Imaging of cerebellopontine angle lesions: an update. Part 2: intra-axial lesions,skull base lesions that may invade the CPA region,and non-enhancing extra-axial lesions

Computed tomography (CT) and magnetic resonance (MR) imaging reliably demonstrate typical features of vestibular schwannomas or meningiomas in the vast majority of mass lesions responsible for cerebellopontine angle (CPA) syndrome. However, a large variety of unusual lesions can also be encountered in the CPA. Covering the entire spectrum of lesions potentially found in the CPA, these articles explain the pertinent neuroimaging features that radiologists need to know to make clinically relevant diagnoses in these cases, including data from diffusion- and perfusion-weighted imaging or MR spectroscopy, when available. A diagnostic algorithm based on the lesion’s site of origin, shape and margins, density, signal intensity and contrast material uptake is also proposed. Non-enhancing extra-axial CPA masses are cystic (epidermoid cyst, arachnoid cyst, neurenteric cyst) or contain fat (dermoid cyst, lipoma). Tumours can also extend into the CPA by extension from the skull base (paraganglioma, chondromatous tumours, chordoma, cholesterol granuloma, endolymphatic sac tumour). Finally, brain stem or ventricular tumours can present with a significant exophytic component in the CPA that may be difficult to differentiate from an extra-axial lesion (lymphoma, hemangioblastoma, choroid plexus papilloma, ependymoma, glioma, medulloblastoma, dysembryoplastic neuroepithelial tumour).     

Differentiation of cerebellopontine angle neuromas and meningiomas with MR imaging

Postcontrast CT of the temporal bone is the neuroradiological study of choice for investigation of cerebellopontine angle (CPA) and internal auditory canal (IAC) lesions. Nonenhancing or small lesions may need CT combined with air or metrizamide cisternography for their detection. Magnetic resonance (MR) imaging has shown interesting capabilities as a noninvasive study for the visualization of the IAC, the neural bundle entering the canal, the brain stem, and cerebellum. In the present series of 24 cases, MR imaging detected the lesion in all 11 verified tumors. We feel that MR can replace invasive air and metrizamide cisternography in the diagnosis of CPA lesions and can help in the differentiation between acoustic neuromas and meningiomas.     

Imaging of cerebellopontine angle lesions: an update. Part 1: enhancing extra-axial lesions

Computed tomography (CT) and magnetic resonance (MR) imaging reliably demonstrate typical features of vestibular schwannomas or meningiomas in the vast majority of mass lesions in the cerebellopontine angle (CPA). However, a large variety of unusual lesions can also be encountered in the CPA. Covering the entire spectrum of lesions potentially found in the CPA, these articles explain the pertinent neuroimaging features that radiologists need to know to make clinically relevant diagnoses in these cases, including data from diffusion and perfusion-weighted imaging or MR spectroscopy, when available. A diagnostic algorithm based on the lesion’s site of origin, shape and margins, density, signal intensity and contrast material uptake is also proposed. Part 1 describes the different enhancing extra-axial CPA masses primarily arising from the cerebellopontine cistern and its contents, including vestibular and non-vestibular schwannomas, meningioma, metastasis, aneurysm, tuberculosis and other miscellaneous meningeal lesions.     

桥小脑角区病变的MRI表现

目的探讨桥小脑角（cerebellopontineangle,CPA）区占位性病变在磁共振检查中的影像表现。方法分析83例行MRI平扫＋增强检查,且经手术病理证实,具有完整临床资料的CPA占位性病变的MRI表现,重点观察病灶的大小、形态、边缘轮廓、瘤周水肿、周围结构的改变、平扫及增强后的信号强度。结果本组83例CPA病变中,听神经瘤50例,脑膜瘤13例,表皮样囊肿13例,三又神经瘤4例,蛛网膜囊肿1例,星形细胞瘤1例,室管膜瘤1例。肿瘤位于左侧CPA区38例,右侧CPA区45例。术前定位准确率为98．8％,定性准确率为95．2％。结论MRI检查是检查桥小脑角区占位性病变的首选方法,对该区病变的诊断和鉴别诊断有重要价值。     

CT和MRI对颅内表皮样囊肿诊断价值的评价

目的：评估CT和MRI对颅内表皮样囊肿的诊断价值，分析误诊原因，提高诊断水平。方法：44例经手术和病理证实的颅内表皮样囊肿，术前全部行常规MRI检查，其中19例行Gd-DTPA增强MRI检查；17例作CT平扫，其中12例作静脉注射增强CT检查。结果：颅内表皮样囊肿多位于桥小脑角池，本组病例中占34．9％(15／4例)；肿瘤多呈不规则形态，占70．45％(31／44例)；CT平扫多呈均匀低密度，占70．59％(12/17例)，造影后多无强化，占91．71％(11／12例)；MRT1加权像上多呈均匀低信号，但略高于脑脊液，T2加权像上多呈均匀高信号，占61．36％(27／44例)，Gd-DTPA增强后多无强化，占84．21％(16／19例)。肿瘤周围的脑组织均无水肿，占100％，肿瘤较大时可以挤压、推移周围脑组织或脑室结构，引起比较明显的占位效应，占70．45％(31／44例)；肿瘤较大时，很少引起阻塞性脑积水。结论：颅内表皮样囊肿在CT和MRI像上有特征性表现，MRI无论在定位和定性诊断上优于CT，Gd-DTPA的应用有助于颅内囊性占位的诊断与鉴别诊断。     

Orbital tumors in children: CT and MR imaging features

The purpose of the article is to review the CT and MR imaging features of orbital tumors in children. Tumors in children are usually different than those in adults. Clinical symptoms are usually non-specific. Clinical examination combined with US may be sufficient for diagnosis and follow-up of benign and superficial lesions. CT and/or MRI are needed for deep or malignant lesions. CT is valuable for osseous and/or calcified lesions. MR is advantageous because of its superior spatial resolution and non-ionizing nature. Malignant tumors correspond to about 20% of lesions and include primary tumors (retinoblastoma, rhabdomyosarcoma) and metastases. Benign pathology is more frequent (80%) with dermoid cyst corresponding to about 50% of orbital masses.     

Differential diagnosis of dumbbell lesions associated with spinal neural foraminal widening: imaging features

Computed tomography (CT) and magnetic resonance imaging (MRI) reliably demonstrate typical features of schwannomas or neurofibromas in the vast majority of dumbbell lesions responsible for neural foraminal widening. However, a large variety of unusual lesions which are causes of neural foraminal widening can also be encountered in the spinal neural foramen. Radiologic findings can be helpful in differential diagnosis of lesions of spinal neural foramen including neoplastic lesions such as benign/malign peripheral nerve sheath tumors (PNSTs), solitary bone plasmacytoma (SBP), chondroid chordoma, superior sulcus tumor, metastasis and non-neoplastic lesions such as infectious process (tuberculosis, hydatid cyst), aneurysmal bone cyst (ABC), synovial cyst, traumatic pseudomeningocele, arachnoid cyst, vertebral artery tortuosity. In this article, we discuss CT and MRI findings of dumbbell lesions which are causes of neural foraminal widening.     

Benign bone tumors and tumor-like lesions: value of cross-sectional imaging

This article reviews the role of CT and MR imaging in the diagnosis of benign bone tumors and tumor-like lesions of bone with with regard to differential diagnosis, the assessment of tumor-related complications, and the detection of postoperative recurrence. Indications for cross-sectional imaging of specific lesions, including osteoid osteoma, osteoblastoma, enchondroma, osteochondroma, intraosseous lipoma, hemangioma, giant cell tumor, aneurysmal bone cyst, simple bone cyst, and eosinophilic granuloma, are discussed, and advantages and disadvantages of the different imaging modalities are illustrated on the basis of pathologically confirmed cases.     

Magnetic resonance findings in 92 acoustic neuromas.

A retrospective analysis of the MR findings in 92 cases of acoustic neuromas is presented. The method of examination included in all cases intravenous injection of Gadolinium (Gd-DTPA or DOTA) with realization of sections in the axial and coronal planes. In 21 cases native MR studies were performed in the axial plane, before Gadolinium injection, with T1WI (n = 21), and T2WI (n = 6) images. Tumors were strictly intracanalar in 19 cases (20.7%), only localized in the cerebellopontine angle (CPA) in 5 cases (5.4%), and in 68 cases (73.9%) the tumors had intra- and extracanalar components. In this last group of lesions, 63.2% completely filled the internal auditory canal (IAC), and 36.8% occupied the internal portion of the IAC. In most cases (85.3%) the mean diameter of the CPA component was less than or equal to 2.5 cm. Lesions were more frequently homogeneous (58.8%) after Gd i.v.-enhancement. Heterogeneity was noted mainly in large lesions (greater than 2.5 cm: 100%). In all cases but one, the tumors were round, or oval-shaped, well-delineated, and did not present significant contact with the petrous bone. In 80.9% of CPA lesions, the center of the tumor was posteriorly excentered in relation to the internal auditory canal, whereas it was centered in 16.2% of cases. Widening of the IAC was observed in 51.1% of cases. In 45.2% of tumors of the CPA, smoothing of the posterior edge of the porus was visible.     

Congenital cholesteatoma of the temporal bone: MR findings and comparison with CT.

PURPOSETo describe the MR findings of temporal bone congenital cholesteatoma and MR usefulness in preoperative diagnosis and follow-up, in comparison with CT.METHODSSeven patients underwent CT and MR studies for facial palsy (n = 3), deafness (n = 3), vertigo (n = 1), tinnitus (n = 1), and otalgia (n = 1). Three patients had for congenital cholesteatoma previously undergone surgery. One of them was free of symptoms and referred for follow-up. Final diagnosis was obtained from surgical data in all the cases but one.RESULTSCongenital cholesteatoma signal intensity was low or intermediate on T1-weighted images and high on T2-weighted images in all the cases. MR was useful in diagnosis in six cases, helping to differentiate congenital cholesteatoma from other nonenhancing tumors. When temporal bone wall erosion was observed with CT (n = 6), MR ruled out intracranial extension in five cases; in one case, MR found an associated epidermoid cyst of the cerebellopontine angle not identified with CT. However, CT assessed relationships with labyrinthine structures more easily.CONCLUSIONMR and CT are complementary in initial diagnosis and follow-up.     

良性泪腺混合瘤CT、MR诊断价值

目的:探讨良性泪腺混合瘤CT和MR诊断价值。方法:对12例经手术及病理学证实的良性泪腺混合瘤患者进行回顾性分析,观察其CT及MR表现的特点。结果:12例患者中,类圆形8例,椭圆形4例。肿瘤位于眼眶上、外方,眼球受压向下内移位。肿瘤边界清晰,周围泪腺窝骨质膨胀变薄。CT表现为肿块与脑组织密度相似,等密度均匀8例,密度不均匀4例。MR表现为T1WI呈低信号,T2WI及脂肪抑制相呈高信号。增强扫描肿瘤明显强化8例,4例轻中度强化。结论:CT、MR可清晰地显示泪腺混合瘤的形态、大小、密度等,具有一定特征性,为该病诊断和鉴别诊断提供了可靠的诊断依据。     

泪腺恶性上皮性肿瘤的CT、MRI诊断

目的 总结泪腺恶性上皮性肿瘤的CT和MRI表现.方法 回顾性分析16例经病理学证实的泪腺恶性上皮性肿瘤CT和MRI影像资料.结果 16例泪腺恶性上皮性肿瘤,15例位于泪腺窝,1例位于眶缘前.5例呈类圆形,11例呈不规则形(其中9例后缘变尖,5例沿眶壁前后方向或上下方向生长),8例泪腺窝骨质受压,6例眶壁骨质破坏,1例眶壁骨质硬化;3例侵犯颅内;1例见额部皮下转移灶;2例CT可见钙化.MRI示肿瘤呈等、长T_1长T2信号,增强扫描可见强化.结论 CT及MRI可显示泪腺恶性上皮性肿瘤的特征,有助于泪腺恶性上皮性肿瘤的诊断及鉴别诊断.     

桥小脑角区占位病变的MRI诊断及鉴别诊断

目的:探讨桥小脑角区(CPA)占位病变MR诊断及鉴别诊断价值。方法:搜集收治经手术和病理证实的桥小脑角区肿瘤患者91例,回顾性分析其MR表现。结果:听神经瘤64例,脑膜瘤17例,三叉神经瘤5例,表皮样囊肿3例,颈静脉球瘤1例,血管母细胞瘤1例。结论:MRI能较好地对CPA区占位病变作出诊断及鉴别诊断。     

Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients

BACKGROUND AND PURPOSE: Intracranial solitary fibrous tumors (ISFTs) are rare mesenchymal neoplasms originating in the meninges. The aim of this study was to describe the CT, MR imaging, and angiographic features of the solitary fibrous tumor and to identify imaging characteristics. MATERIALS AND METHODS: We retrospectively reviewed CT, MR, and angiographic findings in 6 cases of ISFT. We evaluated the size, shape, and location of the tumor; the internal content and margin of the lesion; the pattern of enhancement; and the change of the adjacent structures. Density on noncontrast CT scans, signal intensity on MR images, and angiographic features were also documented. RESULTS: Each lesion appeared as a discrete extra-axial mass (size, 3-7 cm; mean, 5 cm). Five lesions were entirely solid, and 1 had peritumoral cyst. All 5 of the noncontrast CT scans showed hyperattenuated masses, and the tumors exhibited marked heterogeneous enhancement. No lesion contained calcification, and 2 cases showed bone invasions. On the MR images, 4 lesions showed mixed signal intensity on T2-weighted imaging. All of the lesions revealed marked heterogeneous enhancement. All of the tumors had thickening of the meninges adjacent to the tumor. Angiography showed delayed tumor blushing in all, and 3 of them had dysplastic dilation of the tumor vessels. CONCLUSION: Although there are no pathognomonic imaging findings, some imaging features, such as the "black-and-white mixed" pattern on T2-weighted images and marked heterogeneous enhancement, might be helpful in the diagnosis of intracranial solitary fibrous tumor.     

Inflammatory myofibroblastic tumor of the temporal bone

Inflammatory myofibroblastic tumors include a diverse group of lesions characterized by inflammatory cell infiltration and variable fibrotic responses. Occurrence in the temporal bone is unusual. We present CT and MR imaging findings of an inflammatory myofibroblastic tumor of the temporal bone in a 26-year-old patient with repeated paroxystic episodes of rotatory vertigo that occurred over a few days. CT and MR imaging revealed a homogeneously enhancing soft-tissue mass of the right mastoid with bone erosion of the tegmen and extensive dural thickening. The mass resembled a malignant tumor, and the patient underwent an extended mastoidectomy through a retroauricular approach. Microscopic examination showed myofibroblastic spindle cells with mixed inflammatory infiltrate, and the pathologic diagnosis was inflammatory myofibroblastic tumor.     

髂骨原发囊样骨肿瘤及瘤样病变的影像学诊断

目的:分析髂骨囊样骨肿瘤及肿瘤样病变的影像学表现。方法:回顾性分析经穿刺或/和手术病理证实的46例髂骨囊样骨肿瘤及肿瘤样病变影像学表现。46例全部行X线片检查,38例行CT检查,20例行MRI检查(增强16例)。结果:46例中骨肿瘤29例,其中良性肿瘤12例(骨巨细胞瘤4例,内生软骨瘤、软骨母细胞瘤各2例,血管瘤、骨母细胞瘤、骨样骨瘤、软骨黏液样纤维瘤各1例),恶性肿瘤17例(恶性巨细胞瘤、骨恶性纤维组织细胞瘤各1例,软骨肉瘤、淋巴瘤各4例,骨肉瘤7例),肿瘤样病变17例(单纯性骨囊肿1例,邻关节骨囊肿、动脉瘤样骨囊肿、嗜酸性肉芽肿各2例,骨纤维异常增生症10例)。发病部位为髂翼39例,髋臼7例。病变主要表现为髂骨囊样骨质破坏,呈膨胀性改变30例,硬化环形成24例,病变内见钙化灶14例,软组织肿块20例。结论:常见的髂骨囊样骨肿瘤和肿瘤样病变一般都具有某些特征性的CT表现,必要时综合X线、MRI表现,可提高定性诊断符合率。     

MR imaging of epidermoids at the cerebellopontine angle.

The most common location of intracranial epidermoid is the cerebellopontine angle (CPA). The present study compared the visibility of epidermoid at the CPA in various pulse sequences. Seven patients with epidermoid at the CPA underwent conventional MR imaging (T(1)-, T(2)- and proton density-weighted imaging) as well as diffusion-weighted echo-planar imaging. Fast fluid-attenuated inversion recovery (FLAIR) sequences, magnetization transfer contrast (MTC) sequences, and MR cisternography were employed for selected patients. The signal intensity of the lesions relative to cerebrospinal fluid (CSF), the degree of lesion demarcation and the displacement of surrounding structures were evaluated. Proton density-weighted imaging depicted the lesions as hyper-intense to CSF with clearer delineation than T(1)- and T(2)-weighted imaging. Diffusion-weighted imaging depicted all lesions as strongly hyper-intense relative to CSF and brain tissue. FLAIR sequences depicted the lesions with mixed signal intensities but with poor-to-medium demarcation. MTC imaging increased delineation of the lesions to some degree. MR cisternography depicted the lesions as hypo-intense to CSF and clearly showed the anatomical relation to neighboring nerves and vessels. We concluded that diffusion-weighted imaging could specifically reveal an epidermoid at the CPA as a strongly hyper-intense lesion, and that MR cisternography is mandatory for preoperative planning.     

Intracranial meningeal hemangiopericytomas in children and adolescents: CT and MR imaging findings

Intracranial meningeal hemangiopericytomas in children and adolescents are prone to bleeding during surgery. CT and MR imaging may serve a role in preoperative diagnosis. The purpose of this report was to describe the radiologic findings in 9 pathologically proved cases of intracranial meningeal hemangiopericytomas in children and adolescents. The average duration of symptoms was short (mean, 4.0 months; median, 1.5 months). The intraoperative blood loss was large (mean, 3561 mL; median, 1000 mL). Tumors were extra-axial, irregularly multilobular, and hypervascular. Radiologically, they showed mixed attenuation on precontrast CT images, heterogeneous signal intensity on precontrast MR imaging, and marked and heterogeneous enhancement on postcontrast MR imaging. Bone erosion was sometimes present, but hyperostosis was not present. On MR imaging, multiple signal intensity voids of vessels were observed in 100% (8/8) of tumors with AVM-like signal intensity flow voids in 25% (2/8) of tumors. These results suggest that CT and MR imaging findings may be helpful for preoperative diagnosis.     

CT and MR imaging of intralabyrinthine schwannoma: report of two cases and review of the literature

Two cases of intralabyrinthine schwannoma were studied with computed tomography (CT) and magnetic resonance (MR) imaging. On CT scans, a soft-tissue mass was identified in the round window niche in both cases. Widening of the basilar turn of the cochlea and characteristic erosion of the promontory were noticed in one case. Preoperative MR imaging (performed in only one case) revealed a soft-tissue mass in the labyrnth, extending into the round window niche. Findings at CT and MR imaging are discussed, and a differential diagnosis is given. The literature is reviewed. The authors' findings suggest that CT and MR imaging may prove very valuable in the previously difficult preoperative diagnosis of these tumors. In the setting of progressive sensorineural hearing loss, atypical Meniere disease, or recurrent vertigo, the presence of a mass in the labyrinth or labyrinthine windows- delineated on CT or MR images, despite a normal internal auditory canal, cerebellopontine angle, or brain stem - is highly suggestive of intralabyrinthine schwannoma.     

Giant cell tumors of the tendon sheath may present radiologically as intrinsic osseous lesions

The purpose of this study was to explain radiographic features of giant cell tumors of the tendon sheath (GCTTS), in particular, osseous extension, by correlating imaging findings with histology in order to increase the accuracy of radiological diagnosis. In a series of 200 consecutive osseous (pseudo) tumors of the hand, on radiography, six patients presented with an intrinsic osseous lesion caused by a histologically confirmed neighboring GCTTS. Available radiographs, computed tomography (CT), and contrast-enhanced magnetic resonance (MR) images were correlated with histology. Radiography showed osseous lesions consisting of well-defined cortical defects in four (one of whom also demonstrated cortical scalloping) and a slightly expansile, well-defined osteolytic lesion in two patients. MR obtained in four patients showed the extraosseous tumor invading/eroding bone and causing cortical scalloping (three and one patients, respectively). Extension depicted on MR was confirmed on the two available resection specimens. All lesions were polylobular (cauliflower or mushroom like) and neighbored tendon sheaths. Dense collagen and hemosiderin-loaded macrophages explained the high CT attenuation and the low MR signal intensity on T2-weighted images that was observed in all four MR and in all two CT scans. The high density of proliferative capillaries explained the marked enhancement observed in all four patients with gadolinium (Gd)-chelate-enhanced MR imaging. GCTTS is a soft tissue (pseudo) tumor that may invade bone and as a consequence mimick an intrinsic osseous lesion on radiographs. In such cases, specific MR and CT features that can be explained by histological findings can be used to suggest the correct diagnosis.