Brain perfusion SPECT imaging and acetazolamide challenge in vascular cognitive impairment

Cerebrovascular disease is recognized as a common cause of cognitive impairment and dementia, alone or coexisting with other neurodegenerative diseases, mostly Alzheimer's disease. Vascular cognitive impairment (VCI) is a part of the heterogenous disorders group related to cerebral vessel disease. Although age is one of the most important risk factors for VCI, other common cardiovascular risk factors are also involved. By investigating these risk factors, a high proportion of these cognitive disorders can be prevented and/or delayed. Until now, only treatment of midlife arterial hypertension has been recognized as a preventing factor of vascular dementia. Brain MRI is becoming the method of choice to investigate cerebral vascular pathologies. However, this form of morphological imaging remains inadequate and does not provide useful functional information during VCI exploration, despite which functional imaging such as brain perfusion single-photon computed tomography, performed in baseline conditions and/or after an acetazolamide challenge, is underutilized in VCI exploration. The common strategies for VCI screening have not been standardized until now, and therefore further long-term imaging studies are needed to establish early diagnostic protocols. The present review summarizes the potential benefits of brain perfusion single-photon computed tomography imaging and possible scintigraphic quantification of cerebral hemodynamic reserves in investigation of VCI.     

Comparison study of positron emission tomography, X-ray CT and MRI in parkinsonism with dementia

In cases of Parkinson's disease, a high incidence of dementia and simultaneous pathologic changes of Alzheimer's type have been reported. X-ray CT and MRI have such good spatial resolution that they can be expected to be useful for evaluation of brain atrophy. Positron emission tomography (PET) used with 18F-2-deoxy-2-fluoro-D-glucose is considered to reflect regional function. By these techniques, brain atrophy and local cerebral metabolic rate of glucose (LCMR-glc) in patients with Parkinsonism with dementia was studied, and also compared with age-matched normal controls and senile dementia of Alzheimer type. In seven cases of Parkinson's disease with dementia, LCMRs-glc were statistically decreased in all regions in comparison with ten normal controls. LCMRs-glc in six Parkinson's disease without dementia were higher than those of demented Parkinson's disease, but significantly lower than normal controls in all regions except basal ganglia. Some aged normal controls presented cortical atrophy and a significant difference could not be seen in evaluation by MRI among these three groups. There was also no correlation between LCMR-glc and cortical atrophy. There was no significant difference of LCMR-glc between six Guamnian cases of Parkinsonism-Dementia complex (PD complex) without ALS and four cases of PD complex with ALS, and these values were significantly lower than five Guamanian and ten Caucasian normal controls. In PD complex with and without ALS, remarkable cortical atrophy and ventricular dilatation were recorded in comparison with normal controls, and correlation between decrement of LCMR-glc and cortical atrophy was indicated in frontal, parietal and temporal lobe. In Parkinson's disease with dementia and PD complex in Guam, LCMRs-glc in all regions of brain were generally lower than normal controls. These findings were different from Alzheimer's disease in which LCMR-glc have been reported to be low especially in cerebral cortex. On the other hand, cortical atrophy and ventricular dilatation evaluated by MRI and CT was apparent in PD complex, but these changes were not remarkable in Parkinson's disease. Cortical atrophy did not always correlate with the decrease of LCMR-glc and changes of LCMR-glc could reflect clinical signs such as Parkinsonism and dementia. Both PET as a functional imaging method and MRI, CT as an anatomical imaging method are useful to access the study of these diseases.     

Subcortical ischemic vascular dementia: assessment with quantitative MR imaging and 1H MR spectroscopy

BACKGROUND AND PURPOSE: Subcortical ischemic vascular dementia is associated with cortical hypometabolism and hypoperfusion, and this reduced cortical metabolism or blood flow can be detected with functional imaging such as positron emission tomography. The aim of this study was to characterize, by means of MR imaging and 1H MR spectroscopy, the structural and metabolic brain changes that occur among patients with subcortical ischemic vascular dementia compared with those of elderly control volunteers and patients with Alzheimer's disease. METHODS: Patients with dementia and lacunes (n = 11), cognitive impairment and lacunes (n = 14), and dementia without lacunes (n = 18) and healthy age-matched control volunteers (n = 20) underwent MR imaging and 1H MR spectroscopy. 1H MR spectroscopy data were coanalyzed with coregistered segmented MR images to account for atrophy and tissue composition. RESULTS: Compared with healthy control volunteers, patients with dementia and lacunes had 11.74% lower N-acetylaspartate/creatine ratios (NAA/Cr) (P = .007) and 10.25% lower N-acetylaspartate measurements (NAA) in the cerebral cortex (P = .03). In white matter, patients with dementia and lacunes showed a 10.56% NAA/Cr reduction (P = .01) and a 12.64% NAA reduction (P = .04) compared with control subjects. NAA in the frontal cortex was negatively correlated with the volume of white matter signal hyperintensity among patients with cognitive impairment and lacunes (P = .002). Patients with dementia, but not patients with dementia and lacunes, showed a 10.33% NAA/Cr decrease (P = .02) in the hippocampus compared with healthy control volunteers. CONCLUSION: Patients with dementia and lacunes have reduced NAA and NAA/Cr in both cortical and white matter regions. Cortical changes may result from cortical ischemia/infarction, retrograde or trans-synaptic injury (or both) secondary to subcortical neuronal loss, or concurrent Alzheimer's pathologic abnormalities. Cortical derangement may contribute to dementia among patients with subcortical infarction.     

血管性痴呆的MRI定量研究

目的 寻找可预测血管性痴呆（ｖａｓｃｕｌａｒ ｄｅｍｅｎｔｉａ,Ｖａｌ）的神经影像学指标。方法 对３０例ＶａＤ和３０名中风后非痴呆（ｓｔｒｏｋｅ ｗｉｔｈｏｕｔ ｄｅｍｅｎｔｉａ,ＳＷＤ）患者进行ＭＲＩ测量研究,测量指标包括：大脑白质病变面积、脑梗死面积、脑室－脑比率和正中矢状面胼胝体面积与幕上颅腔面积比率,并分析脑梗死所在部位。用判别分析法寻找区分ＶａＤ与ＳＷＤ的测量指标。结果 小血管病和多发脑     

非痴呆型血管性认知功能障碍的结构及功能磁共振研究进展

非痴呆性血管性认知功能障碍（VCIND）处于血管性认知功能障碍（VCI）的早期阶段,血管性认知功能障碍是由血管性因素导致的从轻度认知功能障碍到痴呆的一类综合征.已有研究表明VCIND是可以逆转的,所以对其早期干预,有着重要的社会意义.近年来,随着功能磁共振的研究与应用,对脑结构和脑网络的研究也越来越受到关注,一些磁共振新技术如磁共振扩散张量成像（DTI）和功能磁共振也应运而生,因其易操作性和无创性,且能够在体研究脑结构及脑功能方面的改变,使其越来越具有研究VCIND的生理病理机制的潜在性,本文就其在VCIND方面的研究进展进行综述.     

多模态功能MRI对血管性认知障碍的研究进展

血管性认知障碍(VCI)目前已成为继阿尔茨海默病之后的全球第二大认知障碍类型。利用功能MRI对VCI病人的脑形态和功能进行评价,有利于VCI的早期诊断、治疗和预后评估,同时也对揭示VCI病程演变中病理特征的改变、神经功能预测、行为改变等具有重要意义。综述多模态功能MRI对VCI的研究现状,阐明该技术对探究脑形态、功能与血管性认知改变间关系的作用,为寻求VCI早期诊断的影像诊断标准提供思路。     

脑微出血的磁共振检查与临床意义

脑微出血是重要的小血管病影像学标志,磁共振技术的进步使得越来越多的脑微出血被检出,微出血的发现对潜在的小血管病诊断、抗血栓药物的使用、症状性脑内出血、认知障碍和痴呆都有重要意义。作者根据最新文献就在不同疾病条件下微出血的磁共振检测和临床意义作一综述。     

~(18)F-FDGPET显像诊断老年性痴呆初步研究

目的　探讨18F 脱氧葡萄糖 (FDG)PET显像诊断老年性痴呆 (AD)的影像特征和诊断标准。方法　静脉注射18F FDG后行脑断层显像 ,获得顶叶、颞叶、额叶单位面积放射性计数与小脑计数的比值 ,以此作为半定量指标。结果　 12例正常人可见大脑皮质各叶、基底神经节、丘脑及小脑放射性分布均匀对称。 12例AD影像分为 3种 :双侧顶叶放射性减低 5例 ,双侧颞顶叶减低 4例 ,单侧颞顶叶减低 3例。半定量分析显示AD患者顶颞叶代谢显著低于正常人 ,并与痴呆程度相关。 11例非AD痴呆影像也分 3种 :多发性非对称性放射性减低 8例 ,双侧颞顶叶伴其他多灶性放射性减低 2例 ,显像正常 1例。MRI检查 10例AD可见颞叶、杏仁核、海马体积缩小 ;2例轻度AD虽有代谢减低 ,但MRI未见海马体积缩小。 10例非AD痴呆MRI可见脑内陈旧出血、梗死、软化灶等病灶 ,而这些表现AD患者未见到。结论　在MRI除外脑内结构损害病灶基础上 ,18F FDGPET发现双侧或单侧顶叶或颞顶叶代谢减低可诊断AD ;半定量分析有助于痴呆程度的评价。     

Differential diagnosis of bilateral parietal abnormalities in I-123 IMP SPECT imaging

This report discusses the clinical significance of bilateral parietal abnormalities on I-123 IMP SPECT imaging in 158 patients with cerebral disorders. This pattern was seen in 15 out of 21 patients with Alzheimer's disease; it was also seen in 4 out of 5 patients with Parkinson's disease with dementia, in 3 out of 17 patients with vascular dementia, in 1 out of 36 patients with cerebral infarction without dementia, in 1 out of 2 patients with hypoglycemia, and in 1 out of 2 patients with CO intoxication. Detection of bilateral parietal abnormalities is a useful finding in the diagnosis of Alzheimer's disease, but one should keep in mind that other cerebral disorders may also show a similar pattern with I-123 IMP SPECT imaging.     

Predictors of patient response to pulmonary thromboendarterectomy

OBJECTIVE: We sought to identify imaging features that help predict surgical success in patients undergoing thromboendarterectomy. MATERIALS AND METHODS: Thirty-nine consecutive patients who underwent pulmonary angiography and thromboendarterectomy during 1995 and 1996 were included. Thirty-four underwent helical CT angiography. Measurements of postoperative pulmonary vascular resistance were compared with preoperative imaging features and preoperative pulmonary vascular resistance. RESULTS: The best imaging indicators of a relatively high postoperative pulmonary vascular resistance were the extent of small vessel disease identified on CT angiograms as segments with abnormal perfusion but normal segmental arteries (p = 0.005) and the extent of central disease (p = 0.015). Combined with preoperative pulmonary vascular resistance, these features had a strong correlation with postoperative outcome (p = 0.0005). Segmental arterial disease seen on both conventional angiography and CT angiography correlated poorly with surgical outcome. CONCLUSION: In patients with chronic thromboembolic pulmonary hypertension, CT angiographic evidence of extensive central vessel disease and limited small vessel involvement indicates a favorable surgical outcome.     

Cognition and 99Tcm-HMPAO SPECT in Parkinson's disease.

99Tcm-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) of brain was performed in 43 unselected patients with Parkinson's disease to evaluate whether low cerebral perfusion on SPECT correlated with cognitive impairment in the patients. All patients received neurological, Mini-Mental State Examination and a neuropsychological assessment. Eighteen (41.9%) of the 43 patients were demented. Thirty patients (69.8%) had abnormal SPECT: 17 had perfusion defects in cortical regions, eight in basal ganglia and five in both regions. Of the 22 patients with abnormal cortical perfusion, 15 (68.2%) were demented; only three (14.3%) of the 21 patients without cortical defect were demented (P < 0.01). Twelve of the 15 demented patients had low perfusion in the parietal region alone or in parietal and occipital regions. The cortical perfusion defects, present in 22 (51.2%) Parkinson's patients, are highly correlated with cognitive impairment. The pattern of SPECT abnormality in most demented patients with Parkinson's disease is similar to that seen in Alzheimer's disease, suggesting that the underlying pathophysiology for dementia in patients with Parkinson's disease may be similar to that in Alzheimer's disease.     

Semi-automatic quantification of regional cerebral perfusion in primary degenerative dementia using 99m technetium-hexamethylpropylene amine oxime and single photon emission tomography

A new semi-automatic method for quantifying regional cerebral uptake of 99m technetium-hexamethylpropylene amine oxime (99mTc-HMPAO) was used to assess single photon emission tomograms from 5 normal subjects, 14 patients with Alzheimer's disease, 14 patients with dementia of frontal lobe type and 4 patients with dementia with motor neurone disease. Uptake in both posterior cortical regions, although not in other regions, was significantly lower (P less than 0.05) in Alzheimer's disease than in normal controls. Conversely in both dementia of frontal lobe type and dementia with motor neurone disease, uptake was significantly reduced (P less than 0.05) compared with controls in all anterior cortical regions but not in posterior regions. Numerical findings in each disease mirrored the pattern of reduced tracer uptake previously reported by visual assessment. Nine patients were re-examined after an interval of at least 1 year. Comparison of follow-up scans with original images showed significant decreases in mid-anterior, left anterior and left posterior cortical uptake (P less than 0.01) in patients with Alzheimer's disease and in left middle, left posterior and right posterior cortical uptake (P less than 0.01) in patients with dementia of frontal lobe type. The method of quantification may be a useful adjunct to the visual assessment of single photon emission tomograms.     

Benefits of perfusion MR imaging relative to diffusion MR imaging in the diagnosis and treatment of hyperacute stroke

BACKGROUND AND PURPOSE: The development of thrombolytic agents for use with compromised cerebral blood flow has made it critical to quickly identify those patients to best treat. We hypothesized that combined diffusion and perfusion MR imaging adds vital diagnostic value for patients for whom the greatest potential benefits exist and far exceeds the diagnostic value of diffusion MR imaging alone. METHODS: The cases of patients with neurologic symptoms of acute ischemic stroke who underwent ultra-fast emergent MR imaging within 6 hours were reviewed. In all cases, automatic processing yielded isotropic diffusion images and perfusion time-to-peak maps. Images with large vessel distribution ischemia and with mismatched perfusion abnormalities were correlated with patient records. All follow-up images were reviewed and compared with outcomes resulting from hyperacute therapies. RESULTS: For 16 (26%) of 62 patients, hypoperfusion was the best MR imaging evidence of disease distribution, and for 15 of the 16, hypoperfusion (not abnormal diffusion) comprised the only imaging evidence for disease involving large vessels. For seven patients, diffusion imaging findings were entirely normal, and for nine, diffusion imaging delineated abnormal signal in either small vessel distributions or in a notably smaller cortical branch in one case. In all cases, perfusion maps were predictive of eventual lesions, as confirmed by angiography, CT, or subsequent MR imaging. CONCLUSION: If only diffusion MR imaging is used in assessing patients with hyperacute stroke, nearly one quarter of the cases may be incorrectly categorized with respect to the distribution of ischemic at-risk tissue. Addition of perfusion information further enables better categorizing of vascular distribution to allow the best selection among therapeutic options and to improve patient outcomes.     

Semi-automatic quantification of regional cerebral perfusion in primary degenerative dementia using 99m technetium-hexamethylpropylene amine oxime and single photon emission tomography

A new semi-automatic method for quantifying regional cerebral uptake of 99m technetium-hexamethylpropylene amine oxime (^99mTc-HMPAO) was used to assess single photon emission tomograms from 5 normal subjects, 14 patients with Alzheimer's disease, 14 patients with dementia of frontal lobe type and 4 patients with dementia with motor neurone disease. Uptake in both posterior cortical regions, although not in other regions, was significantly lower (P < 0.05) in Alzheimer's disease than in normal controls. Conversely in both dementia of frontal lobe type and dementia with motor neurone disease, uptake was significantly reduced (P < 0.05) compared with controls in all anterior cortical regions but not in posterior regions. Numerical findings in each disease mirrored the pattern of reduced tracer uptake previously reported by visual assessment. Nine patients were re-examined after an interval of at least 1 year. Comparison of follow-up scans with original images showed significant decreases in mid-anterior, left anterior and left posterior cortical uptake (P < 0.01) in patients with Alzheimer's disease and in left middle, left posterior and right posterior cortical uptake (P < 0.01) in patients with dementia of frontal lobe type. The method of quantification may be a useful adjunct to the visual assessment of single photon emission tomograms.     

基于fMRI的脑网络节点灵活度在血管性认知障碍患者中的研究

目的运用图论分析方法研究(vascular congnifive impairment,VCI)患者与正常者之间的脑网络节点灵活度差异,并将脑网络节点灵活度与临床认知评分进行相关性分析,探讨VCI患者认知功能改变的神经机制。方法纳入28例VCI患者作为病例组,纳入30例认知功能正常者作为对照组。两组均构建静息态脑网络,采用两独立样本t检验对比两组脑网络节点灵活度的差异。在控制性别、年龄、受教育程度的情况下,采用Pearson偏相关分析对VCI组的脑网络节点灵活度与MoCA评分作相关性分析。结果与对照组相比,VCI组在右侧顶内沟、左侧后扣带回、左侧颞叶、左小脑下部的节点灵活度显著降低,右侧枕叶节点灵活度显著升高,P值均<0.05。在控制性别、年龄、受教育程度等情况下,VCI组在右背外侧前额叶皮层及右枕叶后部的节点灵活度(r=-0.399,P=0.035)、(r=-0.387,P=0.042)与MoCA评分呈负相关;在左侧顶内沟区节点灵活度(r=0.393,P=0.039)与MoCA评分存在呈正相关。结论脑网络节点灵活度可以在一定程度上作为反映VCI的影像学标志,为VCI的早期诊断、病程监测、动态观察及预后评估提供依据。     

Tissue segmentation of the brain in Alzheimer disease.

PURPOSETo compare brain tissue in patients with Alzheimer disease with that in elderly control subjects by using high-resolution MR imaging and quantitative tissue-segmentation techniques.METHODSMR imaging of the brain was performed in 21 patients with Alzheimer disease and 17 control subjects. A computerized segmentation program was used to quantify volumes of ventricular and sulcal cerebrospinal fluid (CSF), white matter, cortical gray matter, and white matter signal hyperintensity. Statistical analysis was performed using analysis of variance.RESULTSWe found a significant decrease in total brain tissue and cortical gray matter and an increase in the ventricular and sulcal CSF in Alzheimer patients compared with control subjects. There was no difference in the volume of white matter. More white matter signal hyperintensities were found in Alzheimer patients, and a significant interaction between age and group was noted. Neuropsychological test scores correlated significantly with sulcal CSF in patients with Alzheimer disease.CONCLUSIONSemiautomated segmentation of MR images of the brains of patients with Alzheimer disease reveals significant brain atrophy attributable to loss of cortical gray matter, which is compatible with the pathologic features of Alzheimer disease. There is also a significant increase in white matter signal hyperintensities. Tissue segmentation may increase our understanding of dementia but, as yet, when used alone, it does not play a role in the premorbid diagnosis of Alzheimer disease.     

The scintigraphic evaluation of Huntington's disease and other movement disorders using single photon emission computed tomography perfusion brain scans.

The increasing availability of single-photon emission computed tomography (SPECT) perfusion brain scans has led to the investigation of a variety of neuropsychiatric conditions including the movement disorders such as Huntington's and Parkinson's disease. In general, observers have noted that Huntington patients have bilaterally decreased uptake of technetium 99m HM-PAO and iodine 123 IMP in the basal ganglia regions involving the heads of the caudate nucleic and adjacent structure, which reflects decreased neuronal function. These functional changes precede the morphological changes due to caudate nucleus atrophy that are observed on computed tomography and magnetic resonance imaging. Cortical changes occur in severely diseased Huntington's patients but are more nonspecific. Prediction of individuals at risk for Huntington's disease using SPECT scans should be done with caution and in association with other clinical data. In contrast, in Parkinson's disease mild diffusely decreased perfusion is commonly noted throughout the cerebral structures, except for the cerebellum. In Parkinson's disease, there is less agreement among observers as to whether the basal ganglia are abnormal. Some observers report that there are no specific basal ganglia perfusion defects in excess of those changes seen elsewhere in the brain. Others report diminished basal ganglia uptake associated with L-dopa therapy in some Parkinson's patients, and in patients with hemi-parkinsonism there have been perfusion deficits reported in the contralateral basal ganglia. In some Parkinson patients, bilateral Alzheimer's-like posterior temporoparietal cortical perfusion defects have been observed in association with progressive dementia. Basal ganglia and cortical perfusion changes also have been reported in a few patients with a variety of other less common movement disorders.     

Tc-99m HMPAO to demonstrate diffuse cortical necrosis in vivo

Tc-99m hexamethylpropylene amineoxime (HMPAO) is a novel radiopharmaceutical demonstrated to be a sensitive indicator of abnormalities of cerebral perfusion. Most reports in the literature have evaluated patients with gross perfusion deficits, such as cerebrovascular accidents, and with dementia, where patterns of diffuse perfusion deficit were reported comparable with those seen in PET studies. We report a patient in whom there was the rapid onset of dementia, with the HMPAO images demonstrating diffuse loss of cortical perfusion in a nonfocal, and nonsegmental, fashion. Correlation with postmortem examination demonstrates good concordance between the diffuse nature of HMPAO loss, and diffuse cortical necrosis throughout both cerebral hemispheres. The technique was shown to be more sensitive than transmission CT scanning in demonstrating the extent of the deficit, and it correlated closely with the functional deficits noted in the patient.     

Dilatation of the Virchow-Robin space is a sensitive indicator of cerebral microvascular disease: study in elderly patients with dementia

BACKGROUND AND PURPOSE: Virchow-Robin spaces (VRSs) are CSF spaces that accompany blood vessels as they perforate the brain substance. Dilatation of VRS is associated with microangiopathy. Microvascular disease has a major etiologic and pathogenetic role in dementias. To our knowledge, no investigators have looked at the relationship between dilated VRS on MR imaging and cerebral microvascular disease. The aim of our study was to test the hypothesis that dilatation of VRS is associated with subcortical vascular dementia. METHODS: We recruited 75 patients with Alzheimer's disease (n = 35), ischemic vascular dementia (n = 24), or frontotemporal dementia (n = 16) and 35 healthy volunteers. We assessed deep white matter and periventricular hyperintensities and the severity of VRS dilatation, as scored on MR images. Statistical group comparisons and multiple regression analyses were performed to quantify the relationship between imaging features and diagnoses. RESULTS: White matter lesions were more common in patients with ischemic vascular dementia than in those with Alzheimer's disease or healthy volunteers (P < .01). VRS scores were significantly higher in patients with vascular dementia than in patients with AD (P < .001), patients with FTD (P < .01), or healthy volunteers (P < .001). VRS scores accounted for 29% of the variance in the regression model, and scores for periventricular hyperintensity accounted for 2%. CONCLUSION: VRS dilatation is common in diseases associated with microvascular abnormality and can be used as a diagnostic tool to differentiate vascular dementias from degenerative dementias.     

Paget disease: MR imaging findings

Magnetic resonance (MR) images of 13 patients with Paget disease were reviewed, and findings were correlated with those from computed tomographic (CT) scans, radiographs, and, in two patients, surgical biopsy. MR imaging findings correlated with CT and radiographic findings of cortical thickening, increased size of bone, and coarse thickened trabeculae. Focal or diffuse decreased signal intensity, representing dense bone, was seen on images obtained with short and long repetition times (TRs) and echo times (TEs); high-signal foci, representing fat collections, were seen on short TR/TE images; and high-signal foci, representing fibrovascular marrow in active Paget disease, were seen on long TR/TE images. Complications of Paget disease-including basilar invagination, spinal stenosis, and sarcoma--were well identified on MR images. Although MR imaging is not generally used in diagnosis of Paget disease, the disease will be encountered more frequently as more MR imaging examinations are performed. An awareness of the range of findings in Paget disease is useful in evaluating MR images of the musculoskeletal and other systems.