| PURPOSE:To investigatet the diagnostic value of computed tomography perfusion (CTP) in patients who had unilateral middle cerebral artery (MCA) and carotid artery stenosis or occlusion, combining with CT angiography (CTA) and digital subtraction angiograph (DSA) to evaluate the relationship between findings of CTP and the degree of MCA stenosis. In patients with unilateral carotid artery occlusion (CAO), we investigate hemodynamic parameter and to evaluate whether patients with secondary in addition to primary pathways have a worse hemodynamic state of the brain than those without secondary pathways. We also assess the utility of CTP for evaluating cerebral hemodynamic changes before and after interventional therapy in patients with unilateral ICA/MCA high-grade stenosis.METHODS:1. Eighty-nine patients with MCA steno-occlusion were classified into three groups according to the severity of the stenosis. Mean values(CBF,CBV,TTP) and the affected-to-contralateral ratio (rCBF,rCBV,rTTP) of CTP parameters were measured and compared to evaluate the cerebral hemodynamics and its relationship with the degree of stenosis, respectively. Furthermore, the circle of Willis and collateral pathways were investigated.2. Thirty-eight patients with unilateral CAO underwent CTP and DSA.The CBF,CBV,and TTP absolute values of both hemispheres were measured. We then calculated the CBF,CBV and TTP ratios (rCBF,rCBV,rTTP) by dividing the mean values on the affected side by the mean values on the contralateral side. Two-tailed paired t tests were used to compare the mean perfusion parameter values in affected hemispheres with those in contralateral hemispheres. Wilcoxon rank sum test were used to compare the difference of the rCBF,rCBV,and rTTP between patients with and without secondary collateral.3. Twenty-two patients with unilateral ICA/MCA high-grade stenosis underwent percutaneous transluminal angioplasty and stent (PTAS). CTP was performed before and one week after the stent-placement procedure. The CBF,CBV,and TTP values were measured and compare the difference by two-tailed paired t tests. The rCBF,rCBV and rTTP before and after therapy were evaluated and comparied by two-tailed paired t tests and Wilconxon signed-rank test.RESULTS:1. In Groupâ… , there were no significant differences in the values between the affected and contralateral sides. In Groupâ…¡, CBF values remained stable and CBV values increased slightly with increasing degrees of stenosis, but showed no significant difference between the two sides; however, TTP values significantly increased in the affected hemispheres (t=2.83,P<0.05). In Groupâ…¢, CBF values also remained stable and showed no significant difference between the affected hemispheres and the contralateral hemispheres, but CBV and TTP values were significantly increased in the affected hemispheres compared with the contralateral hemispheres (CBV:t=6.04,P<0.01; TTP:t=13.18,P<0.01). The rTTP was significantly correlated with the degree of stenosis (r=0.713, P<.01), whereas the CBV ratio was weakly correlated with the degree of stenosis (r=0.365, P <.01). In addition, Patients with an abnormal circle of Willis and multiple cerebrovascular stenosis lesions had marked increase in the rTTP, which aggravated the impairment of hemodynamics.2. In 38 patients with unilateral CAO, the CBF values remained stable and there were no significant differences in the values between the affected and contralateral sides (t=1.08,P=0.285). CBV and TTP values were significantly increased in the affected hemispheres compared with the contralateral hemispheres (CBV:t=5.27,P<0.01; TTP: t=10.11,P<0.01). The radio of CBV and TTP were significantly higher in patients with secondary collaterals than in patients with only primary collaterals (CBV:Z=2.32,p=0.020<0.05; TTP:Z=4.50,p<.001). The presence of any second collateral flow was associated with increased CBV and TTP ipsilateral to the occlusion in comparison with patients without second collateral flow.3. Before operation, there was significant heterogeneity of cerebral hemodynamics in patients with a unilateral ICA/MCA high-grade stenosis, with stable CBF value and increased CBV and TTP value in the hemisphere ipsilateral to the occlusion(CBV: t=2.10,P=0.048;TTP:t=4.83,P<0.000). After operation, a significant normalization of the perfusion parameters was observed after the stent-placement procedure, there were no significant differences in the CBV and TTP values between the affected and contralateral sides(CBV:t=0.34,P=0.737; TTP:t=0.80,P=0.432). In addition, there was statistically significant difference between the values of rCBV and rTTP before and after therapy (rCBV:t=2.22 P=0.038; rTTP:S=126.5 P<0.0001).CONCLUSIONS:1. CTP and angiography measurement provided an effective way to evaluate hemodynamics and angiographic data in patients with unilateral chronic MCA steno-occlusion. Most patients have stable hemodynamic constitutions, but those with multiple steno-occlusive lesions and an abnormal circle of Willis could have increased risk of ischemic events.2. There was significant heterogeneity of cerebral hemodynamics in patients with a unilateral CAO, with stable CBF value and increased CBV and TTP value in the hemisphere ipsilateral to the occlusion. In addition, the patterns of collateral pathways are important factors determining the severity of haemodynamic impairment. The presence of any second collateral flow was associated with serious impaired cerebral hemodynamics in comparison with patients without second collateral flow.3. CTP is a useful technique for the assessment of the hemodynamic modifications in patients with unilateral ICA/MCA high-grade stenosis. The quantitative evaluation of cerebral perfusion makes it are liable tool for the follow-up of patients who undergo PTAS. |
PDF Full Text Request