Identifying regions of compromised hemodynamics in symptomatic carotid occlusion by cerebrovascular reactivity and oxygen extraction fraction

OBJECTIVES: Oxygen extraction fraction (OEF) and cerebrovascular reserve (CVR) are both proven predictors of stroke risk in symptomatic patients with carotid occlusion. Accordingly, hemispheric comparisons of CVR and OEF are significantly correlated. However, there was also substantial disagreement: hemispheres identified as compromised by CVR were normal by OEF. Our aim was to determine whether regional comparisons could resolve the CVR-OEF discordance. We also studied the relationship between white matter (WM) infarction and hemodynamic compromise.METHODS: Quantitative CVR and OEF were measured in 12 symptomatic patients with internal carotid artery occlusion. CVR and OEF comparisons were made in the anterior watershed (AWS), middle cerebral artery (MCA) and WM territories using various thresholds for hemodynamic compromise. Associations with WM infarction were also recorded.RESULTS: Comparison of CVR and OEF for the AWS and MCA showed high sensitivity (100%) with specificities of 83 and 40%, respectively. There was also agreement (k=Cohen's Kappa) for the AWS (k=0.83) and MCA (k=0.39) territories. CVR-OEF discordance was reduced with regional analysis. Hemodynamic compromise was more often found in patients with WM infarction.DISCUSSION: Regional comparison of CVR and OEF reduced the discordance compared with hemispheric analysis, especially for the AWS territory. Despite the persistence of some regions with compromised CVR and normal OEF, CVR is able to identify all regions with elevated OEF making it a useful screening technology. Future studies are needed to understand whether those remaining regions with compromised CVR are also at increased stroke risk despite normal OEF.     

PET OEF Reactivity for Hemodynamic Compromise in Occlusive Vascular Disease

Background and Purpose. Hemodynamic compromise in symptomatic patients with occlusive vascular disease (OVD) identified by cerebrovascular reserve (CVR) and oxygen extraction fraction (OEF) is an independent predictor of high stroke risk. However, up to 60% of patients compromised by CVR have normal OEF indicating a high rate of discordance. CVR is measured with an acetazolamide challenge, and OEF reactivity (OEFR) to acetazolamide, ie, a hemodynamic challenge, may reveal hemodynamic compromise and less discordance with measurements of CVR. Methods. Nine symptomatic patients with OVD were studied by positron emission tomography before and 15 minutes after 15 mg/kg intravenous acetazolamide in the middle cerebral artery territories of each hemisphere. Results. A close correlation between hemispheric CVR and OEFR was observed. Two hemispheres from two different patients showed an increase in OEF to acetazolamide challenge despite a normal baseline OEF. The two hemispheres showing an increase in OEF in response to acetazolamide were also associated with the lowest CVR and severest white matter hyperintensities. Conclusions. These observations suggest that positive OEFR may distinguish hemispheres in hemodynamic compromise despite normal OEF and show less discordance with CVR. However, these preliminary observations require confirmation in a larger study.     

Brain arteriolosclerosis and hemodynamic disturbance may induce leukoaraiosis

OBJECTIVE: To investigate whether internal carotid artery (ICA) occlusive disease-induced hemodynamic disturbance is associated with extensive white matter high-intensity lesions (WMLs) on T2-weighted MR images in the hemisphere with lacunar infarct in the basal ganglia. BACKGROUND: Hemodynamic disturbance in the brain with arteriolosclerosis may be one of the mechanisms by which ischemic injury induces extensive WMLs. METHODS: The authors used MRI and PET to study 21 patients with unilateral ICA occlusion or stenosis and lacunar infarct in the bilateral basal ganglia. In hemispheres with ICA disease, the association of WMLs with the mean hemispheric values of oxygen extraction fraction (OEF)-an index of hemodynamic compromise-measured with the 15O-labeled gas steady-state technique was analyzed. Twenty-five patients with ICA occlusive disease without lacunar infarct were studied as control subjects. RESULTS: In the hemispheres with ICA disease, patients with lacunar infarct had a significantly greater severity of WMLs than control subjects, although the mean hemispheric values of the OEF showed no significant difference. The severity of WMLs correlated significantly with the mean hemispheric values of the OEF in patients with lacunar infarct, but not in control subjects. Multivariate analysis revealed that lacunar infarcts and increased OEF were independent predictors of extensive WMLs, with lacunar infarcts the most heavily weighted factor. CONCLUSION: Internal carotid artery occlusive disease-induced hemodynamic disturbance is associated with extensive WMLs in hemispheres with lacunar infarct. Hemodynamic disturbance may contribute to the development of extensive WMLs, although brain arteriolosclerosis may be a major contributing factor.     

皮质下脑梗死所致血管性认知障碍患者认知功能与脑白质病变的相关性研究

目的 分析皮层下脑梗死所致血管性认知障碍 （subcorticalvascular cognitive impairment, SVCI） 脑白质 变性与认知功能评分的相关性。 方法 连续入组皮层下脑梗死患者91例, 根据神经心理学蒙特利尔认知评估 （Montreal Cognitive Assessment, MOCA） 分为皮层下脑梗死所致血管性认知障碍 （subcortical vascular cognitive impairment, SVCI） 组 （49例） 和无认知障碍的皮质下梗死 （subcortical infarcts, SI） 组 （42例） , 分析其临床、 认知 障碍、 神经影像学特征, 并探讨认知障碍与白质损伤的相关性。 结果 SVCI组糖尿病发病率高于SI组 （38.78% vs 16.67%, P =0.02） , SVCI组脑白质病变患者37 例 （75.51%） 。 脑白质损害程度与MOCA执行功能 （ Rs =-0.415, P =0.028） 、 瞬时记忆 （ Rs =-0.577, P =0.001） 、 注意 （ Rs =-0.382, P =0.001） 、 延迟记忆 （ Rs =-0.389, P =0.041） 等4个分量表以及MOCA 量表总分 （ Rs =-0.495, P =0.002） 成负相关。 结论 SVCI患者糖尿病比例高于SI患者, 白质病变多见, 且白质病变的程度可以反映不同程度的认知 损害。     

Compensatory mechanisms for chronic cerebral hypoperfusion in patients with carotid occlusion

BACKGROUND AND PURPOSE: The purpose of this experiment was to assess long-term cerebral hemodynamic and metabolic changes in patients with increased oxygen extraction fraction (OEF) in the hemisphere distal to an occluded carotid artery who remain free of stroke. Methods--Ten patients with increased OEF and no interval stroke underwent repeated positron emission tomography examinations 12 to 59 months after the initial examination. Quantitative regional measurements of cerebral blood flow, cerebral blood volume, cerebral rate of oxygen metabolism (CMRO2), and OEF were obtained. Regional measurements of the cerebral rate of glucose metabolism (CMRGlc) were made on follow-up in 5 patients. Statistical significance (P<0.05) was measured with t tests and linear regression analysis. RESULTS: The ipsilateral/contralateral OEF ratio declined from a mean of 1.16 to 1.08 (P=0.022). Greater reductions were seen with longer duration of follow-up (P=0.023, r=0.707). The cerebral blood flow ratio improved from 0.81 to 0.85 (P=0.021). No change in cerebral blood volume or CMRO2 was observed. CMRGlc was reduced in the ipsilateral hemisphere (P=0.001 compared with normal), but the CMRO2/CMRGlc ratio was normal. CONCLUSIONS: Increased OEF improves in patients with carotid occlusion and no interval stroke. This improvement in OEF is due to an improvement in collateral blood flow.     

Cerebral hemodynamics and risk for recurrent stroke in symptomatic internal carotid artery occlusion]

PURPOSE: In internal carotid artery occlusion, patients with inadequate blood supply relative to metabolic demand (misery perfusion) may be at increased risk for cerebral ischemia. This study investigated whether patients demonstrating misery perfusion on positron emission tomography (PET) have a high risk of subsequent stroke in symptomatic internal carotid artery occlusion. METHODS: We prospectively evaluated the relationship between the regional hemodynamic status of cerebral circulation and the subsequent risk of stroke in 40 patients with symptomatic internal carotid artery occlusion who underwent PET. Patients were divided into two hemodynamic categories according to the mean hemispheric value of oxygen extraction fraction (OEF) in the hemisphere supplied by the artery with symptomatic disease: patients with increased OEF and those with normal OEF. All patients were followed with medical treatment until the recurrence of stroke or death for 3 years. RESULTS: The three-year incidence of ipsilateral ischemic strokes for patients with normal OEF and those with increased OEF were 1 of 34 and 3 of 6 patients, respectively. A significantly higher incidence of ipsilateral strokes was found in patients with increased OEF (Kaplan-Meier analysis and log-rank test; p < 0.001). Multivariate analysis with the Cox proportional hazards model demonstrated that increased OEF significantly increased stroke recurrence: the relative risk was 19.5 (95% CI, 2.0-188.6) for ipsilateral stroke. An increase in the absolute OEF value was a better predictor of recurrent ischemic stroke than an OEF asymmetry. CONCLUSION: These findings suggest that patients with symptomatic internal carotid artery occlusion and misery perfusion have a high risk for subsequent stroke. Thus, identification and optimal treatment of patients with misery perfusion may be essential in preventing stroke.     

Selective neuronal damage and chronic hemodynamic cerebral ischemia

OBJECTIVE: In atherothrombotic internal carotid artery or middle cerebral artery (MCA) occlusive disease, chronic hemodynamic compromise may increase the risk for cerebral ischemic damage. To determine whether selective neuronal damage demonstrated as a decrease in central benzodiazepine receptor (BZR) in the normal-appearing cerebral cortex is associated with increased oxygen extraction fraction (OEF) (misery perfusion). METHODS: We measured BZR and OEF using positron emission tomography in 105 nondisabled patients with atherothrombotic internal carotid artery or MCA occlusive disease and no cortical infarction. By using three-dimensional stereotactic surface projections and the stereotactic extraction estimation method, without correction for partial volume effects, the abnormally decreased BZR index [(the extent of the pixels with Z-score more than 2 compared with controls) x (average Z-score in those pixels)] in the cerebral cortex of the MCA distribution with arterial disease was calculated, and it was found to be correlated with the mean hemispheric value of OEF and several clinical variables. RESULTS: All patients had pixels with abnormally decreased BZR, with the extent varying from 0.04 to 60.91%. Multivariate analysis showed that the abnormally decreased BZR index was positively correlated with the value of OEF and the history of stroke, whereas it was negatively correlated with the presence of hypercholesterolemia with statin treatment. Follow-up examinations of 17 patients without ischemic episode showed that a decrease of BZR was associated with an increase of OEF. INTERPRETATION: In atherothrombotic internal carotid artery or MCA occlusive disease, misery perfusion may cause selective neuronal damage, and statins might have beneficial effects against neuronal damage.     

Lack of correlation between pattern of collateralization and misery perfusion in patients with carotid occlusion

BACKGROUND AND PURPOSE: Misery perfusion, identified by increased oxygen extraction fraction (OEF), predicts subsequent stroke in patients with carotid occlusion. The purpose of this investigation was to determine the relationship of angiographic findings to increased OEF in these patients. METHODS: Forty-seven patients with carotid occlusion were studied with cerebral angiography and positron emission tomography (PET). The following angiographic data were collected blind to PET results: (1) pial collateralization, defined as retrograde filling of the MCA branches to the level of the insula; (2) presence of border zone shift; (3) presence of delayed venous phase; and (4) measurement of posterior communicating artery size. Patients were divided into 2 groups based on the PET measurement of normal or increased OEF. RESULTS: Seventeen of 47 patients had increased OEF distal to the occluded carotid artery. No significant relationship between increased OEF and any angiographic finding was found. Pial collateralization was present in only 2 patients, both with increased OEF (P=0.105). Border zone shift was equally distributed between the 2 groups (12 of 30 with normal OEF and 6 of 15 with increased OEF). Delayed venous phase was present in 4 patients, 3 of whom had increased OEF (P=0.073). The relationship between the size of the posterior communicating artery and OEF was not significant by linear regression analysis (P=0.242). CONCLUSIONS: With the possible but infrequent exceptions of delayed venous phase and pial collateralization, anatomic findings made on routine angiographic studies of patients with carotid occlusion do not correlate with increased OEF.     

Relationship Between Cerebral Vasomotor Reactivity and White Matter Lesions in Elderly Subjects Without Large Artery Occlusive Disease

BACKGROUND AND PURPOSE: The relationships between cerebral vasomotor reactivity (CVR) and white matter lesions (WMLs) were investigated mainly in patients with carotid stenosis. We aimed to study the relationship in asymptomatic elderly subjects without large artery occlusive disease. METHODS: A total of 33 elderly individuals (mean age was 76.2 years) who were free from neurological deficit or cognitive impairment were studied. Bilateral mean blood flow velocity was measured in the middle cerebral artery using a 2-MHz pulsed transcranial Doppler (TCD) system together with intravenous administration of acetazolamide as vasodilatory stimuli. WMLs on a fluid-attenuated inversion recovery (FLAIR) sequence of MRI were classified into two categories: subcortical deep white matter hyperintensity (SDWMH) and periventricular hyperintensity (PVH). The lesions in each category were then divided into three grades (grade 0-I, grade II, grade III) according to the Fazekas scale. RESULTS: CVR was inversely associated with the extent of SDWMH and PVH. The differences in CVR were statistically significant among different severity of WMLs: for SDWMH (70%+/- 10% in grade 0-I, 60%+/- 10% in grade II, and 40%+/- 10% in grade III, P < .001); for PVH (80%+/- 10% in grade 0-I, 60%+/- 10% in grade II, and 40%+/- 10% in grade III, P < .001). CONCLUSIONS: Impaired CVR is related to the extent of WMLs in asymptomatic elderly individuals without large artery stenosis. The findings in our study suggest that dysfunction of cerebral vascular autoregulation might be an important factor in the development of WMLs in the asymptomatic elderly without large artery occlusive disease.     

Benign prognosis of never-symptomatic carotid occlusion

OBJECTIVE: To determine the prognosis of asymptomatic carotid artery occlusion. BACKGROUND: As opposed to symptomatic carotid occlusion, little information is available on the prognosis of asymptomatic carotid occlusion. METHOD: Thirty never-symptomatic and 81 symptomatic patients with carotid occlusion underwent baseline assessment of 15 risk factors together with PET measurements of oxygen extraction fraction (OEF). Every 6-month telephone contact recorded interval medical treatment and subsequent stroke occurrence during an average follow-up of 32 months. Patients, treating physicians, and an end point adjudicator were blinded to PET results. RESULTS: Ischemic stroke occurred in 1 of 30 of never-symptomatic patients (3.3%) and 15 of 81 of symptomatic patients (18.5%; p = 0.03). No strokes in the carotid territory distal to the occluded vessel occurred in the never-symptomatic patients. Multivariate analysis of baseline risk factors for all 111 patients revealed that age, plasma fibrinogen level, and PET findings of high OEF distal to the occluded carotid artery were the only independent predictors of subsequent stroke (p < 0.05). Previous ipsilateral hemispheric or retinal symptoms was not a significant predictive variable. The lower risk of stroke in never-symptomatic patients was associated with a lower incidence of high OEF (4 of 30) as opposed to symptomatic patients (39 of 81; p = 0.002), but there was no significant difference in age or fibrinogen level. CONCLUSIONS: Never-symptomatic carotid occlusion carries a very low risk of subsequent ischemic stroke. This benign prognosis is associated with a low incidence of cerebral hemodynamic compromise in these patients. These data support further the importance of hemodynamic factors in the pathogenesis of ischemic stroke in patients with carotid occlusion.     

Reduced stroke risk in patients with compromised cerebral blood flow reactivity treated with superficial temporal artery to distal middle cerebral artery bypass surgery.

Extracranial-to-intracranial (EC-IC) bypass surgery for the prevention of stroke in patients with symptomatic carotid artery occlusion has nearly ended after a randomized trial showed no benefit of the procedure. Although an EC-IC bypass might benefit patients with compromised cerebrovascular hemodynamics, the randomized trial did not differentiate patients with hemodynamic from embolic etiologies. However, subsequent investigators have identified a subgroup of patients at increased stroke risk from hemodynamic compromise. Methods: We examined the subsequent stroke rate of 42 patients with symptomatic carotid occlusion at high risk for stroke identified as having a baseline cerebral blood flow (CBF)<45 mL/100 g/min and a >5% CBF reduction in one vascular territory after a vasodilatory challenge from 1 g of intravenous acetazolamide on stable xenon-computed tomography (CT) CBF imaging. Results: Thirty patients (group 1) treated medically were a subgroup with carotid occlusion from our long-term natural history study. During a median follow-up of 12 months, 9 patients (30%) had a new stroke within a median of 5 months. Twelve patients (group 2) had recurrent, disabling cerebral ischemic symptoms, with 8 progressing to mild fixed neurological deficits from deep white matter infarction identified on CT. All were treated with superficial temporal artery to distal middle cerebral artery (STA-MCA) bypass with restoration of cerebrovascular reserve postoperatively; none had a stroke during the 18-month minimum follow-up (P=.041). Perioperative morbidity included subendocardial infarction in one and a small, asymptomatic left frontal hemorrhage in another patient. Early postoperative and delayed xenon/CT CBF studies obtained a median of 5 months postoperatively showed maintenance of cerebrovascular reserve. Conclusion: STA-MCA bypass surgery can restore cerebrovascular reserve in high-risk patients with symptomatic internal carotid artery occlusion. This was achieved with minimal perioperative complications, resulting in a subsequent reduction of stroke frequency. We suggest that the efficacy of STA-MCA bypass surgery for symptomatic carotid occlusion be re-examined prospectively using hemodynamic selection criteria.     

Silent cortical neuronal damage in atherosclerotic disease of the major cerebral arteries

In atherosclerotic internal carotid artery (ICA) or middle cerebral artery (MCA) disease, hemodynamic compromise may cause selective neuronal damage manifested as loss of central benzodiazepine receptors (BZRs) in the normal-appearing cerebral cortex, without overt episode of stroke. To investigate the association of decreases in cortical BZRs with hemodynamic compromise and the effect of angiotensin receptor blockers (ARBs) on these receptors in patients whose atherosclerotic ICA or MCA disease is asymptomatic, we measured BZRs using positron emission tomography and ¹¹C-flumazenil in 79 patients with asymptomatic atherosclerotic ICA or MCA disease and no cortical infarction. Three-dimensional stereotactic surface projections were used to calculate the BZR index, a measure of abnormally decreased BZRs in the cerebral cortex within the MCA distribution. Multiple regression analysis showed this index to be positively correlated with the value of oxygen extraction fraction, with the presence of silent subcortical infarcts, and with the presence of ischemic heart disease, whereas it was negatively correlated with the treatment of hypertension with ARBs. In asymptomatic atherosclerotic ICA or MCA disease, hemodynamic compromise is associated with selective neuronal damage manifested as decreases in cortical BZRs in the noninfarcted cerebral cortex, whereas ARBs are associated with preservation of cortical BZRs.     

缺血性脑卒中患者动脉粥样硬化分布的临床研究

目的探讨急性缺血性脑卒中不同亚型与颈动脉粥样硬化分布的相关性。方法通过经颅多普勒超声(TCD)和颈动脉彩色多普勒血流成像(CDFI)方法检测颅内、外动脉粥样硬化程度,并结合病史、生化指标及影像学提示的病变部位进行综合分析。结果411例急性缺血性脑卒中患者,颅内动脉狭窄率为38.93%(160/411),颈动脉颅外段狭窄率24.09%(99/411)。颈动脉颅外段狭窄者年龄大、吸烟比例高,与无狭窄者比较差异有统计学意义(P=0.020,0.013);而颅内动脉狭窄者糖尿病发病率明显高于无狭窄者(P=0.005)。411例中皮质梗死49例、皮质下梗死108例、腔隙性梗死72例和短暂性脑缺血发作30例,颈动脉颅外段狭窄者以皮质梗死为主(P=0.001),并且动脉内-中膜层厚度明显增加(P=0.020);而颅内动脉狭窄者以腔隙性梗死更多见(P=0.016)。颅内、外动脉狭窄者的年龄、性别、血糖及血脂之间差异无统计学意义(均P>0.05)。结论临床和影像学检查所确定的急性缺血性脑卒中亚型与颅内、外动脉粥样硬化的病变部位相关,提示发病的原因可能不同。糖尿病与吸烟是引起颅内、外动脉病变的重要原因。     

MRI findings of small subcortical “lacunar-like” infarction resulting from large vessel disease

Small subcortical infarctions resulting from large-vessel disease are often observed. It is important to distinguish these from pure lacunar infarction resulting from small-vessel disease because the investigations and examinations differ. We investigated the differences on brain magnetic resonance imaging (MRI) between small subcortical "lacunar-like" infarcts resulting from large-vessel disease and pure lacunar infarcts. Thirteen subjects with small lacunar-like infarcts (size < 2 cm), resulting from large-vessel disease, and 30 subjects with lacunar infarcts (< 2 cm), without large-vessel disease were studied. We measured infarction size using a 1.5-T MRI device and evaluated silent subcortical hyperintensity lesions using the modified Scheltens' score. Large-vessel lesion was confirmed by conventional angiography, duplex carotid scan, and magnetic resonance angiography. There was no difference in the mean age of the two groups. Cerebrovascular risk factors and atherosclerotic complications were also comparable for the two groups. Progressive stroke was more common in the lacunar-like infarction group than in the lacunar infarction group (P = 0.004). Scores for periventricular hyperintensity, white matter hyperintensity, basal ganglia hyperintensity, and total subcortical hyperintensity scores were significantly higher in the lacunar infarction group than in the lacunar-like infarction group. The difference in basal ganglia hyperintensity scores was remarkable (P = 0.001). The enlargement of the perivascular space was also significantly greater in the lacunar infarction group than in the lacunar-like infarction group. These findings seem to reflect differences in the pathogenesis of infarction between the two groups. Silent subcortical hyperintensity lesions and enlargement of perivascular space are useful for between distinguishing small lacunar-like infarct resulting from large-vessel disease and pure lacunar infarction. This may have significant implications for the management of patients with lacunar-sized infarctions. It suggests that the pathogenesis of lacunar-sized infarction is variable.     

脑梗死急性期梗死部位及白质病变与认知功能关系的临床分析

【摘要】
目的 研究急性脑梗死患者梗死部位及是否合并脑白质病变对患者早期认知功能的影响。
方法 采用临床痴呆评定量表、简易精神状态检查量表和中文版蒙特利尔认知评估量表对连续入组的急性脑梗死患者进行认知心理学评估,分析患者不同梗死部位包括皮层梗死、皮层下关键部位梗死和皮层下非关键部位梗死及是否合并白质病变对患者认知功能的影响。
结果 急性脑梗死患者血管性认知功能障碍组的平均年龄显著高于无认知功能障碍组（67.31 10.88 vs 57.09 9.91,P=0.015）,神经功能缺损评分显著高于无认知功能障碍组［3.0（2.0～4.0） vs 1.0（1.0～2.0）,P=0.012］。认知功能障碍组的日常生活能力评分显著低于无认知功能障碍组（81.67 23.55 vs 95.91 12.00,P=0.029）。两组患者梗死部位有显著差异（P=0.042）,皮层梗死更多见于血管性认知功能障碍组,皮层梗死患者的视空间与执行功能显著低于皮层下非关键位置梗死患者［1.5（0.0～3.0） vs 3.0（2.0～4.0）,P=0.016］。白质病变与认知障碍的发生无明显相关性。
结论 急性脑梗死患者早期认知障碍与年龄、严重的神经功能缺损、皮层梗死、日常生活能力下降密切相关。     

儿童缺血型烟雾病的临床和影像分析

【摘要】
目的 分析儿童缺血型烟雾病患者的临床和影像特点,探讨脑梗死的相关因素。
方法 回顾性分析2011年6月～2012年6月收治的27例儿童缺血型烟雾病患者的临床及影像学资料。
大脑半球分为无脑梗死半球32侧和脑梗死半球22侧,将患者性别、年龄、造影特点（包括54侧半球
的Suzuki分期、大脑后动脉分期,眼动脉、颞浅动脉、脑膜动脉、枕动脉、上颌动脉和后循环向前循
环代偿）与脑梗死的发生进行统计分析。
结果 27例患者的临床资料显示性别和年龄与脑梗死的发生差异不具有显著性（性别χ2=2.095,
P =0.148;年龄χ2=4.286,P =0.453）。根据半球计算：皮质脑梗死17侧（17/22）,额叶梗死14侧
（14/22）,皮质下脑梗死9侧（9/22）。无梗死侧半球和梗死侧半球Suzuki分期以及大脑后动脉分期
的差异具有显著性（Suzuki分期Z=－3.054,P =0.002;大脑后动脉分期Z=－4.557,P <0.001）。眼动脉、
颞浅动脉、脑膜动脉、枕动脉、上颌动脉和后循环向前循环代偿与脑梗死的发生差异不具有显著性。
结论 本研究显示儿童缺血型烟雾病皮质脑梗死较皮质下脑梗死常见。在皮质脑梗死中,额叶脑
梗死最常见。脑梗死的发生与Suzuki分期和大脑后动脉受累程度有关。     

Carotid atherosclerosis and cerebral white matter lesions in a population based magnetic resonance imaging study

Cerebral white matter lesions are frequently observed on magnetic resonance imaging of elderly, nondemented persons. There is evidence that white matter lesions are involved in the pathophysiology of cognitive decline and dementia. White matter lesions can be divided into those in the periventricular and those in the subcortical region. Pathological and epidemiological studies suggest that atherosclerosis is involved in the pathogenesis of these lesions. Our study reports on the association between atherosclerosis in the carotid arteries and white matter lesions in a population-based study among 1077 elderly subjects. We randomly sampled 1077 subjects aged between 60–90 years from two prospective population-based studies. All subjects underwent ultrasonography of the carotid artery. In addition, 1.5 T magnetic resonance imaging was performed; white matter lesions in the subcortical and periventricular regions were rated separately. With increasing number of plaques in the carotid artery the severity of periventricular white matter lesions increased (P _trend = 0.03), but not the severity of subcortical white matter lesions (P _trend = 0.19). In addition, an increase in intima media thickness was borderline significantly associated with an increased severity of periventricular white matter lesions (P _trend = 0.09), but not of subcortical white matter lesions (P _trend = 0.68). These findings suggest that partly dissimilar pathogenetic mechanisms are involved in the etiology of periventricular and subcortical white matter lesions. Received: 13 January 1999/Received in revised form: /15 November 1999/Accepted: 17 December 1999     

Cerebrovascular reserve capacity

Cerebrovascular reserve capacity (CVR) describes how far cerebral perfusion can increase from a baseline value after stimulation. Measurement of cerebral blood flow (CBF) can be done by PET or SPECT. Noninvasive and easily performed transcranial Doppler sonography (TCD) is mostly used as indirect perfusion measurement. Stimulation of cerebral perfusion is often done by CO2 inhalation or acetazolamide injection. Alternative stimuli are breath holding or cerebral activation by hand-gripping. Normal values for these tests are presented. The hemodynamic effect of stenoses of the internal carotid artery (ICA) can be estimated using CVR. The relevance of CVR is discussed controversially, since cerebral infarction due to stenosis of arteries supplying the brain is probably mostly of embolic, not hemodynamic origin. The indication for carotid artery surgery according the NASCET and ECST investigations takes into account only the degree of the stenoses and not the CVR. According to recent studies, the risk of cerebral infarction in these patients is considerably higher with reduced CVR. Therefore, CVR can be used as an additional parameter if the indication for surgery is not defined, especially in asymptomatic carotid artery stenosis. It seems also possible to identify patients who might profit from an extra-intracranial bypass operation and high-risk patients for cerebral ischemia with cerebral microangiopathy. Furthermore, the risk of cerebral infarction during carotid artery surgery and also during heart surgery can be estimated using CVR. More studies with a higher number of patients are needed to confirm the potential predictive diagnostic value of CVR in order to establish CVR measurement as part of a routine diagnostic neuroangiologic program.     

Detection of hemodynamic impairment on 15O gas PET using visual assessment of arterial spin-labeling MR imaging in patients with moyamoya disease

It is unclear whether the visual assessment of noninvasive arterial spin labeling magnetic resonance imaging (ASL) can identify instances of hemodynamic compromise including an elevated oxygen extraction fraction (OEF) measured by ¹⁵O-gas positron emission tomography (PET). Here we evaluated the relationship between a four-point visual assessment system referred to as 'ASL scores' using ASL with two postlabeling delays (PLDs; 1525 ms and 2525 ms) and some quantitative hemodynamic parameters measured by PET. We retrospectively evaluated the cases of 18 Japanese patients with moyamoya disease who underwent ASL and PET. We compared the patients' regional ASL scores on two ASL images to the regional values of PET parameters, and we observed a significant trend in accord with the presumed clinical severity among all PET parameters and ASL scores (p < .003). The ASL score of the long PLD (2525 ms) showed the highest specificity (98.5%) for elevated OEF. Our results suggest that hemodynamic impairment (including elevated OEF) in patients with moyamoya disease may be grossly assessed by a visual assessment of noninvasive ASL images, which can be easily obtained in clinical settings.     

A new model of white matter injury in neonatal rats with bilateral carotid artery occlusion

Periventricular leukomalacia is an important cause of cerebral palsy and characterized by cysts and coagulation necrosis in the periventricular white matter. Since no model of periventricular leukomalacia has been established in small animals, it is expected to establish a new model of white matter injury in immature rodents. Bilateral carotid arteries were occluded in neonatal rats at 5 days of age, and the brain neuropathologically examined at 7 days of age. Among 22 brains histologically examined, 20 (90.9%) had white matter changes including coagulation necrosis and cystic lesions in and around the internal capsule, while only two had small cerebral infarction and five showed some ischemic neurons in the cerebral cortex. Cerebral blood flow (CBF) decreased to about 25% of controls in the subcortical white matter in the animals with bilateral carotid artery occlusion (BCAO). Amyloid precursor protein (APP) immunohistochemistry demonstrated various APP-immunoreactive axonal profiles in the internal capsule and the subcortical white matter, and stronger expression of APP in pyramidal neurons in the cerebral cortex of BCAO brains. These results indicated that the white matter is more vulnerable than the cerebral cortex in 5-day-old rats when CBF decreases to about 25% and suggested that this model is useful for investigating the white matter changes induced by cerebral hypoperfusion in the neonatal brain, since previous models of hypoxic-ischemic brain injury in neonatal mice and rats revealed preferential susceptibility of the gray matter. It was also indicated that APP is a sensitive marker for mild axonal disruption in the white matter of the immature brain.