MR imaging of the nasopharynx and floor of the middle cranial fossa. Part I. Normal anatomy

The normal anatomy of the nasopharynx and floor of the middle cranial fossa was analyzed with magnetic resonance (MR) imaging. MR images from five healthy volunteers were correlated with whole-organ cryomicrotome sections from three cadavers. Anatomic connections exist between the paranasopharyngeal spaces and the surface structures of the skull base. These anatomic connections include the intimate relationship between the eustachian tube and the pharyngobasilar fascia, the attachment of the muscles of mastication and deglutition to the skull base, and vascular and nervous structures in the foramina. The inherent contrast between the soft tissues of the nasopharynx and related structures and the bone of the floor of the middle cranial fossa allowed excellent visualization of these anatomic connections.     

Imaging findings in schwannomas of the jugular foramen

BACKGROUND AND PURPOSE: Tumors of the cranial nerve sheath constitute 5% to 10% of all intracranial neoplasms, yet few articles have described their CT and MR characteristics. We report the imaging findings in a relatively large series of schwannomas of the jugular foramen, contrasting them with other disease entities, especially vestibular schwannomas and tumors of the glomus jugulare. METHODS: CT and/or MR studies of eight patients who underwent surgery for histologically proved schwannomas were reviewed retrospectively. One additional patient with an assumed schwannoma of the jugular foramen, who did not have surgery, was also included. RESULTS: Surgical findings showed schwannomas of the glossopharyngeal nerve in seven patients and tumor involvement of both the glossopharyngeal and vagal nerves in one patient. All tumors were partially located within the jugular foramen. Growth extending within the temporal bone was typical. Tumor extended into the posterior cranial fossa in all nine patients and produced mass effect on the brain stem and/or cerebellum in seven patients; in five patients, tumor extended below the skull base. On unenhanced CT scans, tumors were isodense with brain in six patients and hypodense in two. In seven patients, CT scans with bone algorithm showed an enlarged jugular foramen with sharply rounded bone borders and a sclerotic rim. On MR images, T1 signal from tumor was low and T2 signal was high relative to white matter in all patients. Contrast enhancement on CT and/or MR studies was strong in eight patients and moderate in one. CONCLUSION: Schwannoma of the jugular foramen is characteristically a sharply demarcated, contrast-enhancing tumor, typically centered on or based in an enlarged jugular foramen with sharply rounded bone borders and a sclerotic rim. Intraosseous extension may be marked.     

Middle ear cholesteatoma extending into the petrous apex: evaluation by CT and MR imaging

CT and MR imaging findings were reviewed in four cases of acquired cholesteatoma of the middle ear that extended medially into the petrous apex and middle cranial fossa. In one case the lesion further extended anteromedially into the sphenoid sinus. CT demonstrated the lesions as nonenhancing hypodense masses with bone destruction, extending medially from the middle ear cavity to the petrous apex region. On MR imaging, the lesion was slightly hypointense relative to brain on T1-weighted images and hyperintense on T2-weighted images. MR imaging clearly delineated the extraaxial location of the lesion and associated brain displacement. The medial extension of the cholesteatomas seems to have proceeded via a detour around the bony labyrinth into the petrous apex region by following normal pathways of temporal bone pneumatization.     

鼻咽缝间隙的解剖学基础及其影像学表现和意义

目的 在影像上提出鼻咽缝间隙的概念，介绍其CT和MRI表现及其意义。方法 正常CT组43例，正常MRI组36例，均进行鼻咽轴面平扫，其中加做鼻咽冠状面CT和MR扫描各5例，7例加做鼻咽后壁矢状面MR薄层扫描；2例鼻咽轴位断面标本作对照；鼻咽癌（NPC）组30例，同时进行CT与MR扫描，对鼻咽后软组织结构影像学表现进行详细观察分析。结果 鼻咽缝间隙位于椎前并列的头长肌或颈长肌之间，咽后壁后方，枕骨及颈椎前方，它包括上述肌肉之间的咽缝、咽后间隙、危险间隙、椎前间隙部分和组成这些间隙的筋膜，以及其中的纤维结缔组织、脂肪和淋巴结等结构，在CT上表现为三角形不均匀低密度影，在MRI上，呈三角形不均匀高信号影，其正中有粗细不一的低信号咽缝。正常CT组43例均在椎前肌之间出现1个层面以上的、呈低密度的两侧对称的三角形影，为鼻咽缝间隙；在斜坡和硬腭水平之间均见鼻咽缝间隙者22例，部分层面显示鼻咽缝间隙者14例，鼻咽缝间隙达口咽水平者7例。正常MRI组36例，在轴面像上35例在椎前肌之间可见两侧对称的呈不均匀高信号的三角形鼻咽缝间隙；从斜坡至硬腭水平均见鼻咽缝间隙者13例，部分可见11例，鼻咽缝间隙达口咽水平者11例；矢状面像上，鼻咽缝间隙止于C2椎体上部者4例、下部者3例；冠状面像上，鼻咽缝间隙呈纵行条带状影2例，倒置梯形3例。2具鼻咽断面尸体标本均见鼻咽后壁后方并列的头长肌或颈长肌之间三角形疏松纤维结缔组织。NPC组30例中鼻咽缝间隙对称存在者14例，不对称性变窄1例，消失者15例。结论 鼻咽部椎前并列的头长肌或颈长肌之间的结构在CT和MRI上统称为鼻咽缝间隙是合适的；NPC患者的鼻咽缝间隙消失和不对称性变窄多提示肿瘤侵犯椎前肌，而对称存在时，肿瘤多位于鼻咽顶后壁浅层。     

Chronic inflammatory disease of the middle ear cavities: Gd-DTPA-enhanced MR imaging

Twenty-seven patients with chronic middle ear infection were prospectively studied with pre- and post-contrast magnetic resonance (MR) images to assess the role of MR imaging in the recognition of middle ear tissue abnormalities. The findings were correlated with computed tomographic (CT) scans and surgical and pathologic data. Granulation tissue constantly appeared enhanced on studies done with gadolinium diethylenetriaminepentaacetic acid (DTPA), unlike cholesteatoma, cholesterol granuloma, or brain herniation into the middle ear cavities. Evaluation of extension and thickness of the inflammatory tissue with MR imaging was in accordance with surgical findings. In six cases, isolated granulation tissue misdiagnosed as either a cholesteatoma or herniated brain on CT scans was accurately evaluated on postcontrast MR images. When granulation tissue was associated with other soft-tissue masses, Gd-DTPA-enhanced MR images allowed accurate definition of the site and the extension of each lesion. Furthermore, abnormal meningeal enhancement was precisely depicted by MR images in two cases.     

CT and MR imaging of solitary extramedullary plasmacytoma of the nasal tract

BACKGROUND AND PURPOSE: Solitary extramedullary plasmacytoma (SEP) is rare. The purpose of this study was to determine the CT and MR imaging features of SEP of the nasal tract. METHODS: We retrospectively reviewed three CT and two MR images of three histologically proved cases in two men and one woman aged 43-66 years. RESULTS: The plasmacytomas predominantly involved the nasopharynx in two cases and the nasal cavity in one. Two of the tumors were bulky solid masses, whereas the third showed infiltrative features. They were predominantly masses or infiltrative lesions with soft-tissue attenuation on CT scans. The lesions were isointense and hyperintense on T1- and T2-weighted MR images, respectively. The tumors revealed moderate-to-marked contrast enhancement and may have been associated with lytic bone destruction. CONCLUSION: The imaging features of SEP are nonspecific. However, this entity should be included in the differential diagnosis of tumors in the nasopharynx and nasal cavity.     

Tumors of the nasopharynx and adjacent areas: MR imaging with Gd-DTPA

The purpose of this study was to describe our experience with Gd-DTPA-enhanced MR imaging in the evaluation of the most common nasopharyngeal tumors. Forty-two patients with tumors of the nasopharynx and adjacent spaces had MR imaging before and after IV injection of Gd-DTPA. Images were obtained with a 1.0-T superconducting magnet imaging system in transverse, coronal, and sagittal planes with T1- and T2-weighted sequences. MR images were compared with CT scans and tumor histology. The studies were categorized by using a grading system with grades ranging from unsatisfactory (grade 0) to optimal (grade 3). Contrast-enhanced MR enables better identification of small anatomic details such as both palatini muscles and the pharyngobasilar fascia. MR after Gd-DTPA was superior to CT in all cases except for tumors of the maxillary sinuses. MR with Gd-DTPA is recommended for tumors that are small and difficult to detect on the initial nonenhanced MR examination or that show subtle infiltrations. Because of the increased cost and longer examination time, MR with Gd-DTPA does not need to be done when large tumors are well delineated.     

Tumors of the nasopharynx and adjacent areas: MR imaging with Gd-DTPA

The purpose of this study was to describe our experience with Gd-DTPA-enhanced MR imaging in the evaluation of the most common nasopharyngeal tumors. Forty-two patients with tumors of the nasopharynx and adjacent spaces had MR imaging before and after IV injection of Gd-DTPA. Images were obtained with a 1.0-T superconducting magnet imaging system in transverse, coronal, and sagittal planes with T1- and T2-weighted sequences. MR images were compared with CT scans and tumor histology. The studies were categorized by using a grading system with grades ranging from unsatisfactory (grade 0) to optimal (grade 3). Contrast-enhanced MR enables better identification of small anatomic details such as both palatini muscles and the pharyngobasilar fascia. MR after Gd-DTPA was superior to CT in all cases except for tumors of the maxillary sinuses. MR with Gd-DTPA is recommended for tumors that are small and difficult to detect on the initial nonenhanced MR examination or that show subtle infiltrations. Because of the increased cost and longer examination time, MR with Gd-DTPA does not need to be done when large tumors are well delineated.     

颅底脊索瘤的CT和MRI影像诊断与鉴别诊断

目的探讨颅底脊索瘤CT与MR影像学诊断与鉴别诊断。方法回顾性分析13例经病理证实的颅底脊索瘤的CT与MR影像学资料。结果13例脊索瘤中,发生在斜坡5例,鞍区4例,颅中凹2例,鼻咽部1例,蝶窦1例。肿瘤的形态以不规则形最多8例,圆形3例,椭圆形2例。病灶边界清楚9例,边缘模糊4例。MR表现为T1WI呈低、等、高混杂信号,T2WI则以高、低混杂信号为主。增强后病灶呈轻到中度强化,强化信号不均匀。CT见病灶呈不均匀等或稍高密度肿块,7例可见不同程度的骨质破坏。结论颅底脊索瘤的CT和MR表现有一定的特征性,结合临床大多可以确诊,但需与脑膜瘤、垂体瘤、鼻咽癌、软骨类肿瘤等鉴别。     

Cross-sectional imaging of primary osseous hemangiopericytoma

The aim of this study was to assess cross-sectional imaging features and the value of CT and MRI in primary hemangiopericytoma of bone. In five patients with histologically proven primary osseous hemangiopericytoma CT and MR scans were evaluated retrospectively. Both CT and MRI were available in four patients each. In three patients both imaging techniques were available. On CT primary hemangiopericytoma of bone presents as an expansive lytic lesion with bone destruction and inhomogeneous contrast enhancement. Magnetic resonance imaging depicts osseous hemangiopericytoma as hyperintense lesion on T2-weighted images with intermediate signal intensity on T1-weighted images. Curvilinear tubular structures of signal void in the tumor matrix on T1-weighted images and corresponding hyperintense structures on T2-weighted and on fat-suppressed short tau inversion recovery images were present in three patients. Although cross-sectional imaging findings are non-specific, they add to the diagnosis and provide valuable information about the extent of bone destruction and local tumor spread in patients with primary osseous hemangiopericytoma. While CT demonstrates the extent of bone destruction best, MRI better visualizes medullary and soft tissue extension of the tumor. Curvilinear signal abnormalities support the diagnosis of hemangiopericytoma of bone. This imaging pattern is best visualized on fat-suppressed or contrast enhanced T1-weighted MR images.     

Adenocarcinoma of the pancreatic ducts: comparative evaluation with CT and MR imaging at 1.5 T.

A prospective comparison of computed tomography (CT) and magnetic resonance (MR) imaging at 1.5 T was performed in 50 patients with the suspected diagnosis of pancreatic carcinoma. CT scans were obtained before and after administration of contrast material in 41 of 50 patients (82%); 34 of 41 postcontrast scans (83%) were obtained with dynamic CT. MR images were interpreted without knowledge of the results of CT, ultrasound, cholangiography, or endoscopic retrograde cholangiopancreatography in 48 patients (96%). Surgical correlation of findings at CT and MR imaging was performed in 24 patients (48%) at laparotomy and in two patients (4%) at autopsy. On T1-weighted MR images, relatively diminished signal intensity of tumor compared with that of the adjacent pancreas was a consistent finding. MR imaging proved superior to CT in identification of pancreatic carcinoma (particularly in smaller intrapancreatic tumors), peripancreatic extension, vascular and portal vein invasion, and duodenal invasion. These results suggest that MR imaging of the pancreas is superior in many instances to CT in preoperative evaluation of pancreatic carcinoma.     

Spondylolysis, spondylolisthesis, and associated nerve root entrapment in the lumbosacral spine: MR evaluation.

Spondylolysis is defined as a bone defect in the pars interarticularis. Its cause is uncertain but is believed in most cases to be related to repeated stress, trauma, or both. Findings of spondylolysis on conventional radiographs and on CT scans have been well characterized. Although these imaging techniques remain effective for the diagnosis of this defect, MR imaging is increasingly used as the primary or sole imaging method in patients with lower back pain and radiculopathy. Therefore, because MR images of the lumbar spine may be interpreted in the absence of correlative CT scans or conventional radiographs, the MR features of spondylolysis and its associated findings must be recognized. This essay illustrates the MR findings of lumbosacral spondylolysis and associated entrapment and direct impingement of the spinal nerve root.     

Orbital lymphoma. Role of CT and MRI

CT and MRI have made it possible to make a strongly presumptive diagnosis of orbital lymphoid tumors. Orbital lymphomas are usually homogeneous masses of relatively high density and sharp margins. The lesions mold themselves to pre-existing structures without eroding the bone. On MR imaging, they appear as relatively hypointense images, particularly in T1-weighted MR scans.     

乳头状内淋巴囊瘤的影像学表现

目的 探讨乳头状内淋巴囊瘤的CT、MRI和DSA特征。方法 回顾性分析总结5例组织病理学证实的乳头状内淋巴囊瘤的CT骨破坏特点及MRI信号特征、强化方式、血液流空情况，4例同时进行DSA检查，以观察血供状态。CT采用常规横轴面平扫和增强扫描；MRI采用SE和快速自旋回波（FSE）及脂肪抑制序列，行矢状、冠状和横轴面平扫和增强扫描。结果 （1）CT表现：肿瘤呈中心位于颞骨岩部迷路后区的溶蚀性骨破坏，病变内含钙化。（2）MRI表现：在未增强T1WI和T2WI，5例肿瘤内见不规则形低信号影，其中心位于颞骨岩部中后部的前庭管外口周围区；3例肿瘤周边显示高信号缘；2例囊实性肿瘤的囊性部分呈高信号，脂肪抑制像高信号不被抑制，而且其边缘更清楚；5例瘤内均见血管流空影。（3）DSA显示肿瘤主要由颈外动脉的分支供血。其中2例还有小脑前下动脉参与供血。结论 乳头状内淋巴囊瘤是位于颞骨岩部迷路后区的具有侵袭性、溶骨性、富含血管的肿瘤，它的影像学特征结合发生部位有助于诊断及鉴别诊断。     

MRI and CT findings of the giant cell tumors of the skull; five cases and a review of the literature

PURPOSE: To investigate CT and MR findings of giant cell tumors (GCTs) of the skull, an unusual site for such tumors. MATERIALS AND METHODS: CT and MR features of five histologically proven giant cell tumors of the skull were retrospectively reviewed. We also reviewed 22 cases in the literature that included MR or CT findings. RESULTS: Three of the tumors originated from the temporal bone with predominantly medial extension, and the other two were centered in the body of the sphenoid bone and featured symmetrical soft tissue extension. CT images with bone window settings showed reactive bone changes for all three tumors of the temporal bone, suggesting slow growth for example, an expanded intradiploic space, expansive remodelling and development of foci of pressure erosion. GCTs of the sphenoid bone showed purely osteolytic changes without remodelling. Although the MR signals and enhancement patterns varied, all the tumors of the temporal bone had a markedly low intensity area on T2-weighted images, which was not seen in the tumors of the sphenoid bone. The findings for our cases generally corresponded to those reported in the literature. CONCLUSION: Giant cell tumors of the skull have two preferential sites and may have characteristic tendencies as to their extent. Bone changes and MR signals appear to show differences between the two sites.     

Infantile fibromatosis of the neck with intracranial involvement: MR and CT findings.

CT and MR imaging studies were performed in a 3-year-old boy with infantile fibromatosis arising from the infratemporal fossa and extending into the middle cranial fossa. On CT scans, the lesion was hyperattenuating (44-49 Hounsfield units [HU]), enhancing significantly after application of contrast material (63-66 HU). The MR images showed a multilobulated lesion of heterogeneous signal intensity. The tumor was markedly hypointense on T2-weighted images and slightly hypointense on T1-weighted images relative to brain tissue, iso- or slightly hyperintense relative to tongue muscle on both T2- and T1-weighted images, and enhanced strongly after administration of gadopentetate dimeglumine.     

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.     

Leptomeningeal metastasis: MR imaging

Seven patients with central nervous system neoplasia and leptomeningeal metastases, proved either at initial diagnosis or on follow-up with contrast material-enhanced computed tomography (CT), were evaluated with magnetic resonance (MR) imaging. In two patients, diffuse sulcal enhancement on CT scans was inapparent on T1- or T2-weighted MR images. Likewise, in four patients diffuse cisternal enhancement on CT scans was not identifiable with MR. Nodular or focal cisternal masses were identified with both CT and MR imaging in three patients; in two, however, MR imaging provided less information. Ependymal and subependymal metastases identified with CT (two patients) were indistinguishable on MR images from periventricular abnormalities of radiation therapy and/or hydrocephalus. These findings suggest that leptomeningeal metastasis may be so subtle or inapparent as to be overlooked with MR imaging alone. Thus, CT and MR imaging should be considered complementary techniques for initial diagnosis and follow-up of tumors with a propensity for leptomeningeal metastasis.     

Detection of ACTH-producing bronchial carcinoid tumors: MR imaging vs CT.

Adrenocorticotrophic hormone (ACTH)-producing bronchial carcinoid tumors tend to occur in the middle third of the lung adjacent to pulmonary vessels. Because they cause signs and symptoms when quite small (by virtue of their ACTH production), they may not be detected by CT. MR imaging was performed in 10 consecutive patients with surgically proved ACTH-producing bronchial carcinoid tumors in order to test the ability of MR to clarify equivocal or indeterminate findings on CT examinations. All bronchial carcinoid tumors had high signal intensity on T2-weighted and short-inversion-time inversion-recovery images, facilitating their distinction from pulmonary vasculature. In eight patients, the CT and MR images were equivalent in the detection of bronchial carcinoid tumors. In two patients, MR showed tumors in the middle third of the lung that were equivocal on CT. MR imaging may distinguish small bronchial carcinoid tumors from adjacent pulmonary vessels in the central third of the lung at a time when the CT study is nondiagnostic or equivocal.     

Overlapping thin-section fast spin-echo MR of the large vestibular aqueduct syndrome.

PURPOSETo evaluate a high-resolution, thin-section fast spin-echo MR imaging technique of the inner ear to identify the large vestibular aqueduct syndrome seen on temporal bone CT scans.METHODSWe retrospectively reviewed the temporal bone CT scans of 21 patients with hearing loss and enlarged bony vestibular aqueducts by CT criteria. High-resolution fast spin-echo MR imaging was then performed on these patients using dual 3-inch phased-array receiver coils fixed in a temporomandibular joint holder and centered over the temporal bones. MR imaging included axial and oblique sagittal fast spin-echo sequences. The diameter of the midvestibular aqueduct on CT scans and the signal at the level of the midaqueduct on MR images were measured on axial sequences, then compared. High-resolution MR imaging with the same protocol was performed in 44 control subjects with normal ears, and similar measurements were taken.RESULTSThe average size of the enlarged bony vestibular aqueduct on CT scans was 3.7 mm, and the average width of the signal from within the enlarged aqueduct on MR images was 3.8 mm. Statistical analysis showed excellent correlation. MR images alone displayed the enlarged extraosseous endolymphatic sac, which accompanies the enlarged aqueduct in this syndrome. Five ears in three patients with enlarged bony vestibular aqueducts on CT scans showed no evidence of an enlarged endolymphatic duct or sac on MR images. An enlarged endolymphatic sac was seen on MR images in one patient with a bony vestibular aqueduct, which had normal measurements on CT scans. MR imaging alone identified a single case of mild cochlear dysplasia (Mondini malformation). In the 88 normal ears studied, the average size of the endolymphatic sac at its midpoint between the common crus and the external aperture measured on MR images was 0.8 mm (range, 0.5 to 1.4 mm). In 25% of the normal ears, no signal was seen from within the vestibular aqueduct.CONCLUSIONThin-section, high-resolution fast spin-echo MR imaging of the inner ear is complementary to CT in studying patients with the large vestibular aqueduct syndrome, as MR imaging better displays the soft tissue and fluid of the membranous labyrinth.