Differential lesion patterns in CADASIL and sporadic subcortical arteriosclerotic encephalopathy: MR imaging study with statistical parametric group comparison

PURPOSE: To differentiate lesion patterns in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) from those in patients with sporadic subcortical arteriosclerotic encephalopathy (sSAE). MATERIALS AND METHODS: Magnetic resonance (MR; T2-weighted and fluid-attenuated inversion-recovery) images obtained in 28 patients with CADASIL were compared with images obtained in 24 patients with sSAE by using an automated pixel-based group comparison with statistical parametric mapping and regional semiquantitative rating. RESULTS: Visual rating showed higher lesion scores for CADASIL in the temporal and temporopolar white matter (WM). Statistical parametric mapping group analysis independently revealed more extensive bilateral involvement of the anterior temporal and superior frontal WM in CADASIL. There were bilateral signal intensity reductions within the dentate nucleus, deep cerebellar WM, crus cerebri, and thalamus. Lesions extended remarkably more often into arcuate fibers in the temporopolar and paramedian superior frontal lobes in CADASIL. Linear discriminant analysis was used to classify 96% (50 of 52) of the cases correctly, with temporopolar WM and arcuate fiber involvement contributing most to the discrimination function. CONCLUSION: The presented MR imaging criteria are useful in the diagnostic work-up in patients with leukoencephalopathy and help to differentiate CADASIL from sSAE. The observed pattern of vulnerability in CADASIL suggests future directions for research in the pathophysiology of this disorder. In addition, the study demonstrates the potential of automated image analysis to explore MR imaging lesion patterns.     

2个CADASIL患者的弥散张量成像与20例正常人的比较

目的　分析2例CADASIL患者的MR特点及弥散张量指标的变化。方法　收集2例通过病理和基因检查确诊为CA DASIL的先证者的临床资料,对其进行常规MR扫描和弥散张量成像,将弥散张量成像的指标与20例正常志愿者的指标进行比较。结果　2例CADASIL患者的MR主要表现为双侧额顶叶白质内多发腔梗、脱髓鞘改变和双侧颞叶前部白质脱髓鞘。1例患者双侧外囊、内囊后肢、胼胝体膝部和压部的部分各向异性(FA)值均小于正常组的平均值减去2倍标准差,另1例患者左侧外囊的FA值小于对照组的平均值减去2倍标准差。结论　常规MR表现和弥散张量成像指标的测量均反映了CADASIL患者中存在严重的白质病变。     

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: structural MR imaging changes and apolipoprotein E genotype

BACKGROUND AND PURPOSE: Apolipoprotein E (apoE) genotype plays an important role in the development, maintenance, and response to injury of the central nervous system. It has been suggested that apoE epsilon4 genotype is a risk factor for several neurologic disorders. We investigated the correlation between the apoE genotype and radiologic data in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). METHODS: T1-weighted, dual fast spin-echo, T2*-weighted gradient echo, and fluid-attenuated inversion recovery MR imaging scans were obtained from 36 CADASIL patients (21-59 years of age). The number of lacunar infarcts and microbleeds and the presence of subcortical lacunar lesions were determined. The amount of white matter hyperintensities was assessed by using semiautomated segmentation software. The relation between the radiologic endophenotype of CADASIL and the apoE genotype was assessed by using a Student t test for unpaired data and Fisher exact test. RESULTS: White matter hyperintensities, lacunar infarcts, microbleeds, and subcortical lacunar lesions were not found to be associated with the presence of an epsilon4 allele. CONCLUSION: The variability of structural MR imaging lesions in CADASIL is independent of apoE genotype and other processes must underlie the variable natural history of the disease.     

Cortical hypometabolism and crossed cerebellar diaschisis suggest subcortically induced disconnection in CADASIL: an 18F-FDG PET study.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited small-vessel disease caused by mutations in the NOTCH3 gene. As in sporadic small-vessel disease, ischemic lesions are largely confined to subcortical structures, whereas the cortex is spared. CADASIL, therefore, may serve as a model to study subcortically induced remote effects. The purpose of this study was to evaluate with (18)F-FDG PET whether regional cerebral metabolic rate of glucose (rCMRglc) is altered in CADASIL patients and, if so, whether there is evidence of subcortically induced disconnection. METHODS: Eleven CADASIL patients (7 women, 4 men; mean age, 55.8 +/- 6.7 y) without cortical lesions on brain MR images underwent PET after intravenous injection of 120 MBq (18)F-FDG, with calculation of rCMRglc according to a previously published method. For further processing, patient studies were registered to a template of a healthy control group and region-of-interest-based and voxelwise comparisons were performed. RESULTS: In CADASIL patients, mean rCMRglc was significantly reduced in all cortical and subcortical structures, compared with the values in healthy volunteers. In the subcortical gray matter, metabolic rates, given as the percentage of the mean of healthy volunteers, were 49.7%, 65.3%, and 51.6% in the caudate, putamen, and thalamus, respectively. Among cortical structures, the values were 66.9%, 67.9%, 67.2%, and 76.5% for the frontal, parietal, temporal, and occipital lobes, respectively. On an individual level, most patients showed marked asymmetry and inhomogeneities of cortical glucose metabolism. In 6 (55%) CADASIL patients, there was evidence of crossed cerebellar diaschisis. CONCLUSION: This study showed that cortical glucose metabolism is significantly lower in CADASIL patients than in healthy volunteers. The observed decrease in rCMRglc may in part be explained by a reduction of cerebral blood flow and neuronal loss. In addition, our data provide evidence of remote effects secondary to the functional disruption of subcortical fiber tracts in this particular type of small-vessel disease.     

Cerebral cortical and white matter lesions in amyotrophic lateral sclerosis with dementia: correlation with MR and pathologic examinations

BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis with dementia (ALSD) is a progressive neurodegenerative disorder, characterized clinically by motor neuron symptoms and dementia, and pathologically by degeneration of the motor neurons of the brain and spinal cord as well as atrophy of the frontal and/or temporal lobes. So far, there has been no study on the correlation of MR images with histologic findings in ALSD. We studied the correlation of antemortem and postmortem T2-weighted MR images with histologic findings in autopsy-proved cases of ALSD. MATERIALS AND METHODS: Antemortem and postmortem T2-weighted images were compared with histologic findings in 3 autopsy-proved cases of ALSD. RESULTS: Antemortem MR images showed atrophy of the frontal and temporal lobes, which were asymmetric in the medial-ventral part of the temporal lobe. Faint linear T2-hyperintensity was seen in the medial-ventral part of the temporal subcortical white matter in 1 case. Postmortem T2-weighted images showed linear subcortical hyperintensity in the ventral-medial temporal lobe in each case. Histologically, cortical atrophy on MR images showed spongiform change with neuronal loss and gliosis especially in the superficial layers and linear subcortical hyperintensity on T2-weighted images showed degeneration and gliosis in each case. These findings are characteristic histologic changes of ALSD. CONCLUSION: MR imaging of atrophy of the frontal and temporal lobes with linear subcortical hyperintensities in the anteromedial temporal lobe is useful for diagnosis of ALSD.     

常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病患者的MR定量指标及其与临床的关系

目的 对常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病(CADASIL)患者的白质高信号和脑体积进行定量分析,并探讨其与临床的关系.方法 15例通过病理检查确诊为CADASIL的患者进行常规MR扫描,统计脑半卵圆中心、内囊后肢、外囊、胼胝体和颞极白质受病变累及情况.利用计算机后处理软件计算标准化颅脑体积和白质高信号占颅脑体积的百分比,并与年龄、美国国立卫生研究院卒中量表(NIHSS)和简易精神状态检查(MMSE)量表评分进行Spearman相关性分析.结果 CADASIL患者的白质病变累及部位依次为:半卵圆中心(13/15)、颞极白质(10/15)、外囊(8/15)、内囊后肢(5/15)、胼胝体(4/15).白质高信号占颅脑体积的百分比为(5.7±1.4)%,标准化颅脑体积为(1602±58)×103mm3.年龄与标准化颅脑体积呈负相关(r=-0.555,P＜0.05);白质高信号百分比与NIHSS、MMSE量表评分分别呈正、负相关(r=0.522,P＜0.05;r=-0.679,P＜0.01);标准化颅脑体积与NIHSS评分呈负相关(r=-0.624,P＜0.05).结论 CADASIL患者的白质高信号和脑体积可以定量测量,这两种影像学指标可以在一定程度上反映患者的病情.白质高信号的发展可能预示患者认知功能的下降.     

The spatial distribution of MR imaging abnormalities in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy and their relationship to age and clinical features

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a condition causing recurrent subcortical strokes. MR imaging, which shows focal lacunar infarcts and leukoaraiosis, plays a central role in the diagnosis and evaluation. We studied MR imaging abnormalities in a large prospectively recruited cohort of CADASIL patients to describe the spatial distribution of abnormalities, determine how this distribution alters with age, and identify any correlations with the clinical features of the disease. METHODS: In this study, 112 CADASIL subjects from 64 families were prospectively recruited. MR imaging scans were graded by a single neuroradiologist, by using the modified Scheltens scale, to quantify the severity of high-signal-intensity changes in different brain regions. RESULTS: Lesion load increased progressively with age. Scores were maximal in the frontal, parietal, and anterior temporal cortex, and the external capsule; intermediate in the pons; and relatively low in the corpus callosum, caudate, globus pallidus, cerebellum, midbrain, and medulla. Anterior temporal pole involvement was common at all ages and, when present, usually confluent, but this was absent in 33% of patients 20-29 years of age. A history of stroke correlated with total Scheltens score and internal capsule and pontine scores. Dementia correlated with total Scheltens score and subcortical white matter score, whereas depression correlated with subcortical white matter score but not total Scheltens score. CONCLUSIONS: There is a characteristic pattern of MR imaging abnormalities in CADASIL that aids in differential diagnosis; however, some characteristic features, such as anterior temporal pole involvement, can be absent. MR imaging lesion load correlated with some clinical features including stroke and dementia, whereas depression is more common in individuals with deep white matter changes.     

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: decrease in regional cerebral blood volume in hyperintense subcortical lesions inversely correlates with disability and cognitive performance

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathic syndrome related to a genetic defect on chromosome 19. Characteristic changes in CADASIL can be observed onT2-weighted MR images in the subcortical white matter. The purpose of this study was to measure changes of regional cerebral blood volume (rCBV) with dynamic contrast-enhanced MR imaging and to correlate the changes to disability and cognitive performance. METHODS: We obtained rCBV measurements of 24 individuals with proven CADASIL on a 1.5-T MR imaging unit. A susceptibility-weighted MR imaging sequence was used for bolus tracking. Principles of the indicator dilution theory were applied to estimate values of absolute rCBV (mL/100 g). Disability was determined by using the Rankin scale, and overall cognitive performance was assessed by using the Mini-Mental State Examination. RESULTS: The mean rCBV in the subcortical white matter that was hyperintense on the T2-weighted images (2.7 +/- 0.8 mL/100 g) was significantly lower than the rCBV in the white matter that appeared normal on the T2-weighted images (4.4 +/- 1.3 mL/100 g) (P <.05). The mean rCBV in the gray matter was within the normal range (8.3 +/- 1.7 mL/100 g). Both cognitive impairment and disability negatively correlated with rCBV in the subcortical white matter that was hyperintense (P <.05) but not with rCBV in the normal appearing white matter. rCBV did not correlate with age. CONCLUSION: rCBV measured in the hyperintense subcortical white matter in individuals with CADASIL was decreased and inversely correlated with disability and cognitive impairment.     

常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病的颅脑MRI表现

目的 提高对常染色体显性遗传性脑动脉病伴皮层下梗死和白质脑病(CADASIL)的颅脑MRI表现的认识.方法 对一家系2代5例患者进行头颅常规MR和MR血管成像(MRA)检查.对经Notch3基因检查或皮肤组织活检超微病理检查确诊的3例和经MRI与临床诊断的1例CADASIL的MRI资料进行分析.结果 MR检查的5例中4例CADASIL均获得明确诊断,1例排除诊断.4例CADASIL均见两侧颞叶、额叶和顶叶大致对称性皮层下与侧脑室旁白质病灶,呈长T1、长T2信号,但枕叶累及甚少且皮层不受累;O'Sullivan征阳性4例,皮层下腔隙性损害(SLLs)征阳性2例;3例半卵圆中心可见多发圆形或卵圆形囊性梗死即"黑洞",4例均见多发圆点状血管周间隙即"胡椒罐盖"样征象;4例全部显示胼胝体单发或多发斑片状显著长T1、长T2信号,其中2例伴萎缩;内囊前肢与外囊均受累,呈"人"字征;基底节和脑干可见单发或多发陈旧性腔隙性梗死灶;1例伴右侧小脑小片状梗死灶;4例全部有轻度至中度的脑干、小脑和大脑萎缩;MRA颅内Ⅰ-Ⅲ级较大动脉均未见明显异常.结论 CADASIL的颅脑MRI表现具有一定的特征性,可为CADASIL的初诊和筛选提供重要依据.     

Symmetric temporal abnormalities on MR imaging in amyotrophic lateral sclerosis with dementia

BACKGROUND AND PURPOSE: Our aim was to clarify imaging findings of amyotrophic lateral sclerosis with dementia (ALSD). MATERIALS AND METHODS: T2-weighted MR images (T2WI) of 3 patients with ALSD (2 men, 1 woman; 58-71 years of age) and 21 patients with ALS without dementia (12 men, 9 women; 46-74 years of age) were examined for frontotemporal lobar atrophy and signal-intensity alterations in the white matter of the anterior temporal lobes, corticospinal tracts (CST), and precentral gyri and in precentral cortices. The brain of one of the patients with ALSD was examined at autopsy. RESULTS: All patients with ALSD showed bilateral frontotemporal atrophy mostly with temporal lobe dominance. In the ALSD group, T2WI demonstrated hyperintensity in the subcortical white matter on the medial side of the anterior temporal lobes, whereas in the group without dementia, none showed this imaging finding. MR images demonstrated no abnormal signal-intensity changes in CST in the internal capsule or the brain stem in the ALSD group. In the group without dementia, 6 patients (28.6%) showed this imaging finding. In neuropathologic examinations of the brain of 1 patient with ALSD, myelin-stained sections of the brain demonstrated loss of myelin in the subcortical white matter on the medial side of the anterior temporal white matter. CONCLUSIONS: A symmetric pattern of frontotemporal atrophy and anteromedial subcortical hyperintensities in the temporal lobes on T2WI could be characteristic of ALSD.     

Late radiation injury to the temporal lobes: morphologic evaluation at MR imaging

PURPOSE: To study the morphologic characteristics of late radiation injury to the temporal lobes of the brain on magnetic resonance (MR) images. MATERIALS AND METHODS: This was a prospective study involving 34 patients (age range, 37-72 years) with known radiation injury to the temporal lobes from radiation therapy administered 2-10 years previously for nasopharyngeal carcinoma MR imaging was performed with T2-weighted gradient- and spin-echo, gradient-recalled echo, T1-weighted spin-echo, fluid-attenuated inversion-recovery, and T1-weighted postcontrast spin-echo sequences. RESULTS: Radiation injury was present in 57 of the 68 temporal lobes. The white matter lesions in radiation-induced injury were predominantly hyperintense on T2-weighted images, but in 37 (65%) of the 57 lobes, foci with heterogeneous signal intensity consistent with necrosis were detected. In the 57 involved lobes, gray matter lesions were detected in 50 (88%); blood-brain barrier disruption based on parenchymal contrast enhancement, in 51 (89%); and hemosiderin deposits, in 30 (53%). There was a significant correlation between white matter necrosis, gray matter lesions, and blood-brain barrier disruption, all of which were located mainly in the inferior temporal lobes that received the highest radiation dose. CONCLUSION: The lesion components of radiation-induced injury to the temporal lobes at MR imaging were more varied than have been previously described. In addition to the classic white matter lesions, gray matter lesions, blood-brain barrier disruption, and hemosiderin deposition also were frequently seen.     

Computer-aided evaluation method of white matter hyperintensities related to subcortical vascular dementia based on magnetic resonance imaging

It has been reported that the severity of subcortical vascular dementia (VaD) correlated with an area ratio of white matter hyperintensity (WMH) regions to the brain parenchyma (WMH area ratio). The purpose of this study was to develop a computer-aided evaluation method of WMH regions for diagnosis of subcortical VaD based on magnetic resonance (MR) images. A brain parenchymal region was segmented based on the histogram analysis of a T1-weigthed image. The WMH regions were segmented on the subtraction image between a T1-weighted and fluid-attenuated inversion-recovery (FLAIR) images using two segmentation methods, i.e., a region-growing technique and a level-set method, which were automatically and adaptively selected on each WMH region based on its image features by using a support vector machine. We applied the proposed method to 33 slices of the three types of MR images with 245 lesions, which were acquired from 10 patients (age range: 64–90 years, mean: 78) with a diagnosis of VaD on a 1.5-T MR imaging scanner. The average similarity index between regions determined by a manual method and the proposed method was 93.5 ± 2.0% for brain parenchymal regions and 78.2 ± 11.0% for WMH regions. The WMH area ratio obtained by the proposed method correlated with that determined by two neuroradiologists with a correlation coefficient of 0.992. The results presented in this study suggest that the proposed method could assist neuroradiologists in the evaluation of WMH regions related to the subcortical VaD.     

Increased subcortical patellar signal intensity at T2-weighted MR imaging: a subacute finding after knee injury

PURPOSE: To investigate the temporal prevalence of a rim of increased signal intensity in the subcortical part of the patella at T2-weighted magnetic resonance (MR) imaging after arthroscopic knee surgery or knee injury. MATERIALS AND METHODS: The prospective and retrospective components of the study were performed after receiving approval from the institutional research ethics board. Written informed consent was obtained for the prospective component of the study. The need for informed consent was waived for the retrospective component of the study. The authors performed a prospective evaluation of serial MR images of the knee of four patients (three men and one woman; age range, 28-53 years; mean age, 36.8 years) after arthroscopic anterior cruciate ligament (ACL) reconstruction. They also performed a retrospective review of MR images of the knee from 90 consecutive patients (59 male and 31 female patients; age range, 13-66 years; mean age, 34.6 years) referred for the evaluation of an ACL injury. All imaging studies were evaluated in consensus by two musculoskeletal radiologists for the presence of a rim of increased signal intensity in the subcortical part of the patella at T2-weighted imaging. The presence of this signal intensity pattern was correlated with the time to imaging from surgery or joint injury. Logistic regression modeling was performed with increased subcortical signal intensity as the outcome and a second-degree polynomial for elapsed time as the predictor. RESULTS: All four patients who underwent imaging prospectively after ACL surgery showed increased T2-weighted signal intensity in the subcortical part of the patella 12 weeks after surgery. None of the patients showed these signal intensity changes at 6 or 24 weeks. A subcortical rim of increased T2-weighted signal intensity was seen in the patella in 24 (27%) of the 90 consecutive patients who underwent imaging for the assessment of possible ACL injury. Significant independent differences were seen in the prevalence of increased T2-weighted signal intensity in the subcortical part of the patella when related to time between injury and MR imaging (P = .002), with an increase in prevalence as time since injury increased and a decrease in prevalence in patients who underwent MR imaging more than 20 weeks after injury (P = .013). CONCLUSION: Increased T2-weighted signal intensity in the subcortical part of the patella appears to be a subacute transient MR finding seen after knee surgery or injury.     

Cerebral blood flow by using pulsed arterial spin-labeling in elderly subjects with white matter hyperintensities

BACKGROUND AND PURPOSE: On MR imaging, white matter hyperintensities (WMH) on T2-weighted images are generally considered as a surrogate marker of ischemic small vessel disease in elderly subjects. Pulsed arterial spin-labeling (PASL) is a noninvasive MR perfusion-weighted technique. We hypothesized that elderly subjects with diffuse confluent WMH should have lower cerebral blood flow (CBF) measurements than subjects with punctiform or beginning confluent WMH.MATERIALS AND METHODS: MR images of 21 subjects (13 women; mean age, 76 years; SD, 5), stratified for the degree of WMH, from a single center within the multinational Leukoaraiosis and Disability (LADIS) study, were investigated. CBF images were obtained by means of quantitative imaging of perfusion by using a single-subtraction second version, with thin-section TI periodic saturation PASL. Values of cortical gray matter, subcortical (including white matter and deep gray matter), and global CBF were calculated. CBF measurements of subjects with diffuse confluent WMH (n = 7) were compared with those of subjects with punctiform or beginning confluent WMH (n = 14).RESULTS: Subjects with diffuse confluent WMH were found to have approximately 20% lower mean global CBF (43.5 mL/100 mL/min; SD, 6.3) than subjects with punctiform or beginning confluent WMH (57.9 mL/100 mL/min; SD, 8.6; P < .01), as well as approximately 20% lower mean subcortical (P < .01) and cortical gray matter CBF (P < .05).CONCLUSION: PASL revealed a significant reduction of CBF measurements in elderly subjects with diffuse confluent WMH.

On MR imaging, white matter hyperintensities (WMH) on T2-weighted images, fluid-attenuated inversion recovery (FLAIR) images, and proton density–weighted images are generally considered as a surrogate marker of ischemic small vessel disease in elderly subjects,¹ but their significance is still under debate.Arterial spin-labeling (ASL) is a functional MR imaging technique that represents an alternative to both nuclear medicine and dynamic susceptibility contrast echo-planar MR imaging (EPI) for the evaluation of cerebral perfusion. By using water as a diffusible tracer, ASL does not require either ionizing radiation or an exogenous contrast bolus injection. Water proton spins in the arterial blood can be inverted (magnetically labeled) before entering the capillary level, after applying an appropriate series of radio-frequency pulses. When these labeled water protons enter the capillary level, they alter the magnetization of the tissue in a way that can be measured quantitatively.² Pulsed ASL (PASL) techniques generally label a large blood volume in a thick slab just below the planes of image acquisition, by inverting the magnetization of water protons with adiabatic hyperbolic secant radio-frequency pulses.³Because WMH most probably represent ischemic small vessel disease,^1,4 we hypothesized that subjects with diffuse confluent WMH should have lower cerebral blood flow (CBF) measurements than subjects with punctiform or beginning confluent WMH. In fact, single-photon emission CT, positron-emission tomography, and dynamic susceptibility contrast perfusion-weighted MR imaging studies have shown that diffuse confluent WMH are associated with reduced cerebral perfusion,^5–7 but most of them did not yield quantification of CBF. To our knowledge, no previous study has shown a relation between different grades of WMH and CBF measurements by means of ASL. Therefore, our purpose was to compare CBF measurements of subjects with diffuse confluent WMH with those of subjects with punctiform or beginning confluent WMH by using PASL.     

MR imaging of head trauma: review of the distribution and radiopathologic features of traumatic lesions

The distribution and extent of traumatic lesions were prospectively evaluated with MR imaging in 40 patients with closed head injuries. Primary intraaxial lesions were classified according to their distinctive topographical distribution within the brain and were of four main types: (1) diffuse axonal injury (48.2%), (2) cortical contusion (43.7%), (3) subcortical gray-matter injury (4.5%), and (4) primary brainstem injury (3.6%). Diffuse axonal injury most commonly involved the white matter of the frontal and temporal lobes, the body and splenium of the corpus callosum, and the corona radiata. Cortical contusions most frequently involved the inferior, lateral, and anterior aspects of the frontal and temporal lobes. Primary brainstem lesions were most commonly seen in the dorsolateral aspects of the rostral brainstem. The pattern and distribution of primary lesions seen by MR were compared with those expected from previous pathologic studies and found to be quite similar. Our data and review of the literature would also indicate that MR detects a more complete spectrum of traumatic lesions than does CT. Secondary forms of injury (territorial arterial infarction, pressure necrosis from increased intracranial pressure, cerebral herniation, secondary brainstem injury) were also visible by MR in some cases. The level of consciousness was most impaired in patients with primary brainstem injury, followed by those with widespread diffuse axonal injury and subcortical gray-matter injury. The best MR imaging planes, pulse sequences, and imaging strategies for evaluating and classifying traumatic lesions were evaluated, and the mechanisms by which traumatic stresses result in injury were reviewed. MR was found to be superior to CT and to be very effective in the detection of traumatic head lesions and some secondary forms of injury. While T2-weighted images were most useful for lesion detection, T1-weighted images proved to be most useful for anatomic localization and classification.     

Combinations of the presence or absence of cerebral microbleeds and advanced white matter hyperintensity as predictors of subsequent stroke types

BACKGROUND AND PURPOSE: Previous studies have shown microbleeds to be a risk factor for intracerebral hemorrhage and white matter hyperintensity (WMH) to be a risk factor for ischemic stroke. This study was performed to determine whether combinations of the presence or absence of microbleeds and advanced WMH are risk factors for subsequent recurrent stroke types. METHODS: In 266 patients with stroke, microbleeds on T2*-weighted MR images were counted, and WMH on T2-weighted images was graded. Patients were divided into 4 groups by the combinations of the presence or absence of microbleeds and advanced WMH and were followed up for stroke recurrence. RESULTS: During a mean follow-up period of 564.8 +/- 220.5 days, 26 patients developed recurrent strokes, including 10 intracerebral hemorrhages and 16 ischemic strokes. Patients with microbleeds without advanced WMH (n = 42) developed only intracerebral hemorrhages (n = 8), and the recurrence rate of intracerebral hemorrhage in those patients estimated by the Kaplan-Meier method was the highest in the 4 groups (14.3% in 1 year and 21.2% in 2 years). In contrast, patients with advanced WMH without microbleeds (n = 39) developed only ischemic strokes (n = 6), and the estimated recurrent rate of ischemic stroke in those patients was the highest in the 4 groups (10.5% in 1 year and 17.4% in 2 years). Cox proportional hazards regression analysis revealed that microbleeds were associated with intracerebral hemorrhage (hazard ratio [HR], 85.626; 95% confidence interval [CI], 6.344-1155.649) and that advanced WMH was negatively associated with intracerebral hemorrhage (HR, 0.016; 95% CI, 0.001-0.258). Advanced WMH was associated with ischemic stroke (HR, 10.659; 95% CI, 2.601-43.678). CONCLUSION: It appears that patients at high risk of subsequent intracerebral hemorrhage or ischemic stroke can be identified by combinations of the presence or absence of microbleeds and advanced WMH.     

Terminal zones of myelination: MR evaluation of children aged 20-40 months

BACKGROUND AND PURPOSE: MR imaging is the method of choice for assessment in vivo of the development of myelination of the human central nervous system. During the first months of life, the myelination process follows well-defined steps, whereas little information exists about the later phases of myelination. To improve our understanding of this aspect and to identify the specific sites involved in the process of myelination in its terminal phase, we evaluated normal MR brain studies in children aged 20-40 months. METHODS: We retrospectively evaluated 85 MR brain studies of 81 children aged 20-40 months who were without diseases potentially affecting white matter. The MR studies were performed with a 1.5-T system, with T2-weighted spin-echo and turbo spin-echo sequences. Subjective analysis of the signal intensity of the white matter was made in four areas: subcortical frontal, temporal, and parietal lobes and peritrigonal region. Extension of myelination was graded on an ordinal scale; 0 indicated the absence of myelin, and the maximum value indicated complete myelination. RESULTS: A persistent T2 hyperintensity of the subcortical areas was noted after 20 months of age. With advancing age, a progressive increase in the grade of myelination was noted in these regions, and at about 40 months of age myelination was complete. However, in most of our patients aged 20 months, myelination in the peritrigonal areas appeared complete. CONCLUSION: The only area that can still exhibit a persistent T2 hyperintensity on MR images at about 2 years of age is considered to be the peritrigonal region: the so-called terminal zone. At this age in our patients, however, a persistent T2 hyperintensity was noted in the frontotemporal subcortical regions. In these areas, the myelination appeared complete at 36-40 months of age. The so-called terminal zones were the subcortical areas rather than the peritrigonal area, and complete myelination took place by about age 3 years.     

Distribution of cranial MRI abnormalities in patients with symptomatic and subclinical CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare, inherited cause of early stroke and dementia, with a poor prognosis. This study was performed to clarify lesion appearance and pattern of lesion distribution in CADASIL. 20 members of a single family were tested for the CADASIL gene mutation and studied with cranial MRI. Scans were evaluated for lesion load and pattern of lesion distribution. 19 patients had cranial MRI, of whom 11 had normal MRI scans, were clinically unaffected and tested negative for the CADASIL gene mutation. The remaining eight patients had abnormal cranial MRI scans: seven patients were positive for the CADASIL gene mutation and one (untested) patient was severely clinically affected. Three of the patients who tested positive for the CADASIL gene mutation were clinically unaffected at the time of imaging. All eight patients with abnormal cranial MRI had subcortical white matter abnormalities, mostly in frontal and temporal lobes. Lesions involving the corpus callosum were present on sagittal T2 weighted images in four of five clinically affected and one of three clinically unaffected patients. Lesions involving the deep grey nuclei and the brain stem were common. On T1 weighted images, lesions were either poorly defined (confluent white matter hypointensity) or well defined (cystic infarcts or enlarged perivascular spaces). Atrophy was infrequent. Familiarity with the range of cranial MRI appearances may aid diagnosis of CADASIL. Recognition of cranial imaging features in asymptomatic CADASIL patients could prompt earlier diagnosis.     

Frequency of subclinical lacunar infarcts in ischemic leukoaraiosis and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

BACKGROUND AND PURPOSE: Small vessel cerebrovascular disease is an important cause of vascular cognitive impairment. It is usually sporadic but also occurs secondary to the genetic disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Recurrent lacunar stroke is a characteristic feature, although symptomatic events are relatively rare, making large numbers necessary for evaluation of potential therapies. Diffusion-weighted imaging is sensitive to acute ischemic lesions and differentiates them from chronic infarcts. Detection of asymptomatic lacunar infarcts with diffusion-weighted imaging is a potential surrogate marker for treatment trials. In this study, the frequency of asymptomatic new lesions in ischemic leukoaraiosis and CADASIL was determined as a step toward assessing the potential of this technique as a surrogate marker of disease activity. METHODS: Fifty patients with sporadic small vessel disease and 19 patients with CADASIL underwent diffusion-weighted imaging. All had been asymptomatic for 3 months before imaging. Diffusion-weighted images were screened by two raters for new lesions; lesions were confirmed as recent by a visible reduction of diffusivity on the corresponding apparent diffusion coefficient maps. RESULTS: Recent ischemic lesions were identified in four patients with sporadic small vessel disease (8.0%) and two patients with CADASIL (10.5%). CONCLUSION: Asymptomatic new lesions are found in cases of sporadic small vessel disease and CADASIL. The frequency of new lesions suggests that this approach has a potential role as a surrogate marker in therapeutic trials that warrants further investigation.     

Subcortical low intensity on MR images of meningitis, viral encephalitis, and leptomeningeal metastasis

BACKGROUND AND PURPOSE: Subcortical low-intensity lesion on T2-weighted images is an uncommon manifestation of ischemia, multiple sclerosis, and Sturge-Weber disease. This study was performed to determine whether subcortical low signal intensity is an MR feature of meningitis, viral encephalitis, or leptomeningeal metastasis and to investigate a cause of subcortical low intensity. METHODS: We retrospectively reviewed MR images of 117 patients with meningitis, encephalitis (viral or unknown), or leptomeningeal metastasis for the presence of subcortical low intensity, meningeal enhancement, signal intensity change of cortex, and change in subcortical low intensity on follow-up images. Diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) maps were obtained in 55 patients. Subcortical low-intensity lesions were also quantitatively analyzed on T2-weighted, fluid-attenuated inversion recovery (FLAIR), and DW images. RESULTS: Subcortical low intensity was found in nine (23.7%) of 38 patients with encephalitis (viral, 31; unknown origin, 7), five (24%) of 21 with leptomeningeal metastasis, and five (9%) of 58 with meningitis. Leptomeningeal enhancement was observed in 100% and cortical hyperintensity in 14 (74%) of 19 patients with subcortical low intensity. Leptomeningeal enhancement was seen in 46 (47%) and cortical hyperintensity in 33 (34%) of 98 patients without subcortical low intensity. Subcortical low intensity disappeared or decreased in extent on follow-up MR images in all seven patients who underwent follow-up. ADC of subcortical low-intensity lesions was lower than that of the contralateral area and decreased by 9.3 +/- 11.4%. CONCLUSION: Subcortical low intensity was uncommonly found in meningitis, viral encephalitis, and leptomeningeal metastasis. It is a nonspecific MR sign of various meningeal and cortical diseases. Although the cause of subcortical low intensity remains uncertain, free radical formation may play a role as a causative factor.