MR evaluation of wallerian degeneration of the pyramidal tract

This study is based on 135 magnetic resonance (MR) exams of 110 patients with wallerian degeneration of the pyramidal tract shown on MR images acquired on a mid field imaging scanner. The MR findings of wallerian degeneration were abnormal signal band along the course of the pyramidal tract and ipsilateral brain stem shrinkage. In all 110 cases an abnormal signal band was seen on T2-weighted spin-echo images, that is, a hypointense band in four exams between 30 days and 116 days after onset of symptoms, and hyperintense bands in 122 exams. The hyperintense signal on T2-weighted images was shown in most cases after 200 days from the onset. In one case a signal of the pyramidal tract showed a hyperintense band at 7 days, hypointense at 30 days, and hyperintense again at 123 days after onset. Sequential MR exams of another case showed gradual narrowing of the hyperintense signal band and progression of the ipsilateral brainstem shrinkage. The narrowing of the pyramidal tract and the ipsilateral brain stem shrinkage tended to be shown after 6 months from onset.(ABSTRACT TRUNCATED AT 250 WORDS)     

Coronal MR imaging for visualization of wallerian degeneration of the pyramidal tract

A coronal image taken along a straight line between the front edge of the medulla and the deepest point of the interpeduncular cistern clearly displayed wallerian degeneration of the segment of the pyramidal tract between the internal capsule and the pons, the medulla, or the decussation. This visualization was verified in 21 patients with moderate or severe hemiparesis following a stroke episode.     

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.     

Incidental findings on pediatric MR images of the brain

BACKGROUND AND PURPOSE: Previous studies have addressed the prevalence of incidental findings in symptomatic and healthy adult populations. Our study aims to elucidate the prevalence of incidental findings in a healthy pediatric population. METHODS: We retrospectively reviewed 225 conventional brain MR imaging studies obtained during structural and functional brain imaging research in a cohort of neurologically healthy children (100 boys [44%] and 125 girls [56%]) ranging in age from younger than 1 month to 18 years. All MR images were reviewed, and two board-certified neuroradiologists categorized the findings by consensus. RESULTS: Incidental abnormalities were detected in 47 subjects (21%), while 79% of the images were normal. Of the 47 abnormalities detected, 17 (36%) required routine clinical referral; a single lesion (2%) required urgent referral. The occurrence of these findings in the male cohort was twice that of the female cohort; however, the percentage of subjects requiring either routine or urgent referral did not differ by sex (male subjects, 34%; female subjects, 39%). CONCLUSION: Although the frequency of clinically important incidental abnormalities was not high in the sample of children studied, the presence and variety of findings in any pediatric group is particularly important for both the welfare of the subject and for research in which knowledge of the subject's neurologic status is vital to the interpretation of the results. Despite the limitations of the study in terms of the age and ethnic distribution, this work highlights the need for the routine involvement of trained radiologists in these studies to ensure that such incidental findings are detected and that appropriate follow-up is provided.     

Acquired hepatocerebral degeneration: MR and pathologic findings.

Acquired (non-Wilsonian) hepatocerebral degeneration (AHD) is a rare irreversible neurologic syndrome that occurs in patients with chronic liver disease associated with multiple metabolic insults. The pathophysiology and the locations of the cerebral injuries are incompletely understood. We describe a patient with fatal hepatic cirrhosis and AHD in whom MR images showed abnormalities in the brachium pontis bilaterally. Neuropathologic evaluation disclosed multiple regions of subcortical spongiform white matter changes.     

Hypertrophic olivary degeneration: metaanalysis of the temporal evolution of MR findings

BACKGROUND AND PURPOSE: Hypertrophic olivary degeneration (HOD) is usually caused by a lesion in the triangle of Guillain and Mollaret and presents clinically as palatal tremor. Although the imaging features have been well described, the temporal course of hypertrophy and T2 signal increase in the inferior olivary nucleus (ION) has not been fully characterized. Our purpose was to evaluate the time course of MR imaging features of HOD caused by a lesion within the triangle of Guillain and Mollaret. METHODS: The temporal progression of HOD in 45 patients with symptomatic palatal tremor was obtained by extrapolation of combined MR imaging data from six patients treated at our institution and 39 patients reported in the literature. The MR examinations and reports were reviewed for presence of hyperintense signal in the ION on T2-weighted images, hypertrophy of the ION, and an inciting lesion in the triangle of Guillain and Mollaret. The interval between the MR examination and the inciting lesion was determined. RESULTS: Increased olivary signal on T2-weighted images first appeared 1 month after the inciting lesion and persisted for at least 3 to 4 years. Olivary hypertrophy initially developed 6 months after the acute event and resolved by 3 to 4 years. CONCLUSION: Visible changes on MR images in the ION in patients with a lesion in the triangle of Guillain and Mollaret correlate well with the described sequential histopathologic findings.     

Pancreatic disease: findings on state-of-the-art MR images.

Recent technical innovations have made MR imaging a useful technique for imaging the pancreas. The potential impact of MR imaging on the management and outcome of cases can be determined only by controlled prospective comparative studies; however, these cannot be performed adequately until the normal and abnormal appearances of the pancreas on state-of-the-art MR images are understood. This pictorial essay is presented to further this intermediate goal.     

Evaluation of cortical atrophy between progressive supranuclear palsy and corticobasal degeneration by hemispheric surface display of MR images

BACKGROUND AND PURPOSE: Three-dimensional imaging and hemispheric volumetry are useful for the assessment of degenerative cortical atrophy. Our purpose was to determine the features of cortical atrophy in progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) by means of a hemispheric surface display generated with MR images. METHODS: The extent of cortical atrophy was evaluated with automated MR hemispheric surface display and volumetry in 19 patients with PSP and 19 with CBD. RESULTS: Most cortical regions were less atrophic in PSP than in CBD. The parietal lobe, paracentral regions, anterior middle frontal lobe, and posterior inferior frontal lobe were significantly more atrophic in CBD than in PSP, whereas the brainstem was significantly more atrophic in PSP. The mean hemisphere-to-intracranial volume ratio was significantly greater in patients with PSP (74.5%) than in those with CBD (71.4%), whereas the mean brainstem-to-intracranial volume ratio was significantly smaller in PSP (1.4%) than in CBD (1.6%). Asymmetry of hemispheric volume was significantly larger in the CBD group than in the PSP group. CONCLUSION: Hemispheric surface display and volumetry are generally helpful and especially useful for the differentiation of PSP and CBD.     

MR-pathologic comparisons of wallerian degeneration in spinal cord injury.

PURPOSETo describe the MR manifestations and temporal course of wallerian degeneration that occurs above and below a spinal cord injury, and to compare the MR findings with postmortem histopathology.METHODTwenty-four postmortem spinal cords from patients with cervical (n = 14), thoracic (n = 6), and lumbar (n = 4) cord injuries were studied with axial T1- and T2-weighted spin-echo MR imaging. Injury-to-death intervals varied from 8 days to 23 years. The images were examined for alteration of signal above and below the injury site. Histologic studies of these cords with axon, myelin, and connective tissue stains were performed at levels equivalent to the MR sections. Immunohistochemical analysis using antibodies to glial fibrillary acetic protein was also performed on 19 cords. Pathologic-imaging comparisons were made.RESULTSMR images showed increased signal intensity in the dorsal columns above the injury level and in the lateral corticospinal tracts below the injury level in all cases in which cord injury had occurred 7 or more weeks before death. In early postinjury survival times (8 days and 12 days) MR findings were normal; histologically there was early wallerian degeneration in only the dorsal columns at 8 days and in both the lateral and dorsal columns at 12 days. MR showed wallerian degeneration in all cases examined at 7 weeks after injury and thereafter.CONCLUSIONSWallerian degeneration was demonstrated by histology and MR in all specimens in which the injury-to-death interval was greater than 7 weeks. Recognition of wallerian degeneration on MR allows complete analysis of the injury, explains abnormal MR signals at sites remote from the epicenter of the injury, and may be useful in the future in the timing and planning of therapeutic interventions.     

Foci of decreased signal on T2-weighted MR images in leiomyosarcomas of soft tissue: correlation between MR and histological findings

OBJECTIVE: Leiomyosarcomas are rare soft tissue sarcomas with varying MR signal characteristics and histologic pictures. The purpose of this study was to investigate the histological features of foci, which showed decreased signal on T2-weighted images in leiomyosarcomas of soft tissue. MATERIAL AND METHODS: We reviewed the MR images of six histologically proved cases of leiomyosarcomas of soft tissue and correlated the foci, which showed decreased signal on T2-weighted images with the histologic findings. RESULT: Microscopic examination revealed that these foci were composed of hyalinization of neoplastic tissue, internal septations, deposition of hemosiderin, or corresponded to metaplastic bone. CONCLUSION: The authors explain that the foci of decreased signal on T2-weighted MR images correspond to tissue components of the lesion, particularly fibrous tissue, hemosiderin and metaplastic bone. So, the suggestion is that leiomyosarcoma should be considered in the differential diagnosis of soft-tissue tumors that show foci of decreased signal on T2-weighted MR images.     

The effects of wallerian degeneration of the optic radiations demonstrated by MRI

Summary The effects of wallerian degeneration can be demonstrated by MRI as abnormal signal along the course of the degenerate fibres; they have previously been reported in the corticospinal tract. We report two cases of wallerian degeneration of the right optic radiations due to lesions of the right lateral geniculate body. The anatomy and the MRI visibility of the normal optic radiations are briefly discussed.     

Correlation between high field MR images and histopathological findings of rat transplanted cancer immediately after partial microwave coagulation

PURPOSE: To investigate the immediate effects of microwave coagulation on rat tumors in various magnetic resonance (MR) images at high magnetic field strength using histopathological examinations as reference. MATERIALS AND METHODS: Tumors implanted in rat femurs were partially thermocoagulated by microwave. Immediately after, T1- and T2-weighted images, diffusion-weighted images (DWIs), and contrast-enhanced T1 weighted images (CE-T1WIs) were acquired with a 7-tesla MR scanner. After measurements, tumors were examined histopathologically with hematoxylin-eosin (HE) staining and histochemically for acid phosphatase activity. RESULTS: Without contrast, boundaries of coagulated areas were unclear on MR images, including apparent diffusion coefficient (ADC) maps. CE-T1WIs clearly showed immediate contrast enhancement of untreated areas of tumor, and the area of enhancement gradually enlarged in 5 min. Quantitative analyses were conducted by classifying tumor areas by contrast enhancement results. Signal intensities of the areas in the MR images showed no significant differences, but at the periphery, ADC values were significantly higher in areas with delayed enhancement than those with immediate enhancement. Compared with histopathological findings, with microwave thermocoagulation, increased ADC value seemed to derive from collection of extracellular fluid in the outer zone, where acid phosphatase activity was attenuated. CONCLUSION: ADC values in the areas with delayed enhancement of CE-T1WIs were higher than those in non-affected areas, but MR images could not show areas of coagulation within tumors. Clear detection of the boundaries of coagulated areas required contrast enhancement, even at magnetic field strength of 7T.     

Perilesional hyperintense rim of malignant hepatic tumors on ferumoxide-enhanced T1-weighted gradient-echo MR images: correlation between MR imaging and histopathologic findings

PURPOSE: To correlate the perilesional hyperintense rim of malignant hepatic tumors seen on ferumoxide-enhanced T1-weighted gradient-echo (GE) MR images with histopathologic findings. MATERIALS AND METHODS: In 13 tumors in 12 patients, T1-weighted GE images (TE of 1.4 msec, flip angle of 90 degrees) obtained after IV administration of ferumoxide were evaluated. MR imaging was initiated within one hour of the completion of ferumoxide administration. Surgical resection for tumors was performed within an interval of two weeks of the MR imaging. Resected specimens were histopathologically examined for peritumoral sinusoidal congestion, desmoplastic reaction, compressed hepatic parenchyma, lymphocytic infiltration, and vascular proliferation. RESULTS: In twelve tumors (92%), prominently (N = 2), moderately (N = 5), and mildly to minimally (N = 5), a perilesional hyperintense rim was observed. Among histopathologic findings, the degree of peritumoral sinusoidal congestion correlated (R =.75, P <.04) with the degree of perilesional hyperintense rim. The thickness of the perilesional hyperintense rim showed a moderate positive correlation (R =.65, P <.02) with the thickness of peritumoral area with sinusoidal congestion. CONCLUSION: Perilesional hyperintense rim of malignant hepatic tumors on ferumoxide-enhanced T1-weighted GE images may correlate with sinusoidal congestion surrounding malignant hepatic tumors.     

缺血性脑卒中华勒变性的磁共振波谱研究

目的 应用磁共振波谱成像(MRS)了解缺血性脑卒中梗死灶变化及大脑脚华勒变性的发生、发展.方法 选取缺血性脑卒中患者与健康对照各10例,行常规轴位T2WI、FLAIR及MRS扫描.随访8周,测量卒中灶及患侧大脑脚的MRS值,观察并分析数值的变化.结果 (1)卒中灶NAA下降,Cho上升;(2)第1周2组梗死区NAA/Cr无统计学差异;大脑脚MRS无差异.(3)第8周2组梗死区NAA/Cr、NAA/Cho差异有统计学意义;卒中组大脑脚NAA/Cho低于健康组(P=0.000).结论 MRS能从分子水平早期发现缺血性脑卒中患者梗死灶远端脑组织继发性改变.     

Dyke Award paper. MR of wallerian degeneration in the feline visual system: characterization by magnetization transfer rate with histopathologic correlation.

PURPOSETo examine the utility of measuring magnetization transfer ratio for for delineating the dynamic changes of wallerian degeneration which occur after controlled injury in a feline model in which anatomic pathways are well understood.METHODSUsing standard neurosurgical techniques, discrete lesions were made to ablate the visual cortex. Gradient imaging was performed serially at 1.5 T, with and without a saturation pulse to create a magnetization transfer effect. At varying intervals, the animals were killed for histologic analysis.RESULTSWithin the first 2 weeks there is a statistically significant increase in magnetization transfer ratio relative to the control hemisphere within the white matter connections between the lateral geniculate nucleus and the visual cortex at a time when no effects are visually detectable on spin-echo images. Between 16 and 28 days, this reverses to a decrease in magnetization transfer ratio in both the lateral geniculate nucleus itself and the adjacent superolateral white matter. More remote white matter tracts remained stable, without significant change.CONCLUSIONSMagnetization transfer ratio seems to be more sensitive for early detection of degeneration than conventional spin-echo imaging. Moreover, temporal changes in magnetization transfer ratio seem to correspond well with known histologic phases of wallerian degeneration.     

Shy—Drager综合征与纹状体黑质变性MRI—病理对照研究

目的：探讨Ｓｈｙ－Ｄｒａｇｅｒ综合征（ＳＤＳ）、纹状体黑质变性（ＳＮＤ）ＭＲＩ异常信号与病理改变的关系。材料与方法：分别对ＳＤＳ、ＳＮＤ各１例脑标本进行ＭＲＩ扫描与病理对照研究。使用自旋回波（ＳＥ）序列扫描，对照ＭＲＩ图像所显示的异常信号行标本大体及镜下观察。结果：ＳＤＳＭＲＩ显示壳核对称性短Ｔ２低信号，病理改变为神经细胞数量减少，铁元素过度沉积；ＳＮＤＭＲＩ显示双侧壳核等Ｔ１、长Ｔ２信号，病理证实为神经细胞数量减少并坏死，胶质增生、毛细血管增多、脂褐素增多。结论：ＭＲＩ壳核异常信号的显示对生前诊断ＳＤＳ与ＳＮＤ具有重要参考价值     

Rapid spongiform degeneration of the cerebrum and cerebellum in Creutzfeldt-Jakob encephalitis: serial MR findings.

We report the cerebral MR imaging findings in a patient with pathologically proved Creutzfeldt-Jakob disease in whom predominant gray and white matter degeneration was seen within 1 year of symptom onset. The initial MR signal abnormalities in the basal ganglia were subtle. A follow-up MR examination revealed diffuse cerebral and cerebellar atrophy and demyelination.     

Small-bowel disease: comparison of MR enteroclysis images with conventional enteroclysis and surgical findings

PURPOSE: To investigate if magnetic resonance (MR) enteroclysis can be performed routinely and to compare MR enteroclysis findings with those of conventional enteroclysis or surgery. MATERIALS AND METHODS: MR enteroclysis was prospectively performed in 30 patients with symptoms of inflammatory bowel disease or small-bowel obstruction (SBO). A methylcellulose-water solution was used to distend the small bowel. To monitor dynamic changes in the small bowel, a single-shot fast spin-echo T2-weighted sequence was applied. For morphologic assessment, breath-hold T2-weighted fast spin-echo and coronal T1-weighted gradient-recalled-echo MR images were obtained without and with gadolinium enhancement. Image quality and degree of small-bowel distention were graded. MR imaging findings and degree of SBO were compared with findings at conventional enteroclysis (n = 25) or surgery (n = 5). RESULTS: MR enteroclysis was well tolerated and provided adequate image quality and sufficient small-bowel distention. SBO grade based on MR enteroclysis images (n = 10) was identical to that based on conventional enteroclysis images (n = 6) or surgical findings (n = 4). There was exact agreement between MR enteroclysis and retrospective findings in all five patients who underwent surgery, and MR findings were identical to those at enteroclysis in 18 patients, superior in six patients, and inferior in one patient. CONCLUSION: MR enteroclysis can be performed routinely with adequate image quality and sufficient small-bowel distention. The functional information provided by MR enteroclysis is identical to that provided at conventional enteroclysis.