Computed tomography of the buccomasseteric region: 1. Anatomy.

The differential diagnosis to consider in a patient presenting with a buccomasseteric region mass is rather lengthy. Precise preoperative localization of the mass and a determination of its extent and, it is hoped, histology will provide a most useful guide to the head and neck surgeon operating in this anatomically complex region. Part 1 of this article describes the computed tomographic anatomy of this region, while part 2 discusses pathologic changes. The clinical value of computed tomography as an imaging method for this region is emphasized.

Dense cystic craniopharyngiomas.

Characteristic computed tomographic (CT) findings of craniopharyngioma include calcification, contrast enhancement, and cyst formation. Sharp margins associated with a hypodense centrum usually characterize the CT appearance of a cystic tumor. The appearance of "dense" cysts in craniopharyngiomas has not been emphasized. Four cases of craniopharyngiomas with isodense to hyperdense cysts are reported. Comparative biochemical and in vitro CT analysis of cyst aspirates taken from these lesions demonstrate that high intracystic protein concentration accounts for the greater part of the hyperdensity. Various mechanisms for intracystic protein accumulation are discussed. Lesion characteristics, and not necessarily attenuation coefficients, are stressed in differentiating "dense" cystic from solid craniopharyngiomas.

A prospective comparison of duplex sonography vs angiography of the vertebral arteries.

A prospective blind comparison was completed between duplex sonography and angiography of the vertebral arteries. Thirty-two vertebral arteries were studied for direction of flow, degree of origin plaque or stenosis, Doppler characteristics, and vessel size. The vertebral arteries were reliably identified by imaging their course from the subclavian artery into the transverse foramina and by identifying a Doppler signal similar in waveform to the internal carotid artery. With Doppler, a 90% accuracy was obtained for direction of blood flow. Nonvisualization of origins was primarily due to vessel depth and/or tortuosity. In 12 vessel origins that were well seen with both techniques, angiography and sonography agreed in two-thirds of the cases. In four cases, origin plaque was underestimated with duplex imaging. Interestingly, no Doppler frequency or velocity elevation was identified distal to significant stenoses. One false-positive diagnosis of occlusion occurred with sonography, in which a 99% origin stenosis resulted in no detectable Doppler signal. By comparing sonography with angiography, sonography was shown to be 80% accurate in determining vertebral artery size. Our preliminary results indicate that duplex scanning is a reasonably accurate screening technique for size, patency, and direction of blood flow in the vertebral arteries. Duplex evaluation of the vertebral artery origin was limited by vessel depth, tortuosity, and calcifications.

The value of unenhanced scans in differentiating lesions producing ring enhancement.

Ring enhancement with contrast material is a nonspecific computed tomographic finding seen in a variety of lesions, including benign and malignant neoplasms, inflammation, infarction, and hematoma. This lack of specificity is especially troublesome in the differentiation of self-limiting disorders (infarction and hematoma) from progressive processes (tumor or abscess) potentially requiring surgical treatment. To determine whether more specific diagnoses were possible, 115 cases with ring lesions were retrospectively evaluated for the usefulness of precontrast scan features. The presence or absence of a complete ring proved useful. A complete ring on unenhanced scans effectively excluded self-limiting processes; it was seen in none of 18 infarcts or 11 hematomas. A complete ring on unenhanced scans occurred in 37 of 65 neoplasms, and was more common in metastatic disease (2:1) than in gliomas. A complete ring on unenhanced computed tomography was also seen in four of 15 pyogenic abscesses.

Computed tomography of the buccomasseteric region: 2. Pathology.

Part 2 of this article concerns itself with alterations in the normal anatomy (described in part 1) by various disease processes. Ten patients are described with various facial masses. The role of computed tomography in the clinical workup of these patients is stressed.

The behavior of Pantopaque on MR: in vivo and in vitro analysis.

MR imaging is considered by many to be the procedure of choice in imaging the spinal cord; yet we encountered an important pitfall of this procedure in the form of a patient with retained intraspinal Pantopaque. The results of this case are presented as well as those obtained in another patient with retained Pantopaque. Also described is the behavior of this contrast material when using in vitro imaging data obtained from a CSF/Pantopaque phantom. When T1-weighted imaging sequences are used, Pantopaque gives a high signal and CSF gives a low signal. With long repetition time, (e.g., 4000 ms), the CSF signal is high and the Pantopaque signal is not. With repetition time around 1000 to 2000, both may be isointense. The implications of these findings are discussed.

Comparison of radiographic quality and adverse reactions in myelography with iopamidol and metrizamide.

A randomized double-blind study was conducted to compare the radiographic quality and adverse reactions in myelography of the two nonionic water-soluble contrast media, iopamidol and metrizamide. A total of 46 myelograms were obtained, 28 with iopamidol and 18 with metrizamide. Untoward reactions consisted of nausea, headaches, back and leg pain, neuropsychiatric findings, and urinary retention. Iopamidol caused no reactions in 20 of the 28 cases, while metrizamide caused no reactions in only three of 18 cases. Film quality evaluation showed 22 of the 28 studies with iopamidol were judged excellent, whereas only 11 of the 18 metrizamide studies were judged excellent. The results of this study suggest that iopamidol produces better quality studies with fewer and milder adverse reactions than metrizamide.

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.

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.

Value of computed tomographic myelography in the recognition of cervical herniated disk.

Three patients with cervical radicular symptoms and normal metrizamide myelograms underwent thin-section high-resolution computed tomographic scanning because of a strong clinical suspicion of herniated disk. Herniated disk was demonstrated in all three cases. In two, the disk protrusions were recognized only by computed tomographic myelography, and in the third case, the diagnosis was made with plain computed tomography and confirmed by computed tomographic myelography.

CT-surgical correlation in pituitary adenomas: evaluation in 113 patients.

A retrospective study was undertaken in 113 patients with surgically proven pituitary adenomas to correlate the frequency, type, and location of computed tomographic (CT) abnormalities with surgical findings. There were 63 prolactin-secreting, 19 growth-hormone-secreting, 12 adrenocorticotropic-hormone-secreting, two thyroid-stimulating-hormone-secreting, and 17 nonfunctioning adenomas. The 51 functioning and nonfunctioning macroadenomas had similar CT appearances. Only 34 secretory adenomas presented as discrete, focal, hypodense lesions; the rest were isodense with the adjacent pituitary gland. Secretory adenomas were clinically apparent earlier, and accordingly the abnormalities seen on CT were less developed. The location of the normal pituitary gland could not be determined by attenuation characteristics; only by infundibulum displacement or opposite to a discrete, focal, hypodense lesion could the gland location be predicted reliably. Adenomas with hemorrhage, infarction, and cyst formation were indistinguishable from those without these findings. CT was helpful in identifying the mass effect of macroadenomas; however, in microadenomas of all types CT abnormalities were uncommon. Thus, the diagnostic evaluation of the patient suspected of harboring a pituitary adenoma, particularly a microadenoma, must remain a joint effort based on clinical, radiographic, and endocrinologic data.

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.

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.

Classification and treatment of spontaneous carotid-cavernous sinus fistulas.

An anatomical-angiographic classification for carotid-cavernous sinus fistulas is introduced and a series of 14 patients with spontaneous carotid-cavernous sinus fistulas is reviewed to illustrate the usefulness of such a classification for patient evaluation and treatment. Fistulas are divided into four types: Type A are direct high-flow shunts between the internal carotid artery and the cavernous sinus; Type B are dural shunts between meningeal branches of the internal carotid artery and the cavernous sinus; Type C are dural shunts between meningeal branches of the external carotid artery and the cavernous sinus; and Type D are dural shunts between meningeal branches of both the internal and external carotid arteries and the cavernous sinus. The anatomy, clinical manifestations, angiographic evaluation, indications for therapy, and therapeutic options for spontaneous carotid-cavernous sinus fistulas are discussed.

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.

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.

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.

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.