Quantitative magnetic resonance imaging of the fetal brain in utero: Methods and applications

Application of modern magnetic resonance imaging(MRI) techniques to the live fetus in utero is a relatively recent endeavor. The relative advantages and disadvantages of clinical MRI relative to the widely used and accepted ultrasonographic approach are the subject of a continuing debate; however the focus of this review is on the even younger field of quantitative MRI as applied to non-invasive studies of fetal brain development. The techniques covered under this header include structural MRI when followed by quan-titative(e.g., volumetric) analysis, as well as quantita-tive analyses of diffusion weighted imaging, diffusion tensor imaging, magnetic resonance spectroscopy and functional MRI. The majority of the published work re-viewed here reflects information gathered from normal fetuses scanned during the 3rd trimester, with relatively smaller number of studies of pathological samples including common congenital pathologies such as ven-triculomegaly and viral infection.

Endovascular retrieval of a prematurely deployed covered stent

Several techniques have been reported to address different endovascular device failures. We report the case of a premature deployment of a covered balloon mounted stent during endovascular repair of a posttraumatic carotid-cavernous fistula(CCF). A 50-year-old male suffered a fall resulting in loss of consciousness and multiple facial fractures. Five weeks later, he developed decreased left visual acuity, proptosis, chemosis, limited eye movements and cranial/orbit bruit. Cerebral angiography demonstrated a direct left CCF and endovascular repair with a 5.0 mm × 19 mm covered stent was planned. Once in the lacerum segment, increased resistance was encountered and the stent was withdrawn resulting in premature deployment. A 3 mm × 9 mm balloon was advanced over an exchange length microwire and through the stent lumen. Once distal to the stent, the balloon was inflated and slowly pulled back in contact with the stent. All devices were successfully withdrawn as a unit. The use of a balloon to retrieve a prematurely deployed balloon mounted stent is a potential rescue option if leaving the stent in situ carries risks.

ANAGRAM PROBLEM-SOLVING AND LEARNING IN ANTERIOR PREFRONTAL CORTEX

We utilized Near-Infrared(NIR)spectroscopy to closely investigate the activation change in anterior prefrontal cortex(aPFC)during verbal anagram problem-solving and learning.We used a parametric design of anagram-solving with three difficulty levels and evaluated anagram skill with two sets of subjects and protocols.The first protocol was a one-time evaluation of untrained subjects(n=10)and the second protocol evaluated subjects over 6 weeks of training(n=6).The untrained subjects in the first protocol demonstrated blood oxygenation corresponding to neuronal activation in the aPFC in response to medium and hard difficulty levels of the stimuli,while the easy anagram task deoxygenated the aPFC bilaterally,corresponding to deactivation.Higher performers have more aPFC activation than lower performers in the medium difficulty level anagram-solving task.Six weeks of training in the second protocol showed that training reduced oxygenation in aPFC.In particular,subjects with lower baseline skill in anagram production showed a larger reduction in oxygenation where true performance gains occurred(medium difficulty)and smaller reduction where the performance gains were limited(hard anagrams).Association of the aPFC activation with the difficulty of the complex task suggests that aPFC is a part of a circuit for execution of task performance.In addition,more use of aPFC by untrained high performers suggests that the role of the aPFC is to increase efficiency of a problem-solving task.Thus,the NIR spectroscopy showed that the aPFC is a key structure in the circuit implementing the development of anagram skill.

齿状核MRI T2加权低信号与多发性硬化症患者步行能力损伤有关

Objectives: MRI T2 hypointensity in multiple sclerosis (MS)-gray matter, suggesting iron deposition, is associated with physical disability, disease course, lesion load, and brain atrophy. Ambulatory dysfunction limits quality of life; however correlation with conventional MRI remains poor. Methods: Normalized intensity on T2-weighted images was obtained in the basal ganglia, thalamus, red nucleus, and dentate nucleus in 47 MS patients and 15 healthy controls. Brain T1-hypointense and FLAIR-hype-rintense lesion volume, third ventricle width, brain parenchymal fraction and timed 25 foot walk (T25FW)-were measured in the MS group. Results: T2 hypointensity was present throughout gray matter in MS vs. controls (all p < 0.01). Dentate T2 hypointensity was the only MRI variable significantly correlated with T25FW (Pearson r=-0.355, p=0.007) and was also the best MRI correlate of physical disability (EDSS) score in regression modeling (r=-0.463, R2=0.223, p=0.004). Conclusions: T2 hypointensity is present in subcortical gray matter nuclei in patients with MS vs. normal controls. Dentate nucleus T2 hypointensity is independently related to ambulatory impairment and disability, accounting for more variance than conventional lesion and atrophy measures. This study adds more weight to the notion that T2 hypointensity is a clinically relevant marker of tissue damage in MS.

白质高信号的磁化传递成像

The severity of tissue changes associated with incidental white matter hyperintensities (WMH) in the elderly cannot be sufficiently determined by conventional MRI. We, therefore, performed a regional analysis of the magnetization transfer ratio (MTR) maps obtained on a 1.5 T scanner from 198 neurologically asymptomatic participants of the Austrian Stroke Prevention Study (mean age 70, age range 52-87 years) in regard to WMH and predefined areas of normal appearing brain tissue. Fluid attenuated inversion recovery MRI was used to grade lesion severity and for lesion volume measurements. The MTR of WMH was always significantly lower than that of normal appearing white matter (NAWM) with an overall relative reduction of 10%and decreased significantly with increasing scores of WMH severity (P = 0.02) and WMH volume (r = -0.24, P = 0.0016). NAWM MTR was not different between subjects with very few and extensive WMH and the WMH volume was associated with NAWM MTR of the frontal lobes only. Concerning a possible impact on cerebral functioning the MTR of the frontal NAWM was significantly associated with fine motor dexterity (P = 0.04) but not with cognitive performance. A significant decline of the MTR with aging was seen in both NAWM and cortex but not in WMH. We conclude that MTR measurements can serve to quantify WMH associated tissue damage. It is predominantly focal, relatively mild, increases with lesion size and may have remote effects on the frontal white matter.

Stroke-induced immunosuppression and poststroke infection

Infections occur commonly after stroke and are strongly associated with an unfavourable functional outcome of these patients.Approaches for effective management of poststroke infection remain scarce,presenting an urgent need for preventive anti-infection strategies for patients who have suffered a stroke.Emerging evidence indicates that stroke impairs systemic immune responses and increases the susceptibility to infections,suggesting that the modification of impaired immune defence could be beneficial.In this review,we summarised previous attempts to prevent poststroke infections using prophylactic antibiotics and the current understanding of stroke-induced immunosuppression.Further elucidation of the immune mechanisms of stroke will pave the way to tailored design of new treatment to combat poststroke infection via modifying the immune system.

常见神经系统症状的影像学检查指南

头痛、一过性神经系统症状、轻微头部外伤后的症状以及颈部和腰背痛是全科医生和急诊室医生经常面对的问题。接诊医生常常不确定是否该行神经系统影像学检查。本文中，我们将讨论这些情况下可能最有帮助的影像学和检查的指征。表1总结了我们解决这类问题的思路。图1显示了头痛或轻微头部外伤病人的代表性影像的一系列情况，包括正常和异常的结果。图2显示了这里描述的临床情况下相关的异常影像学结果的各种例子。