischemic events (P , 0.05). Conclusion: Preoperative CBRBP/CBF images on SPECT can more accurately identify patients at risk for cerebrovascular complications occurring during or after CEA when compared with preoperative CVR to acetazolamide.