三叉神经节和Meckel''s腔原发性肿瘤的MRI表现

目的 研究三叉神经节和Meckel’s腔原发肿瘤的MRI表现。方法 对14例经病理证实的三叉神经节和Meckel’s腔原发肿瘤患包括4例三叉神经鞘瘤，5例脑膜瘤，1例脂肪瘤，以及4例表皮样囊肿的MRI表现进行了分析。结果 三叉神经鞘瘤在T1WI上呈均匀低信号，在T2WI上呈高信号。5例脑膜瘤中的3例在T1WI和T2WI上与周围脑组织信号一致，1例在T1WI上呈低信号，在T2WI上呈高信号，另1例在CT图像上有丰富的钙质沉着而在T1WI和T2WI上均呈低信号。脂肪瘤信号均匀且与眶内和皮下脂肪信号一致。4例表皮样囊肿的2例在T1WI和T2WI上呈非常高的信号，另外2例呈匍匐性生长并且占位效应较轻。肿瘤侵犯三叉神经能很好的显示其范围。结论 发生自三叉神经节和Meckel’s腔的不同原发肿瘤具有各自的信号特征，可通过MR成像予以鉴别。     

胰腺MRI、MRS和MRCP检查与正常表现

MR检查已成为临床上评价胰腺疾病的常用手段.了解不同MR脉冲序列上正常胰腺的影像表现是合理应用扫描序列和识别病变的前提.介绍了胰腺MRI、磁共振波谱和磁共振胆胰管成像检查技术,描述了正常胰腺影像解剖以及不同脉冲序列上胰腺MRI信号变化情况.     

MR imaging and MR angiography of persistent trigeminal artery and its variant

Six patients with persistent trigeminal artery (PTA) and one patient with its variant (PTAV) were studied using a 1.0-T magnetic resonance unit. With both magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), four of the six PTAs were detected as abnormal connecting arteries between the cavernous internal carotids and the basilar arteries. The remaining two PTAs and one PTAV were not detected using MRI, but were imaged by MRA. It was concluded that relatively large PTAs can be detected using MRI, but small PTAs and PTAVs may be missed using MRI.     

MR imaging of extracranial nerve sheath tumors.

We retrospectively reviewed MR images of 32 histologically proven extracranial nerve sheath tumors (NSTs). There were 23 benign (10 neurofibromas, 13 schwannomas) and 9 malignant NSTs. On T1-weighted images (T1WIs) tumors were isointense or slightly hyperintense to muscle. On T2-weighted images (T2WIs) (11 lesions) and enhanced T1WIs (1 intraspinal lesion), a target pattern with peripheral hyperintense rim and central low intensity was seen in 12 of 23 (52%) benign NSTs (5 of 10 neurofibromas and 7 of 13 schwannomas). This pattern corresponded histologically to peripheral myxomatous tissue and central fibrocollagenous tissue. The pattern was absent in lesions with cystic, hemorrhagic, or necrotic degeneration. These tumors were hyperintense and variably inhomogenous on T2WIs. Malignant NSTs were hyperintense and variably inhomogenous on T2WIs and mimicked benign variably inhomogeneous lesions unless involvement of contiguous structures was visualized. A target pattern was not visible in malignant lesions. Magnetic resonance imaging cannot distinguish schwannomas from neurofibromas, and benign tumors may mimic malignant NSTs when cystic, hemorrhagic, and necrotic degeneration is present. A target pattern may be visualized in some benign NSTs, and evaluation of this sign with assessment of location and growth along nerves may help to avoid confusion with other lesions.     

Optic nerve sheath meningiomas. Role of MR imaging

Optic nerve meningiomas usually are seen in middle-aged and elderly women, and present as a slowly progressing axial proptosis and loss of vision. CT and MR imaging are the most valuable diagnostic tools to evaluate these tumors. This article reviews the MR imaging and CT characteristics of optic nerve sheath meningiomas and discusses features that may distinguish optic nerve sheath meningiomas from simulating lesions.     

Suprascapular nerve entrapment: evaluation with MR imaging.

Entrapment of the suprascapular nerve is frequently overlooked in the differential diagnosis of shoulder pain. The diagnosis is typically not considered until patients develop severe weakness secondary to atrophy of the spinatus (spinous) musculature that the nerve supplies. Twenty-seven masses were identified adjacent to the suprascapular nerve on magnetic resonance (MR) images of the shoulder; there were 21 ganglion cysts, two synovial sarcomas, one Ewing sarcoma, one chondrosarcoma, one metastatic renal cell carcinoma, and one hematoma associated with a fracture. Atrophy of both the supraspinatus and infraspinatus muscles was seen in association with anteriorly located masses and proximal entrapment of the nerve in 11 cases (40%); isolated atrophy of the infraspinatus muscle was seen in association with posteriorly located masses and distal entrapment of the nerve in nine cases (33%). MR imaging may facilitate the diagnosis of suprascapular nerve entrapment in patients with shoulder pain of unclear origin when perineural masses and atrophy of the spinatus musculature are present.     

1.5T和3.0T磁共振正常节后臂丛神经IDEAL成像质量的评估

节后臂丛神经在空间走行上既不共线也不共面且毗邻关系复杂,很多成像设备无法满足临床的影像要求。磁共振神经成像(magnetic resonance neurography,MRN)被报道以来已成为臂丛神经病变检查的首选方法[1],作为外科手术的引导工具,更有学者把 MRN 视为金标准[2]。本研究以 T2快速自旋回波序列加迭代最小二乘估算法水脂分离技术(iterative decomposition of water fat with echo asymmetry and least-squares estimation,IDEAL)扫描节后臂丛神经,从影像技术的角度探讨同机型不同场强磁共振正常节后臂丛神经成像质量的差异。     

Facial nerve enhancement in MR imaging

The significance of facial nerve enhancement after IV gadolinium administration has not been determined. We evaluated the MR appearance of facial nerves (nonenhanced and enhanced) in patients without and with masses involving the temporal bone, internal auditory canal, or cerebellopontine angle. In patients without such masses, no facial nerve enhancement was seen. In the other group, four of 11 patients showed facial nerve enhancement and geniculate ganglion masses. Three of these four patients had neurofibromatosis; one had surgical verification of a facial nerve neurofibroma. Enhanced MR facilitates identification of abnormal facial nerves.     

Correlation of MR imaging and histologic findings in mouse melanoma.

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 microns thick, with an in-plane resolution of 195 microns. The distribution of melanin within the histologic slices correlated well with the high-signal-intensity regions on the T1-weighted images (T1WIs), while these regions had low signal intensity on the T2-weighted images (T2WIs), providing evidence that melanin or melanin-associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton-density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton-density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin-rich, viable-melanoma, and necrotic regions on MR images.     

Facial nerve neuromas: MR imaging

Summary Four cases of facial nerve neuroma were evaluated by computed tomographic (CT) scan and magnetic resonance imaging (MRI). The extension of the tumor in the petrous bone or the parotid gland was well defined by MRI in all cases. CT scan was useful to demonstrate bone erosions and the relation of the tumor to inner ear structures. In cases of progressive facial palsy, CT and MRI should be combined to detect a facial neuroma and to plan the surgical approach for tumor removal and nerve grafting.     

Persistent primitive trigeminal artery aneurysm evaluated by MR imaging and angiography

The primitive trigeminal artery is the most common of the persistent carotid-basilar anastomoses with an angiographic incidence of 0.6%. Fifteen cases of aneurysms of a persistent primitive trigeminal artery have been reported in the literature. A 16th patient is presented in whom an incidental trigeminal artery aneurysm and a thrombosed aneurysm of the vertebrobasilar system are evaluated by magnetic resonance imaging and angiography.     

MR imaging of primary trochlear nerve neoplasms

We present the clinical, anatomic, and MR imaging findings in six patients with seven primary trochlear nerve neoplasms, as well as the MR and clinical criteria that serve to establish the diagnosis of these rare cranial nerve neoplasms. Three patients had a history of neurofibromatosis and five patients had clinical evidence of a trochlear nerve palsy. Six of seven neoplasms produced localized, fusiform enlargement of the proximal cisternal segments of the trochlear nerves. The lesions that were visible on noncontrast MR scans (T1-, T2-, and proton density-weighted) had signal intensities that were virtually identical to normal brain parenchyma. All lesions showed intense, homogeneous enhancement on contrast-enhanced scans. Contrast-enhanced imaging was necessary for the detection of five of seven lesions and greatly increased the value of the MR study in all six patients.     

MR imaging evaluation of suprascapular nerve entrapment

The aim of this study was to assess the significance of muscular edema, atrophy, and fatty changes in the diagnosis of suprascapular nerve entrapment (SSNE), and to confirm muscular edema as the most significant sign of neuropathy. A retrospective study of 18 patients with suprascapular nerve entrapment was performed. All patients underwent electromyographic studies and MR imaging with a 1.5-T Echo Speed system (General Electric, Milwaukee, Wis.). The diagnosis of muscle edema was reached when muscles presented a high signal on T2-weighted fast spin-echo (SE) fat-suppressed images. Muscular trophicity and fatty changes were analyzed on a sagittal oblique cut using SE T1-weighted images. Intra- and inter-observer reproducibility using kappa test, sensitivity, and specificity were analyzed, together with negative and positive predictive value of each criterion. The topographic diagnosis was correct as edema affected the infraspinatus muscle alone when the suprascapular nerve was entrapped at the spinoglenoid notch. Both the supraspinatus and infraspinatus muscles were affected when nerve was compressed at the suprascapular notch. Sensitivity and specificity of muscular edema were, respectively, 94.5 and 100%. Muscular atrophy sensitivity and specificity were 81 and 80%, respectively. Fatty changes sensitivity and specificity were 25 and 96%, respectively. Muscular edema seems to be a more sensitive sign of SSNE than muscle atrophy and fatty changes when compared with EMG results. Magnetic resonance imaging can reach a positive, topographic, and etiologic diagnosis of SSNE.     

CT and MR imaging of the normal and pathologic conditions of the facial nerve.

Computed tomography (CT) and magnetic resonance imaging (MRI) are well established imaging modalities to examine the facial nerve as well as the course of the facial nerve itself. High spatial resolution is guaranteed not only in the x- and y-axis, but also in the z-axis using multislice spiral CT. With this technique, reformatted multiplanar images in oblique planes, avoiding additional examinations in the coronal plane, facilitate the delineation of the facial nerve canal. This is beneficial in patients with temporal bone trauma, malformation or osseous changes. MR has a superior soft-tissue contrast to CT that enables imaging of the facial nerve itself. Therefore the normal facial nerve as well as pathologic changes of the facial nerve is readily visualized from the brain stem to the parotid gland. This review article presents anatomy, pathology and imaging strategies in the diagnostics of the facial nerve.     

单侧大脑中动脉狭窄程度与磁共振血流灌注相关性研究

目的:探讨大脑中动脉(MCA)狭窄程度与脑磁共振灌注加权成像(PWI)的相关性.方法:30例短暂性脑缺血发作(TIA)患者行高分辨力MRI检查并判断单侧MCA狭窄程度,同时行磁共振PWI检查,并对MCA不同狭窄状态下得出的患侧和镜像侧灌注参数,包括相对脑血容量(rCBV)、相对脑血流量(rBCF)、相对平均通过时间(rMTT)、相对达峰时间(rTTP)进行定量分析.结果:30例患者中,高分辨力MRI均可显示不同程度MCA狭窄,灌注均出现异常,患侧灌注参数rCBV、rCBF、rMTT、rTTP与镜像侧比较,差异均有统计学意义(P＜0.05).MCA狭窄率与rMTT延长百分率之间呈正相关性(r=0.45,P＜0.05).结论:高分辨力MRI对MCA狭窄程度的评估与PWI灌注参数之间存在正相关性,MCA狭窄程度与PWI相结合对于评价脑组织供血有一定的指导意义.