Tumoral thrombosis of cerebral venous sinuses: preoperative diagnosis using magnetic resonance phase imaging.

Intracranial, dural-based neoplasms will not infrequently invade adjacent venous sinuses. Therefore, the preoperative diagnosis of venous invasion is important, as it will alter the surgical approach to the lesion. Magnetic resonance imaging is a noninvasive means of visualizing the cerebral venous sinuses. The preoperative diagnosis of venous thrombosis can, however, be difficult and confusing with conventional spin-echo magnetic resonance imaging because of variable appearances produced by blood clot degradation products as well as flowing blood. Phase magnetic resonance imaging is a simple method that can be acquired simultaneously with conventional spin-echo sequences, and is based primarily on whether protons are stationary or moving. In the context of venous sinus occlusion, phase imaging can demonstrate the presence or absence of blood flow more easily than spin-echo imaging. Three cases of dural-based neoplasms are presented that demonstrate the utility of phase imaging in diagnosing tumoral occlusion of the venous sinuses.

Intracranial vascular abnormalities: value of MR phase imaging to distinguish thrombus from flowing blood.

The interpretation of conventional spin-echo and gradient-echo MR images of intracranial vascular lesions can be complex and ambiguous owing to variable effects on image intensity caused by flowing blood or thrombus. MR phase images, obtained simultaneously with conventional-magnitude images, are useful for evaluating proton motion (i.e., blood flow), and therefore can simplify the diagnosis of the presence or absence of thrombosis within a vascular structure or lesion. Fourteen patients with a variety of intracranial vascular abnormalities (aneurysms, superior sagittal sinus thrombosis, neoplasms adjacent to venous sinuses, and vascular malformations) were evaluated with conventional MR and phase imaging for the presence of blood flow. The phase images correlated with angiography in all cases. Phase imaging was not necessarily better than conventional spin-echo imaging in all cases, but it simplified the evaluation of thrombus vs blood flow in many. In three of five aneurysms, the phase images were diagnostic for evaluating lumen patency whereas the conventional images were ambiguous. Phase imaging was advantageous for detecting tumor invasion of the venous sinus when venous blood was enhanced by gadopentetate dimeglumine. A laminar flow phantom experiment determined the lower limits of sensitivity of phase imaging to be 0.5 cm/sec in the slice-select and 2.5 cm/sec in the read gradient directions. Phase imaging is a simple, reliable technique that can distinguish thrombosis from flowing blood within intracranial lesions. It is easily performed and adds no additional time to the MR examination.

CT and MR imaging of the central skull base. Part 2. Pathologic spectrum.

The radiologist must have a thorough knowledge of the normal anatomy and the pathologic spectrum of the skull base to determine the extent of abnormality and to help plan the surgical approach. The authors describe and present examples of congenital, benign, and malignant lesions that affect this region, including cephalocele, fracture, fistula, juvenile angiofibroma, meningioma, chordoma, pituitary adenoma, chondrosarcoma, nasopharyngeal carcinoma, and rhabdomyosarcoma. Metastatic, infectious, and other miscellaneous processes are also discussed. Imaging strategies with computed tomography and magnetic resonance imaging to aid in the diagnosis are suggested.

CT and MR imaging of the central skull base. Part 1: Techniques, embryologic development, and anatomy.

Recent advances in surgical techniques have enabled surgeons to approach previously inoperable deep-seated lesions of the skull base. The radiologist requires a thorough knowledge of the normal anatomy and the pathologic spectrum of this region and an understanding of imaging modalities in order to determine the extent of pathologic conditions and help plan the surgical approach. The embryologic development of the central skull base, normal gross anatomy, and anatomy as seen on computed tomographic and magnetic resonance images are presented.

MR imaging appearance of childhood adrenoleukodystrophy with auditory, visual, and motor pathway involvement.

Childhood adrenoleukodystrophy is an X chromosome-linked disorder characterized by progressive demyelination of cerebral white matter and adrenal insufficiency. Magnetic resonance (MR) imaging was performed in 15 patients with symptomatic disease and three with presymptomatic disease. MR imaging findings were abnormal only in symptomatic patients. Major sites of disease were the occipital, parietal, and temporal lobes, with all patients showing involvement of occipital lobes, optic radiations, and splenium of the corpus callosum. Follow-up images obtained in four patients demonstrated a posterior-to-anterior progression of disease. Correlation of results from MR imaging with those from evoked potential studies indicated that MR imaging was the method of choice for detecting demyelination of visual, auditory, and motor systems in adrenoleukodystrophy.

Perineural tumor extension through the foramen ovale: evaluation with MR imaging.

Perineural tumor extension is a form of metastatic disease in which primary tumors spread along neural pathways and gain access to non-contiguous regions. The treatment and prognosis are altered when perineural extension occurs. Awareness and proper evaluation are critical for the radiologist. The third (mandibular) division of the trigeminal nerve (V3), passing through the skull base via the foramen ovale, is a common route of perineural spread of head and neck lesions. Seven patients with perineural tumor involvement of the mandibular nerve were evaluated with magnetic resonance imaging with use of standard spin-echo pulse sequences emphasizing T1-weighted information. Three patients had adenoid cystic carcinoma, three had squamous cell carcinoma, and one had well-differentiated lymphocytic lymphoma of the orbit. MR imaging signs of perineural involvement included smooth thickening of V3, concentric expansion of the foramen ovale, replacement of the normal trigeminal cistern hypointensity by an isointense mass, lateral bulging of cavernous sinus dural membranes, and atrophy of masticator muscles.

MRI of intracranial sinovenous thrombosis: the role of phase imaging.

Conventional spin-echo magnetic resonance (MR) imaging of venous thrombosis is complicated by the variable appearance produced by the stage of blood clot degradation and velocity of blood flow. Phase MR imaging is a simple method based primarily on whether protons are stationary or moving. A case of superior sagittal sinus thrombosis demonstrates the utility of phase imaging.

MRI of the nasopharynx.

Magnetic resonance imaging with its superior soft tissue contrast resolution and absence of beam hardening artifacts, combined with its ability to perform multiplanar imaging, is now the method of choice for the primary evaluation of the patient who presents with suspected nasopharyngeal pathology. The relative ease (compared to CT) of localization of the primary process coupled with the exquisite definition of the extent of disease allows the radiologist to play an even more important role in the diagnosis and management of patients presenting with nasopharyngeal disease.

Spinal abnormalities in pediatric patients: MR imaging findings compared with clinical, myelographic, and surgical findings.

Eighty-one pediatric patients with a variety of spinal disorders, including suspected dysrhaphism, scoliosis, neoplasia, and neurofibromatosis, underwent magnetic resonance (MR) imaging. The results were retrospectively compared with those of myelography followed by computed tomography (CT) and surgery. In patients with dysrhaphism, most abnormalities, including hydromyelia, inclusion tumors, and sites of cord tether, were demonstrated with MR imaging. Diastematomyelia and small hydromyelic cavities were indistinguishable on routine coronal and sagittal T1-weighted images; axial images with T2 weighting were optimal for this differentiation. MR imaging did not enable direct visualization of a thickened filum or evaluation of tethering with a thin, dorsally positioned neural placode. Congenital or severe scoliosis required lengthy studies with multiple planes of imaging or myelography and CT. Milder curvatures were readily evaluated with MR imaging, and neoplastic lesions, with the exception of intrathecal tumor seeding, were adequately defined.

A phantom study of intracranial CSF signal loss due to pulsatile motion.

MR imaging of the head often reveals localized areas of decreased signal intensity (flow voids) within the CSF. These flow voids are caused by turbulence within the CSF resulting from its pulsatile back-and-forth flow through the cerebral aqueduct and foramina. We describe a phantom that mimics the essential features of the CSF flow, and discuss its use in studying the dependence of the CSF flow void (CFV) on spin-echo (SE) and inversion-recovery pulse sequence parameters. The phantom had fluid-filled spaces to represent ventricles, and channels connecting these spaces to represent the aqueduct and foramina. A pump pushed the fluid in a pulsing manner through the phantom at various rates. The CFV was quantified by measuring signal loss relative to nonflowing fluid. The CFV did not appear to depend on repetition time or inversion time. The CFV was, however, strongly dependent on echo time (TE), and for single-echo SE sequences CFV became less severe as TE decreased. An even-echo rephasing effect was observed for multiecho sequences. Slice thickness and field of view also affected the appearance of the CFV, as did gating with respect to the pulsatile motion. These results imply that TE, field of view, slice thickness, and gating must be considered when using the appearance or absence of the CFV in diagnosis.

Tumors of the parapharyngeal space and upper neck: MR imaging characteristics.

Magnetic resonance (MR) imaging characteristics of 40 tumors involving the parapharyngeal space and the upper part of the neck were reviewed. These lesions could be classified as being either hypervascular (glomus tumors or metastatic kidney, thyroid, or venous hemangiomas) or hypovascular (salivary gland tumors, neurogenic tumors, lymphomas, sarcomas). Detailed analysis of the contour of the neoplasm combined with clinical findings allowed further refinement of the differential diagnosis in each category. Most lesions had an intermediate signal intensity on T1-weighted images and a fairly high signal intensity on T2-weighted images. Hypervascular tumors had a number of "channel voids" caused by high-flow vessels on T1- and T2-weighted images, and on T2-weighted images there were areas of high signal intensity, presumably due to sites of slow flow within the image plane. The hypovascular lesions were quite homogeneous, and it was therefore more difficult to differentiate among the neoplasms in this group.

Gadolinium-DTPA and MR imaging of pituitary adenoma: a preliminary report.

Gadolinium-DTPA MR imaging (Gd-MR), unenhanced MR imaging, and contrast-enhanced CT studies were compared prospectively in six patients with surgically confirmed pituitary adenomas and three patients without sellar pathology to determine the utility of Gd-MR in the diagnosis of pituitary adenoma. In normal patients, the pituitary gland, cavernous sinus, and infundibulum enhanced by T1 shortening after gadolinium. In adenoma patients, two of four focal lesions identified with contrast-enhanced CT were identified with Gd-MR, and one was identified with unenhanced MR. The earliest short repetition-time sequence performed after gadolinium injection was best for focal lesion detection. Normal cavernous sinus enhancement by gadolinium made identification of cavernous sinus extension of adenoma difficult. Infundibulum displacement was better seen with contrast-enhanced CT (two vs one); however, unenhanced and Gd-MR were better than contrast-enhanced CT for demonstrating chiasmal compression (four vs three). Contrast-enhanced CT, Gd-MR, and plain MR were equally able to identify gland enlargement, sellar floor erosion, and abnormalities of the diaphragma sellae. In this preliminary series, we found Gd-MR to be promising for imaging adenomas; however, modifications in Gd-MR technique including thinner slices and immediate scanning after gadolinium injection are necessary for the best detection of focal lesions.

Parotid masses: MR imaging.

Twenty patients with surgically proved neoplasms of the parotid gland were evaluated in order to compare contrast material-enhanced computed tomography (CT) and magnetic resonance (MR) imaging. In 14 patients both CT and MR imaging examinations were performed, while in six only MR imaging was performed. Because contrast resolution is better with MR imaging, it appears to be superior to CT in distinguishing the parotid gland from surrounding structures. Four intraparotid lesions were more conspicuous on T2-weighted MR images than on CT scans. MR imaging appears to be superior to CT for evaluating parotid masses and for distinguishing neoplasms of the parotid gland from those originating within the parapharyngeal space.

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.

MR imaging of pituitary adenoma: CT, clinical, and surgical correlation.

Twenty-five patients with suspected pituitary adenoma were evaluated prospectively with CT and MR. Nine patients underwent transsphenoidal surgery, and three of these showed a documented decrease in size of mass on bromocriptine therapy. CT was more sensitive than MR for detecting focal lesions (seven vs three) and sellar-floor erosion (12 vs six). MR was superior to CT in identifying infundibular abnormalities (seven vs six), focal abnormalities of the diaphragma sellae (10 vs seven), cavernous sinus invasion (four vs two), and optic chiasm compression (six vs zero). Thus, MR may be the procedure of choice for optimal identification and localization of macroadenoma. For patients with suspected microadenoma, however, this preliminary series indicates that CT remains the radiographic procedure of choice.

Mastoid size determined with lateral radiographs and computerized tomography.

Minimal pneumatization of the temporal bone is characteristic of otitis media. The classic radiographic assessment of mastoid air cell system size is the Runström II view, but the Law lateral view is the commonly used clinical view in the United States. Isolated temporal bone specimens are most accurately positioned using a modified Law Lateral view (with the film perpendicular to the central X-ray beam). Computerized tomography is the best radiographic means of assessing mastoid pneumatization. The mathematical relationships of mastoid pneumatization size determined by the Runström II, Law, and modified Law lateral radiographs, and computerized tomography were determined in 30 adult cadaver specimens. These data may facilitate additional study of otitis media.

MR of Leigh's disease (subacute necrotizing encephalomyelopathy).

MR images of three patients with Leigh's disease (subacute necrotizing encephalomyelopathy) were compared with CT findings. In all patients typical lesions in the basal ganglia were identified with both MR and CT. In two patients MR permitted identification of additional lesions not detected with CT. In one patient progression of MR abnormalities over a 4-month period correlated well with clinical deterioration in neurologic status. T2-weighted images with a repetition time (TR) greater than 1950 msec and an echo time (TE) greater than or equal to 60 msec or inversion-recovery images with a 50-msec TE, 1213-msec inversion time, and 3000-msec TR were advantageous in identifying multiple necrotic lesions in the brainstem, deep gray matter, periventricular white matter, and cerebral cortex. In this series MR was more sensitive in detecting and localizing multifocal necrotic lesions of Leigh's disease than CT was, and thus may be a useful diagnostic tool for patients with the appropriate clinical and laboratory abnormalities.

Mastoid size determined with lateral radiographs and computerized tomography.

Minimal pneumatization of the temporal bone is characteristic of otitis media. The classic radiographic assessment of mastoid air cell system size is the Runstrom II view, but the Law lateral view is the commonly used clinical view in the United States. Isolated temporal bone specimens are most accurately positioned using a modified Law lateral view (with the film perpendicular to the central X-ray beam). Computerized tomography is the best radiographic means of assessing mastoid pneumatization. The mathematical relationships of mastoid pneumatization size determined by the Runstrom II, Law, and modified Law lateral radiographs, and computerized tomography were determined in 30 adult cadaver specimens. These data may facilitate additional study of otitis media.