Wallerian degeneration of the middle cerebellar peduncle after pontine infarction: MR imaging

PURPOSE: To report magnetic resonance (MR) imaging findings of wallerian degeneration of the pontocerebellar tract secondary to a pontine infarction. MATERIALS AND METHODS: We retrospectively reviewed cranial MR images obtained during the past seven years in our institution and selected those from patients with a chronic stage of pontine infarction and a hyperintense lesion at the central portion of the middle cerebellar peduncle on T2-weighted images. RESULTS: In three patients with a ventromedial pontine infarction, we found a symmetrical hyperintense lesion at the central portion of the middle cerebellar peduncle bilaterally on T2-weighted MR images in the chronic stage. In another patient with a ventrolateral pontine infarction, we found such a lesion at the ipsilateral middle cerebellar peduncle. CONCLUSION: Because the middle cerebellar peduncle carries afferent fibers from the contralateral basis pontis to the cerebellar cortex, these middle cerebellar peduncular lesions are regarded as wallerian degeneration. This secondary degeneration should not be misinterpreted as a newly developed infarction or other disease.     

MR imaging of wallerian degeneration in the human brain stem after ictus

Summary Magnetic resonance (MR) imaging of wallerian degeneration in the brain stem was studied in 30 hemiplegic patients within 12 months of ictus. As early as 25 days after the ictus, decreased signal intensities on proton-density (PD)-weighted images were observed in the brain stem ipsilaterally. This hypointensity gradually approached an isointense stage during 70–80 days after the ictus, abnormal intensities were not detected in any pulse sequence. We termed this phenomenon Fogging effect of wallerian degeneration. In later stages, at least 81 days after the ictus, increased signal intensities on T2-weighted images, with or without decreased signal intensities on T1-weighted images, were observed in the brain stem, ipsilaterally. Finally, at least six months after the ictus, mild shrinkage of the ipsilateral brain stem was newly detected on the T1-weighted images. MR imaging has proven to be a sensitive diagnostic modality for evaluating wallerian degeneration in the brain stem.     

Fogging effect and MR imaging: a case report of pontine infarction

We used serial MR imaging to examine a pontine infarct in an aged man. The fogging effect was observed on the images obtained 12 days after ictus. Knowledge of the fogging effect is important for a correct interpretation of MR imaging.     

MR imaging of central pontine myelinolysis

Central pontine myelinolysis is a demyelinating disorder with characteristic magnetic resonance features. Findings on T1-weighted scans include a symmetric region of low signal involving the basilar pons with sparing of the descending corticospinal tracts as well as the peripheral pontine tissues. The T2-weighted images show an area of high signal corresponding to the abnormal region identified on T1-weighted scans. Associated extrapontine demyelinating lesions are also demonstrated.     

MR imaging of pontine and extrapontine myelinolysis

Two cases of pontine and extrapontine myelinolysis following electrolyte derangements are presented. One case showed only extrapontine myelinolytic lesions on magnetic resonance (MR) imaging, although both pontine and extrapontine myelinolysis were confirmed at postmortem. Another case made full recovery clinically with resolution of extrapontine lesions on MR imaging.     

Signal intensity of the normal pontine tegmentum on T2-weighted MR imaging

On T2-weighted MR images, the pontine tegmentum frequently shows a signal of high intensity in neurologically healthy individuals. We examined whether the signal intensity of the pontine tegmentum normally differs from that of the pontine base. We evaluated the signal intensity of the pontine tegmentum and pontine base on T2-weighted images from 38 neurologically healthy subjects. The subjects included 29 adults (16 males and 13 females, age range 23-48 years, mean age 39.5 years) and 9 children (4 boys and 5 girls (age range 4-9 years mean age 6.5 years). We compared the contrast-to-noise ratio (CNR) between the tegmentum and the base in the upper pons, midpons and lower pons, and evaluated the signal intensity ratio of the tegmentum to the base. The CNR was significantly higher for the tegmentum than the base at each level of the pons (P<0.0001), and the signal intensity ratio of the tegmentum to the base in the upper pons was significantly higher in children than in adults (P<0.005). On T2-weighted images, a high signal intensity of the pontine tegmentum is frequently seen in neurologically healthy subjects. This finding should not be considered abnormal, particularly in children.     

MR imaging of medullary infarction

Magnetic resonance (MR) images of 20 patients with medullary infarction have been reviewed. All patients were imaged on a 1.5 Tesla high-field scanner (GE, Signa). Clinical diagnoses of these 20 patients were Wallenberg's syndrome (15), cerebellar infarct (3), right hemiparesis (1), and multiple cerebral infarcts (1). Locations of infarct were right lateral (8), right postero-lateral (2), left lateral (5), left postero-lateral (4) and left anterior (1). Associated ipsilateral cerebellar infarcts were observed in six patients. Ipsilateral vertebral artery (VA) occlusions were detected in six patients, and VA aneurysm in two. Thus, MR imaging is a pertinent diagnostic modality for evaluating medullary infarction and associated vascular diseases.     

Dichotomy between clinical findings and MR abnormalities in pontine infarction

Comparison between cranial CT and magnetic resonance (MR) imaging in 10 patients with recent pontine infarction indicates a distinct superiority for MR. However, MR changes often failed to correlate with the degree of neurological dysfunction. Regions of abnormal signal intensity appeared to involve areas with normal neurologic function.     

脑梗死后出血性转变的CT、MRI比较

目的 探讨CT、MRI对脑梗死后出血性转变(HT)的诊断价值,并对其特征性表现进行比较.方法 回顾性分析60例HT患者的CT、MRI表现,依据欧洲急性中风合作研究(ECASS)分型进行CT分型,参照该分型,根据MRI显示的脑梗死病变内出血灶的异常信号范围进行MRI分型,并进行HT的CT、MRI比较.结果 MRI检出HT例数明显多于CT,尤其是对出血性脑梗死(HI)的检出,MRI发现了HI 52例(86.7%)而CT仅7例(11.7%),差异有统计学意义(P＜0.005).对脑实质出血(PH)的显示,二者检出率比较无明显差别.MRI可以检出CT不易发现的微小岀血及亚急性期、慢性期岀血及幕下出血.CT显示的HT的数目、大小、范围较MRI小.同一病例MRI与CT显示的HT形态可能不同.结论 MRI诊断HT较CT更敏感,2种分型方法得出的结论不同.MRI分型对判断出血分期、指导临床治疗和判断预后有重要意义.     

Wallerian degeneration after cerebral infarction: evaluation with sequential MR imaging

The dynamic signal intensity changes at magnetic resonance (MR) imaging in active and chronic wallerian degeneration in the corticospinal tract were evaluated. Forty-three patients with wallerian degeneration seen on MR images after cerebral infarction were studied. When possible, patients with acute stroke were examined with MR imaging prospectively at the onset of symptoms and then at weekly intervals for several months. Focal infarction without distal axonal degeneration is demonstrated for the 1st month following onset of clinical symptoms. At 4 weeks, a well-defined band of hypointense signal appears on T2-weighted images in the topographic distribution of the corticospinal tract. After 10-14 weeks, the signal becomes permanently hyperintense. Over several years, accompanying ipsilateral brain stem shrinkage occurs. The dark signal intensity observed on T2-weighted images between 4 and 14 weeks is believed to result primarily from transitory increased lipid-protein ratio.     

Spatially resolved imaging of myocardial function with strain-encoded MR: comparison with delayed contrast-enhanced MR imaging after myocardial infarction

Strain-encoded magnetic resonance (MR) imaging was prospectively evaluated for direct imaging of systolic myocardial strain and compared with cross-registered delayed contrast material-enhanced MR imaging in five healthy volunteers and nine patients with infarction. Local contractile performance was decreased in infarcted myocardium versus that in remote and adjacent myocardium (P < .01) and in adjacent versus remote myocardium (P < .05). The extent of dysfunctional myocardium, as assessed with strain-encoded MR imaging, was greater than that of hyperenhancement, as assessed with delayed contrast-enhanced MR imaging (P < .05). Strain values obtained with strain-encoded MR imaging were strongly correlated with those obtained with three-dimensional tagged MR imaging (r = 0.75, P < .001). Strain-encoded MR imaging provides spatially resolved (1.5 x 2.5-mm) imaging and measurement of myocardial strain in humans without the need for postprocessing, which may improve routine comprehensive evaluation of myocardial viability.     

MR imaging of acute hemorrhagic brain infarction

Six patients with acute hemorrhagic brain infarct were imaged using spin-echo (SE) pulse sequences on a 1.5 Tesla MR scanner. Including two patients with repeated MR imaging, a total of eight examinations, all performed within 15 days after stroke, were analyzed retrospectively. Four patients revealed massive hemorrhages in the basal ganglia or cerebellum and three cases demonstrated multiple linear hemorrhages in the cerebral cortex. On T1-weighted images, hemorrhages were either mildly or definitely hyperintense relative to gray matter, while varied from mildly hypointense to hyperintense on T2-weighted images. T1-weighted images were superior to T2-weighted images in detection of hemorrhage. CT failed to detect hemorrhages in two of five cases: indicative of MR superiority to CT in the diagnosis of acute hemorrhagic infarcts.     

脑桥中央髓鞘溶解症的MR影像诊断(附三例分析)

目的研究脑桥中央髓鞘溶解症（ｃｅｎｔｒａｌｐｏｎｔｉｎｅｍｙｅｌｉｎｏｌｙｓｉｓ,ＣＰＭ）的ＭＲＩ特征。方法回顾性分析３例ＣＰＭ患者的ＭＲＩ表现,总结ＭＲＩ诊断与鉴别诊断要点。结果ＣＰＭ的ＭＲＩ特征表现为：（１）病变位于脑桥中央部位,主要累及桥横纤维的髓鞘,皮质脊髓束的轴索保持完好;（２）病灶多表现为环形或蝴蝶样,边缘模糊;（３）Ｔ１ＷＩ病灶呈低信号强度影,Ｔ２ＷＩ则为高信号影;（４）病变的早期阶段可见病灶内有斑点样高信号强度影;（５）静脉注入造影剂ＧｄＤＴＰＡ后,可见病灶边缘轻度增强。结论ＭＲＩ是ＣＰＭ的最好检查方法,当有上述表现时高度提示ＣＰＭ的可能     

静脉性脑梗死MR影像特点

目的回顾总结静脉性脑梗死MRI及MRV影像表现,旨在提高影像诊断水平。方法对15例静脉性脑梗死的MR表现进行了回顾性分析,其中9例临床治疗后复查MR表现明显好转,临床症状明显改善。15例均行常规MRI平扫,其中9例同时进行MR增强及3DCE-MRV,6例行2DTOF MRV。结果 15例脑内多发病灶9例,单发病灶6例,其中2例脑梗死伴出血改变。15例中发生于额叶4例,顶叶6例,颞叶3例,枕叶1例,小脑1例。静脉栓塞部位11例为上矢状窦,1例直窦及左横窦,1例右侧横窦及乙状窦,2例皮层大脑浅静脉。9例行增强扫描,5例病灶内不规则强化,2例脑膜强化,3例无强化.7例MRV均显示栓塞的静脉血流信号丢失或缺损,3例出现异常静脉侧支或引流静脉异常扩张。结论静脉性脑梗死MR影像表现具有特征性,MRI结合MRV可以作为首选的无创检查方法,对静脉栓塞早期诊断和治疗有重要作用。     

MR imaging of spontaneous spinal cord infarction

Magnetic resonance imaging was utilized to evaluate three women, one of whom was pregnant, with a clinical diagnosis of anterior spinal artery syndrome. In each case, development of spinal cord infarctions was spontaneous. Sagittal and axial MR images of the spine were obtained prior to and following administration of Gd-diethylenetriamine pentaacetic acid. Magnetic resonance showed no cord enlargement or signal abnormality on T1-weighted images prior to contrast medium administration. On T2-weighted images there was abnormal increase in signal intensity in the cord at levels corresponding to the neurologic deficits in all three patients. Variable contrast enhancement was demonstrated in these areas. Magnetic resonance imaging was positive, whereas CT-myelography, carried out in the two nonpregnant women, failed to demonstrate any abnormalities.     

胼胝体梗死的MRI诊断

目的：探讨MRI对胼胝体梗死的诊断价值,提高对胼胝体梗死的MRI表现及临床意义的认识。方法：回顾性分析25例胼胝体梗死患者的MRI和临床表现资料,男14例,女11例,年龄17～82岁,平均53．8岁。全部病例均以肢体无力、言语不清、意识障碍或反应迟钝就诊。所有患者均行常规颅脑MRI平扫,3例同时行MRI增强扫描,2例治疗后复查了MRI。结果：所有患者均存在胼胝体梗死,T1WI表现为低信号,T2WI及FLAIR为高信号,局限或弥漫性分布,波及胼胝体全层。病灶位于压部11例、膝部3例、体部1例;同时累及膝部及体部4例、体部及压部1例;单侧胼胝体全程受累5例。梗死灶沿胼胝体偏侧性分布（22例）明显多于对称性分布（3例）,差异有统计学意义（Х^2=7．260,P〈0．05）。3例梗死灶增强扫描未见明显强化;2例治疗后复查MRI提示病灶明显缩小。结论：胼胝体梗死是临床急症之一,MRI可直观反映梗死灶部位及范围,是临床诊断胼胝体梗死最客观的参考指标。     

脑桥中央髓鞘溶解症MRI表现(附4例报告)

目的:探讨脑桥中央髓鞘溶解症(central pontine myelinolysis,CPM)磁共振成像特点。方法:回顾分析我院经临床及影像学检查确诊的4例CPM患者的MRI表现,总结其诊断及鉴别要点。结果:CPM的MRI表现:①T1WI病灶呈低信号,T2WI为高信号影;②病灶多为蝴蝶形或环形;③病变位于脑桥中央,皮质脊髓束的轴索无损害。结论:脑桥中央髓鞘溶解症MRI表现有一定特征性,根据MRI可做出正确诊断。     

High-b-value diffusion-weighted MR imaging of suspected brain infarction

BACKGROUND AND PURPOSE: Recent technological advances in MR instrumentation allow acquisition of whole-brain diffusion-weighted MR scans to be obtained with b values greater than 1,000. Our purpose was to determine whether high-b-value diffusion-weighted MR imaging improved contrast and detection of signal changes in acute and chronic brain infarction. METHODS: We prospectively evaluated the MR scans of 30 subjects with a history of possible brain infarction on a 1.5-T MR imager with 40 mT/meter gradients (slew rate 150 T/m/s) by use of the following single-shot echo-planar diffusion-weighted MR sequences: 1) 7,999/ 71.4/1 (TR/TE/excitations, b = 1,000; 2) 999/ 88.1/3, b = 2,500; and 3) 7,999/ 92.1/4, b = 3,000. Diffusion-weighted MR imaging was performed in three orthogonal directions during all sequences. All subjects were scanned with fast fluid-attenuated inversion recovery (FLAIR) (10,006/145/2,200/1 [TR/TE/TI/excitations]) and fast spin-echo T2-weighted (3,650/95/3 [TR/TE/excitations], echo train length, 8). The diagnosis of brain infarction was established by clinical criteria. RESULTS: Twenty women and 10 men with a mean age of 67.7 years were enrolled in the study. One subject was excluded owing to poor image quality. Twelve of 29 subjects had a clinical diagnosis of acute infarction. All 12 had lesions that were hyperintense on diffusion-weighted images at all three b values; five were cortical and seven subcortical. There was increased contrast of all lesions on high-b-value scans (b = 2,500 and 3,000). Lesions that were hypointense on diffusion-weighted images were identified and evaluated at the three different b values. At b = 1,000, there were 19 hypointense lesions, whereas at b = 2,500 and 3,000 there were 48 and 55 lesions, respectively. On FLAIR and T2-weighted images, these low-signal lesions were predominantly chronic, subcortical, ischemic lesions and lacunar infarcts, but four chronic cortical infarcts, one porencephalic cyst, and one primary brain tumor were also found. Low-signal lesions were also noted to have increased contrast on high-b-value diffusion-weighted scans. CONCLUSION: High-b-value diffusion-weighted MR imaging (b = 2,500 or b = 3,000) had no impact on diagnosis of acute infarction. High-b-value diffusion-weighted MR imaging (b = 2,500) combined with diffusion-weighted MR imaging at b = 1,000 improves tissue characterization by increasing the spectrum of observed imaging abnormalities in patients with suspected brain infarction.