Evolution of lesions in Susac syndrome at serial MR imaging with diffusion-weighted imaging and apparent diffusion coefficient values

BACKGROUND AND PURPOSE: Susac syndrome is a rare disorder consisting of encephalopathy, hearing loss, and retinal arteriolar occlusions. The purpose of this study was to evaluate the evolution of lesions in this disease by using serial MR imaging with diffusion-weighted imaging (DWI) and apparent diffusion coefficients (ADCs). Abnormalities in the nonlesional white matter (NLWM) were also analyzed. METHODS: Serial MR and DWI findings in two patients with Susac syndrome were reviewed retrospectively. ADCs of the lesions and the NLWM were compared with values of the corresponding anatomical regions in 16 control subjects. RESULTS: T2-weighted images, DWIs, and fluid-attenuated inversion-recovery (FLAIR) images demonstrated diffuse small hyperintense lesions predominantly involving the corpus callosum, white matter, cerebral cortex, and deep gray structures. During the whole course in the two patients, 437, 295, and 113 lesions were depicted on FLAIR images, T2-weighted images, and DWIs, respectively. With the aggravation and mitigation of the clinical symptoms, the size and number of the lesions changed over time. Of 65 lesions with measured ADCs, six had restricted ADCs (5.29-6.91 x 10(-4) mm(2)/s), and 29 had elevated ADCs (8.02-13.5 x 10(-4) mm(2)/s). With disease progression, ADCs in the NLWM changed from normal to elevated; this corresponded to the diffuse signal-intensity change seen in the white matter. CONCLUSION: FLAIR imaging is the most sensitive sequence for detecting lesions of Susac syndrome. DWI is useful in demonstrating the heterogeneous nature of lesions, depicting occult abnormalities in the white matter, elucidating underlying pathologic processes, and conducting patient follow-up.     

Creutzfeldt-Jakob disease: comparative analysis of MR imaging sequences

BACKGROUND AND PURPOSE: MR imaging has played an increasingly important role in the diagnosis of Creutzfeldt-Jakob disease (CJD) since basal ganglia abnormalities on T2-weighted images have been described; thus, the aim of our study was to compare the value of different MR images in the diagnosis of CJD. METHODS: One hundred fifty-seven patients with CJD underwent MR imaging examinations. Ninety-two patients were neuropathologically confirmed, and 65 were clinically classified as having CJD through the CJD Surveillance Unit (probability of 95%). There was no standardized MR imaging protocol; thus, the examinations included 143 T2-weighted, 43 proton attenuation (PD)-weighted, 84 fluid-attenuated inversion recovery (FLAIR), and 44 diffusion-weighted images (DWI). The MR images were reviewed for pathologic changes of the basal ganglia, thalamus, and cerebral cortex. RESULTS: Cortical abnormalities were present in 70 patients (45%) and were visible in 80% (35/44) of all available DWI examinations. The basal ganglia were affected in 94 patients (60%), in particular in the caudate nucleus; the most sensitive sequences were DWI (64%) and PD-weighted (63%). A thalamic involvement was more frequently diagnosed on PD-weighted images (19%) and DWI (14%) than on FLAIR or T2-weighted images. CONCLUSION: PD-weighted images and DWI showed better results in the diagnosis of signal intensity changes in the basal ganglia compared with T2-weighted or FLAIR images; however, in the diagnosis of cortical changes, DWI was clearly superior. Our data suggest that DWI is the most sensitive MR imaging technique in the diagnosis of CJD.     

MR扩散加权成像对Creutzfeldt-Jakob病的诊断意义

目的评价MR扩散加权像(DWI)对Creutzfeldt-Jakob病(CJD)的诊断价值。方法8例散发性CJD(4例确诊，3例临床很可能，1例临床可能)，比较其常规MRI及DWI检查结果。结果T1WI及LWI除4例显示脑萎缩外，未见异常信号；而8例DWI均异常，其中2例为单纯大脑皮层高信号改变，6例为大脑皮层合并尾状核、壳核高信号改变，5例呈对称性，3例呈非对称性；1例液体衰减反转恢复(FLAIR)序列成像显示大脑皮层呈稍高信号，但不如DWI明显。结论DWI显示的大脑皮层和(或)纹状体的高信号改变是CJD的特征之一，其诊断价值明显优于常规MRI，是早期诊断CJD的重要方法。     

MR imaging of familial Creutzfeldt-Jakob disease: a blinded and controlled study

BACKGROUND AND PURPOSE: The E200K mutation of the PRNP (prion protein) gene is the most common cause of familial Creutzfeldt-Jakob disease (fCJD), which has imaging and clinical features that are similar to the sporadic form. The purpose of this study was to conduct a controlled and blinded evaluation of the sensitivity and specificity of MR imaging in this unique population.MATERIALS AND METHODS: We compared the MR imaging characteristics of 15 early stage familial CJD patients (age, 60 ± 7 years) with a group of 22 healthy subjects from the same families (age, 61 ± 8 years). MR imaging included diffusion-weighted imaging (DWI), T2-weighted fast spin-echo imaging, and a fluid-attenuated inversion recovery (FLAIR) sequence. The scans were rated for abnormalities by an experienced neuroradiologist blind to diagnosis, group assignment, age, and sex.RESULTS: Thirteen of 15 fCJD subjects had abnormal MR imaging. FLAIR signal intensity abnormality in the caudate or putamen nuclei demonstrated a sensitivity of 87% and specificity of 91%. DWI abnormality in the caudate nucleus showed a sensitivity of 73% and a specificity of 100%. Abnormalities in the thalamus (6 patients), cingulate gyrus (6 patients), frontal lobes (4 patients), and occipital lobes (3 patients) were best detected with DWI. No signal intensity abnormalities were demonstrated in the cerebellum. T2-weighted and T1-weighted sequences were uninformative.CONCLUSIONS: FLAIR and DWI abnormalities in the caudate nucleus and putamen offer the best sensitivity and specificity for diagnosing fCJD. Our findings support recent recommendations that MR imaging should be added to the diagnostic evaluation of CJD.

Creutzfeldt-Jakob disease (CJD) is the most common human prion disease. It is a rare neurodegenerative disorder that is progressive and invariably fatal, with nearly 90% of patients dying within 1 year of diagnosis.¹ CJD occurs in approximately 1 person per 1 million people per year worldwide.¹ The most common form is sporadic CJD (sCJD), which occurs randomly without a known risk factor and accounts for 85%-90% of cases. Familial or hereditary CJD (fCJD), seen in 5%-10% of cases, is caused by mutations in the gene that controls formation of the normal prion protein on chromosome 20.¹ The most common pathogenic mutation is the E200K mutation. The risk of fCJD is transmitted in an autosomal dominant inheritance pattern, with nearly 100% penetrance.²The imaging findings in sCJD typically consist of cortical atrophy and hyperintensities in the basal ganglia, thalamus, and cortex on fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted imaging (DWI).^3–13 fCJD has imaging findings and neuropathology that are, in general, similar to the most common forms of sCJD; however, most imaging studies on fCJD consist primarily of case reports or studies focused on sCJD that combine a few fCJD patients into a single CJD patient sample.^8,14–22 fCJD studies are limited not only by small sample sizes but also by nonstandardized imaging protocols and clinical and pathophysiologic heterogeneity. The complex interactions with disease duration and cognitive and neurologic severity have also made it difficult to interpret studies, especially because the sample sizes are small.²³To address the difficulties of clinical research in this area, we initiated a study of fCJD occurring among Libyan Jews living in Israel that is caused by familial transmission of the E200K mutation.^24–26 In a preliminary report, it was demonstrated that 4 patients with fCJD due to the E200K mutation had gray matter atrophy and decreased apparent diffusion coefficient (ADC) in the basal ganglia. Signal intensity hyperintensities were seen in the basal ganglia and thalamus with FLAIR and DWI.²⁷ The sample size in that study was insufficient to calculate sensitivity and specificity. Here we describe a rigorously blinded and controlled evaluation of MR imaging findings in a larger number of fCJD patients.     

Diffusion abnormality of deep gray matter in external capsular hemorrhage

BACKGROUND AND PURPOSE: To our knowledge, diffusion abnormality of the unaffected deep gray matter during striatocapsular hemorrhage has not been previously described in the literature. We report the presence of the diffusion abnormality separated from hematoma in patients with external capsular (lateral striatocapsular) hemorrhage and suggest the plausible mechanisms of diffusion signal intensity change. METHODS: We retrospectively reviewed MR images in 28 consecutive patients with spontaneous striatocapsular hemorrhage and evaluated signal intensity changes at sites separated from the hemorrhage and the lesions on diffusion-weighted (DW) images. Apparent diffusion coefficients (ADCs) of the lesions were measured, and volume changes in the deep gray matter were assessed at follow-up. RESULTS: On DW images, hyperintensity of deep gray matter was found in nine patients (25%). In all patients with DW imaging abnormality, the hemorrhage was located in the external capsule, and the interval from hemorrhagic ictus to MR imaging study was 8-54 days. Hyperintensity of the deep gray matter was seen in the caudate (n = 8), putamen (n = 7), thalamus (n = 5), and substantia nigra (n = 2). Mean relative ADC ratios of the diffusion abnormality were 0.76 +/- 0.10 in the caudate, 0.79 +/- 0.07 in the putamen, and 0.85 +/- 0.11 in the thalamus. DW imaging abnormality disappeared with mild atrophy in two patients who underwent follow-up imaging. CONCLUSION: External capsular hemorrhage may be uncommonly accompanied by diffusion abnormality in the striatum or thalamus at follow-up, and the lesion should not be misdiagnosed as new-onset infarction. Secondary neuronal degeneration may play an important role in the development of diffusion abnormality.     

1例Creutzfeldt-Jakob病的神经影像学与脑电图长期跟踪研究

目的探讨散发性Creutzfeldt-Jakob病(sCJD)患者神经影像学、脑电图的特点和动态规律性。方法利用CT、MRI以及动态脑电图设备先后对1例病理确诊的sCJD患者行5次神经影像学和6次脑电图监测,并分析其规律性。结果①在辅助诊断CJD方面,弥散加权像(DWI)较头颅CT、常规MRI的T1加权像(T1WI)、T2加权像(T2WI)、FLAIR像以及MRI增强扫描更敏感;②CJD患者DWI表现为双侧底节区及皮层的异常高信号;病程晚期,皮层DWI异常信号可以消失;③CJD患者脑电图周期性尖慢复合波(PSD)的出现有明显的病程区间性及正弦曲线性特征;PSD在病程早期可以不出现,病程晚期可以消失。结论反复监测DWI和脑电图,对于确诊CJD是十分重要的。     

Diffusion-weighted MR imaging of subdural empyemas in children

BACKGROUND AND PURPOSE: Subdural empyema (SDE), an infection of the subdural space, occurs most often in pediatric patients as a complication of meningitis, sinusitis, or otitis media. Diffusion-weighted imaging (DWI) has been used in the past to investigate intracerebral infections. The purpose of this study was to determine the signal intensity characteristics of SDE on DWIs as well as the corresponding apparent diffusion coefficient (ADC) maps. METHODS: MR studies of 10 patients with SDEs were retrospectively reviewed. Included were routine sequences and DWI, which consisted of an axial single-shot echo-planar spin-echo sequence (TR/TE, 4000/110) with b values of 0, 500, and 1000 s/mm(2). Signal-intensity characteristics on routine MR images and DWIs were evaluated. In seven patients, ADC values of the lesions were calculated by using two b values. Follow-up imaging study was performed in seven patients. RESULTS: In nine patients, the empyema was hyperintense on DWIs. In the remaining patient, the empyema showed mixed hyperintensity and hypointensity. ADC values were lower than those of normal cortical gray matter and much lower than those of reactive subdural effusions. In all seven patients with persistent clinical signs of infection, the empyemas were hyperintense on follow-up DWIs. CONCLUSION: SDE had high signal intensity on DWIs and low signal intensity on ADC maps, with an ADC value lower than that of the normal cortical gray matter. Diffusion MR imaging can be valuable in distinguishing SDE from effusion and in the follow-up of subdural collections.     

Pattern of cortical changes in sporadic Creutzfeldt-Jakob disease

BACKGROUND AND PURPOSE: High cortical signal intensity on diffusion-weighted (DW) or fluid-attenuated inversion recovery (FLAIR) images is increasingly described in sporadic Creutzfeldt-Jakob disease (sCJD). The aim of this study was to assess the extent and location of high cortical signal intensity, to investigate whether DW or FLAIR is superior in showing changes in cortical signal intensity, and to find out whether the distribution of the signal intensity changes is random or follows a common pattern. MATERIALS AND METHODS: We analyzed FLAIR and DW MR imaging scans of 39 patients with sCJD for hyperintense cortical signal intensity. We compared the sensitivity of the DW and FLAIR scans. We correlated the extent and location of the cortical signal intensity changes with concomitant changes in deep gray matter and the genotype of codon 129 of the prion protein gene. RESULTS: There was high signal intensity in the insula, the cingulate gyrus, and the superior frontal gyrus in 95%. The cortical areas near the midline also frequently showed the abnormal signal intensity (precuneus 87%, paracentral lobe 77%). The precentral and postcentral gyri were affected less frequently (41% and 28%, respectively). The DW MR imaging showed the cortical changes more effectively than FLAIR. There was no correlation between the distribution of changes and additional signal alterations in deep gray matter or the genotype of codon 129. CONCLUSION: The distribution of cortical signal intensity abnormalities in patients with sCJD follows a common pattern, affecting mainly the cortical areas near the midline, the insula, cingulum, and the superior frontal cortex. DW imaging is superior to FLAIR in the detection of cortical high signal intensity.     

Creutzfeldt-jakob disease involvement of rolandic cortex: a quantitative apparent diffusion coefficient evaluation

BACKGROUND: Previous reports have suggested that abnormally reduced water diffusivity and T2 prolongation involving cerebral gray matter in patients with early sporadic Creutzfeldt-Jakob disease (sCJD) involves all areas of neocortex with similar frequency, except for primary sensorimotor cortex (Rolandic cortex) and visual cortex. Rolandic cortex often appears to be spared even in the presence of extensive surrounding neocortical signal intensity abnormality in adjacent frontal and parietal gray matter. A quantitative apparent diffusion coefficient (ADC) analysis was designed to investigate whether this unusual pattern results from pathophysiologic sparing of Rolandic cortex or from reduced conspicuity of signal intensity abnormality on MR imaging echo-planar diffusion-weighted images (epiDWI) related to unknown underlying features of Rolandic cortex. METHODS: ADC maps were derived from epiDWI of 6 patients with sCJD and 8 control patients. Bilateral regions of interest were manually selected in precentral gyri, superior frontal gyri, postcentral gyri, supramarginal gyri, thalamus, putamen, and caudate nuclei. ADC and relative ADC (rADC) values were calculated for each region of interest. RESULTS: Patients with CJD had significantly lower ADC values than control patients in all areas (P < or = 0.05). The trend toward decreased ADC values in the deep nuclei correlates well with previously published reports. rADC were not significantly different between CJD and control groups in any area (P > 0.25 in all cases). CONCLUSION: Quantitative ADC measurements in patients with early sCJD demonstrate a similar degree of reduced water diffusivity in the primary somatosensory cortex as in other neocortical areas, despite the normal appearance of these areas on visual inspection of epiDWI.     

多发性硬化患者脑灰质损害的MRI表现及扩散张量成像定量研究

目的 分析多发性硬化(MS)患者脑灰质病灶的MRI特征及表现正常的脑灰质(NAGM)是否存在隐匿性损伤.方法 对34例临床确诊的MS患者(MS组)和25名健康志愿者(对照组)行常规头颅MRI和扩散张量成像(DTI),观察MS的脑灰质病灶特征,测量深部灰质核团的平均扩散率(ADC)和各向异性分数(FA),采用非配对t检验比较两组间是否存在差异.结果 MR检查发现MS的脑灰质病灶共83个,占全部病灶(443个)的18.7%.分布以额叶最多,其次是颞叶与丘脑.大多数病灶呈圆形或类圆形,其中T2WI发现灰质病灶60个,液体衰减反转恢复(FLAIR)序列T2WI发现病灶78个,其中71个病灶呈高或稍高信号,3个病灶呈中心低、周围稍高的环形改变,4个呈低信号.扩散加权成像(DWI)发现高信号或低信号病灶36个,其中有9个小病灶在DWI呈明显高信号.其余病灶呈等信号而不能被发现.MS组尾状核头、壳核、丘脑的ADC值分别为(8.0±0.7)、(7.4 ±0.5)、(7.7±0.4)×10-4mm2/s,均高于对照组[分别为(7.4±0.6)、(7.0 ±0.5)、(7.2±0.7)×10-4mm2/s],差异具有统计学意义(t值分别为-3.079、-2.564、-2.722,P值均<0.05).结论 MS的脑灰质病灶在常规MRI和DWI上的表现有一定的特征,FLAIR联合DWI可提高病灶的检出,DTI可以反映出NAGM内的隐匿性损害.     

Magnetic resonance imaging and histologic findings of experimental cerebral fat embolism

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether cerebral fat embolism demonstrated reversible or irreversible findings in magnetic resonance (MR) imaging over time and to compare the features in MR images with histologic findings in a cat model. MATERIALS AND METHODS: MR images were obtained serially at 2 hours, 1 and 4 days, and 1, 2, and 3 weeks after embolization with 0.05 mL of triolein into the internal carotid artery in 19 cats. Any abnormal signal intensity and change in the signal intensity were evaluated on T2-weighted images, T1-weighted images, diffusion-weighted images (DWIs; including apparent diffusion coefficient [ADC] maps), and gadolinium-enhanced T1-weighted images (Gd-T1WI) over time. After MR imaging at 3 weeks, brain tissue was obtained and evaluated for light microscopic (LM) examination using hematoxylin-eosin and Luxol fast blue staining. For electron microscopic examination, the specimens were obtained at the cortex. The histologic and MR findings were compared. RESULTS: The embolization lesions showed hyperintensity on T2-weighted images, hyperintensity, or isointensity on DWIs, hypointensity, or isointensity on ADC maps and contrast enhancement on Gd-T1WIs at 2 hours. The T2-weighted hyperintensity extended to the white matter at day 1 and decreased thereafter. Contrast enhancement decreased continuously from day 1, and hyperintensity on DWI decreased after day 4. Hypointensity on ADC maps became less prominent after day 4. By week 3, most lesions had reverted to a normal appearance on MR images and were correlated with LM findings. However, small focal lesions remained in the gray matter of 8 cats and in the white matter of 3 cats on MR images, and this correlated with the cystic changes on LM findings. Electron microscopic examination of the cortical lesions that reverted to normal at week 3 in MR images showed that most of these lesions appeared normal but showed sporadic intracapillary fat vacuoles and disruption of the endothelial walls. CONCLUSIONS: The embolized lesions of the hyperacute stage were of 2 types: type 1 lesions, showing hyperintensity on DWIs and hypointensity on ADC maps, have irreversible sequelae, such as cystic changes; whereas type 2 lesions, showing isointensity or mild hyperintensity on DWIs and ADC maps, reverted to a normal appearance in the subacute stage.     

MR imaging of hypoglycemic encephalopathy: lesion distribution and prognosis prediction by diffusion-weighted imaging

Introduction

The aim of this study was to evaluate the patterns of hypoglycemic encephalopathy on diffusion-weighted imaging (DWI) and the relationship between the imaging patterns and clinical outcomes.

Methods

This retrospective study included 17 consecutive patients that had hypoglycemic encephalopathy with DWI abnormalities. The topographic distributions of the DWI abnormalities of the cortex, deep gray matter, and white matter structures were assessed. In addition, possible correlation between the patterns of brain injury on DWI and clinical outcomes was investigated.

Results

There were three patterns of DWI abnormalities: involvement of both gray and white matter (n?=?8), selective involvement of gray matter (n?=?4), and selective involvement of white matter (n?=?5). There was no significant difference in the initial blood glucose levels among patients for each of the imaging patterns. Most patients (16/17) had bilateral symmetrical abnormalities. Among patients with bilateral symmetrical gray and/or white matter injuries, one had moderate to severe disability and 14 remained in a persistent vegetative state. The two patients with a focal unilateral white matter abnormality and a localized splenial abnormality recovered without neurological deficits.

Conclusion

The results of this study showed that white matter was more sensitive to hypoglycemia than previously thought and there was no specific association between the patterns of injury and clinical outcomes whether the cerebral cortex, deep gray matter, and/or white matter were affected. Diffuse and extensive injury observed on the DWI predicts a poor neurologic outcome in patients with hypoglycemic injuries.     

Isolated cortical signal increase on MR imaging as a frequent lesion pattern in sporadic Creutzfeldt-Jakob disease

BACKGROUND AND PURPOSE: Hyperintense basal ganglia on MR imaging support the diagnosis of sporadic Creutzfeldt-Jakob disease (CJD). Our aim was to study the frequency of patients with sporadic CJD presenting with and without characteristic basal ganglia lesions on MR imaging and to examine the corresponding patient characteristics.MATERIALS AND METHODS: Fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted images (DWI) of 55 patients with CJD were assessed for signal-intensity increase (FLAIR) or restricted diffusion (DWI) in 7 cortex regions and the basal ganglia, thalamus, and cerebellum. Patient characteristics as well as electroencephalography, CSF, and codon 129 genotype of the prion protein gene (PRNP) were correlated with the most frequent MR imaging lesion patterns.RESULTS: Two major lesion patterns were identified by DWI: cortex and basal ganglia involvement (two thirds) and isolated cortex involvement (one third). In the latter patient group, the cortex involvement was widespread (at least 3 regions affected in 89% on DWI) and usually included the frontal and parietal lobes (78%). The length of the disease course was significantly prolonged (median, 12 versus 5 months). No significant differences were observed concerning electroencephalography and CSF findings and codon 129 genotype distributions. Of 4 patients with normal MR imaging findings, the CSF was positive for the 14-3-3 protein in 3.CONCLUSION: A high number of patients with CJD present without basal ganglia lesions on MR imaging. Isolated cortex involvement on DWI and FLAIR should lead to suggestion of CJD, even if the disease course is only slowly progressive. Additional 14-3-3 protein analysis in the CSF may support the CJD diagnosis.

Sporadic Creutzfeldt-Jakob disease (CJD) is a rare and fatal disease caused by the accumulation of abnormal/pathologic prion protein (PrP^Sc; Sc indicates scrapie) in the human brain. The classic disease type is characterized by rapidly progressive dementia, ataxia, abnormal muscle tone, and myoclonus. It leads to a state of akinetic mutism and death after a median disease duration of 6 months.¹ The definite CJD diagnosis relies on the finding of PrP^Sc in the brain tissue, together with astrocytic gliosis, nerve cell loss, and spongiform degeneration as the typical neuropathologic changes.^2,3During one''s lifetime, MR imaging hyperintensity of the basal ganglia on T2-weighted (T2WI), fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI) is increasingly used to support the CJD diagnosis, next to positive CSF (14-3-3 protein) and electroencephalography (EEG) findings of periodic sharp-wave complexes (PSWCs). Although the origin of the signal-intensity changes is still not fully understood, hyperintensity on T2WI and FLAIR has been thought to be caused by gliosis, whereas abnormalities on DWI are most likely derived from spongiform changes.^4–6 DWI was shown to be the most sensitive sequence in the detection of brain lesions, particularly in the neocortex.^7–10 Isolated cortex involvement was also found.^9,11Although abnormal MR imaging findings in CJD have been studied in detail with respect to their location, few attempts have been made to define the most frequently occurring patterns of hyperintensity in a spectrum of patients. Six disease phenotypes (MM1, MM2, MV1, MV2, VV1, and VV2) defined by the codon 129 genotype (MM, MV, VV) of the prion protein gene (PRNP) and pathologic isotype of the PrP^Sc type 1 or 2 have been recently described with distinctive neuropathologic features and various clinical and diagnostic findings.^1–3,12 On MR imaging, predominant cortical (VV1)¹³ or subcortical involvement (MV2 and VV2)^14,15 or no abnormalities (MM2)^16,17 were found in smaller case series.To date, to our knowledge, the overall distribution of MR imaging abnormalities has not been studied in a larger spectrum of patients with CJD, and it is unclear whether there are clinical correlates corresponding to specific MR imaging lesion patterns. The proportion of patients presenting without basal ganglia abnormalities is unknown.We defined the most frequent MR imaging lesion patterns and corresponding clinical characteristics in a CJD patient collective by using highly sensitive MR images, and we considered a possible influence of the codon 129 genotype of the PRNP. We particularly focused on patients lacking basal ganglia abnormalities on MR imaging and suggested criteria that might support the early CJD diagnosis in these patients.     

用MR扩散加权成像评价新生儿缺氧缺血性脑病的初步研究

目的应用扩散加权成像(DWI)方法评价新生儿缺氧缺血性脑病(HIE)，并同常规MRI对照，以了解扩散成像的价值及限度。方法对临床确诊的36例缺氧缺血性脑病的新生儿(年龄3h至22d，平均8．44d)，进行常规MRT，WI和DWI检查(b=700s／mm^2)。观察皮层及皮层下白质、深部白质、基底节及丘脑、脑室及脑外间隙等部位。结果缺血缺氧所致脑损害在DWI表现为弥漫性损害：区域性皮层、皮层下及深部白质较广泛的高信号19．4％(7／36)；局灶性损害：沿侧脑室壁和三角部白质的高信号27．8％(10／36)，额叶深部白质点状高信号5．6％(2／36)。相应部位的T1WI分别为16．7％(6／36)，36．1％(13／36)，30．6％(11／36)。出血性病变，在T1WI上为高信号，而在DWI上表现为无信号。结论MR DWI适于早期检查HIE，T1WI适于亚急性期和慢性期。     

Cortical lesions in multiple sclerosis: combined postmortem MR imaging and histopathology

BACKGROUND AND PURPOSE: Cortical lesions constitute a substantial part of the total lesion load in multiple sclerosis (MS) brain. They have been related to neuropsychological deficits, epilepsy, and depression. However, the proportion of purely cortical lesions visible on MR images is unknown. The aim of this study was to determine the proportion of intracortical and mixed gray matter (GM)-white matter (WM) lesions that can be visualized with postmortem MR imaging. METHODS: We studied 49 brain samples from nine cases of chronic MS. Tissue sections were matched to dual-echo T2-weighted spin-echo (T2SE) MR images. MS lesions were identified by means of myelin basic protein immunostaining, and lesions were classified as intracortical, mixed GM-WM, deep GM, or WM. Investigators blinded to the histopathologic results scored postmortem T2SE and 3D fluid-attenuated inversion recovery (FLAIR) images. RESULTS: Immunohistochemistry confirmed 70 WM, eight deep GM, 27 mixed GM-WM, and 63 purely cortical lesions. T2SE images depicted only 3% of the intracortical lesions, and 3D FLAIR imaging showed 5%. Mixed GM-WM lesions were most frequently detectable on T2SE and 3D FLAIR images (22% and 41%, respectively). T2SE imaging showed 13% of deep GM lesions versus 38% on 3D FLAIR. T2SE images depicted 63% of the WM lesions, whereas 3D FLAIR images depicted 71%. Even after side-by-side review of the MR imaging and histopathologic results, many of the intracortical lesions could not be identified retrospectively. CONCLUSION: In contrast to WM lesions and mixed GM-WM lesions, intracortical lesions remain largely undetected with current MR imaging resolution.     

Intracortical lesions in multiple sclerosis: improved detection with 3D double inversion-recovery MR imaging

PURPOSE: To prospectively compare the depiction of intracortical lesions by using multislab three-dimensional (3D) double inversion-recovery (DIR), multislab 3D fluid-attenuated inversion-recovery (FLAIR), and T2-weighted spin-echo (SE) magnetic resonance (MR) imaging in patients with multiple sclerosis. MATERIALS AND METHODS: Local ethics review board approval and informed consent were obtained. Conventional T2-weighted SE and multislab 3D FLAIR and DIR images were acquired in 10 patients with multiple sclerosis (five women, five men) and 11 age-matched healthy control subjects (seven women, four men). Mean age was 40 years (range, 25-54 years) in patients and 34 years (range, 24-55 years) in control subjects. Lesions were classified according to seven anatomic regions: intracortical, mixed white matter-gray matter, juxtacortical, deep gray matter, periventricular white matter, deep white matter, and infratentorial lesions. The numbers of lesions per category were compared between techniques (Dunnett-corrected analysis of variance). Gain or loss (with 95% confidence intervals [CIs]) of numbers of lesions detected at 3D DIR imaging was calculated in comparison with those detected at T2-weighted SE and 3D FLAIR imaging. RESULTS: Total number of lesions did not differ between 3D DIR and 3D FLAIR sequences, but the 3D DIR sequence showed a gain of 21% (95% CI: 4%, 41%) in comparison with the T2-weighted SE sequence. Because of high gray matter-white matter contrast, DIR images depicted more intracortical lesions (80 lesions in 10 patients) than both SE (10 lesions) and FLAIR (31 lesions) images; gains with DIR were 538% (95% CI: 191%, 1297%) and 152% (95% CI: 15%, 453%) compared with SE and FLAIR, respectively. Only four intracortical lesions were detected in control subjects. Also, DIR imaging enabled a better definition of mixed white matter-gray matter lesions because of greater contrast between the lesion and its surroundings. CONCLUSION: MR imaging with 3D DIR enables increased intracortical lesion detection in the multiple sclerosis brain, as well as improved distinction between juxtacortical and white matter-gray matter lesions.     

Diffusion-weighted MR imaging in multiple sclerosis: comparison with contrast-enhanced study

OBJECTIVE: To assess the utility of cerebral diffusion-weighted MR imaging in the diagnosis of multiple sclerosis (MS) in comparison with contrast-enhanced T1-weighted imaging. METHODS AND MATERIALS: We reviewed T2-weighted spin-echo (SE), fluid-attenuated inversion-recovery (FLAIR), contrast-enhanced T1-weighted SE and echo-planar diffusion-weighted images (DWIs) obtained in seven patients with definite MS on nine occasions. RESULTS: In total, 94 plaques were demonstrated on T2-weighted SE and/or FLAIR images. A total of 13 of these plaques showed enhancement on contrast-enhanced T1-weighted images and hyperintensity on DWIs, and five non-enhancing plaques showed hyperintensity on DWIs. CONCLUSION: Diffusion-weighted imaging, which provides information based on pathophysiology different from contrast-enhanced imaging, is a potential supplementary technique for characterizing MS plaques.     

Normal myelination of the pediatric brain imaged with fluid-attenuated inversion-recovery (FLAIR) MR imaging.

BACKGROUND AND PURPOSE: As in adult imaging, FLAIR can be applied to pediatric brain imaging, and this requires an appreciation of the normal pediatric brain appearance by FLAIR imaging. The purpose of this study was to describe the MR appearance of the brain in normal infants and young children as demonstrated by fluid-attenuated inversion-recovery (FLAIR) MR imaging. METHODS: We retrospectively examined MR brain studies, interpreted as normal by pediatric radiologists, from 29 patients (aged 1 to 42 months) to catalog the appearance of myelination in multiple brain areas. RESULTS: On T2-weighted images, white matter progressed from hyperintense to hypointense relative to adjacent gray matter over the first 2 years of life. An analogous, although slightly delayed sequence was observed on FLAIR images with the exception of the deep cerebral hemispheric white matter, which followed a triphasic sequence of development. On FLAIR images, the deep cerebral white matter was heterogeneously hypointense relative to gray matter in the young infant, became hyperintense early in the first few months of life, and then reverted to hypointense during the second year of life. CONCLUSION: The normal appearance and development of brain white matter must be taken into account when interpreting FLAIR images of infants and young children.     

Diffusion-weighted imaging and fluid attenuated inversion recovery imaging in the evaluation of primitive neuroectodermal tumors

The aim of our study was to determine whether fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI) would be helpful in characterizing primitive neuroectodermal tumors (PNET) from other pediatric brain tumors. We expected that the compact cellular nature and the relatively small extracellular space of this tumor would affect the signal intensity on both pulse sequences relative to the more sparsely cellular glial tumors that have larger extracellular spaces. Eighteen pediatric patients with PNET were examined on a 1.5 T MRI with routine imaging plus FLAIR and compared with 28 patients with non-PNET. DWI was also performed in 7 PNET and 18 non-PNET. Seventy-eight percent of PNET were isointense to gray matter on FLAIR while 82 % of non-PNET were hyperintense and only one was isointense (3 %). Diffusion was abnormally restricted in all 7 PNET examined (100 %) but was restricted in non-PNET in only 1 out of 18 (6 %) patients who had DWI. The differences in the histologic architecture between PNET and non-PNET are reflected in both FLAIR imaging and in DWI. Received: 3 February 2001/Accepted: 13 February 2001