CT recognition of optic nerve sheath meningioma: abnormal sheath visualization.

Optic nerve sheath meningiomas and optic nerve gliomas can be difficult to differentiate by computed tomography (CT). Three patients with optic nerve sheath meningiomas were studied with a CT/T 8800 scanner with 1.5-mm-thick axial sections and intravenous contrast material. In each case, an abnormal optic nerve sheath was identified by CT. A soft-tissue mass arose from one side of the sheath in one patient, and the entire sheath was enlarged in two patients. This provides a basis for distinguishing optic nerve sheath meningioma from optic nerve glioma.

Detection of demyelinated plaques with xenon-enhanced computed tomography.

Studies of xenon-enhanced CT for detecting cerebral demyelination have produced conflicting results. Therefore, we studied the effect of xenon inhalation on the CT appearance of five demyelinated plaques. The plaques and the surrounding white matter increased commensurately in attenuation during xenon inhalation. Therefore, xenon enhancement does not generally increase the sensitivity of CT for detecting cerebral demyelination.

A clinical evaluation of xenon enhancement for computed tomography.

Xenon increases the attenuation coefficients of tissues in which it dissolves and, therefore, enhances lipid-rich material. The authors evaluated xenon enhancement for computed tomography. Patients and normal subjects were given xenon in subanesthetic concentrations and were scanned in a large aperture CT scanner. Patients tolerated 30-50% inhaled xenon well. Cerebral tissues and lung were enhanced by this concentration of xenon. Xenon inhalation in subanesthetic concentrations will be a useful technique for characterizing abnormal lipid tissues and for estimating cerebral blood flow.

Computed tomography in the diagnosis of herniated nucleus pulposus.

In this study, the effectiveness of computed tomography(CT) in diagnosing herniated nucleus pulposus was evaluated. Sixteen CT examinations which were interpreted as positive for a herniated disk, and were intraoperatively confirmed, were reviewed. In all 16 patients, CT demonstrated posterior protrusion of the disk and displacement of anterior epidural fat. Calcification within the protruding disk was noted in several patients, and an extruded disk fragment identified by CT in two. In all cases, the CT findings correlated closely with the surgical findings. This study suggests that CT accurately demonstrates disk herniation.

Soft-tissue anatomy within the spinal canal as seen on computed tomography.

The CT appearance of the vascular, ligamentous, and neural tissues in the spinal canal was studied in 50 patients and 5 cadavers. In some patients, iodinated contrast medium was first injected into the ascending lumbar veins, nucleus pulposus, or theca. Positive identification of spinal soft tissues on the CT image was made by reference to cadaver dissections. The spinal cord, nerves, root sheaths, retrovertebral plexus, epidural and basivertebral veins, posterior longitudinal ligament and ligamentum flavum, intervertebral disks, and vertebral arteries can be demonstrated by CT, indicating its value in the diagnosis of disease of the cord, disk, and epidural space.

Clinical cerebral blood flow measurement with inhaled xenon and CT.

Cerebral blood flow measurement has not yet been attempted with xenon and CT in patients. Xenon washout was studied in three patients receiving subanesthetic concentrations of xenon. Cerebral enhancement after 30%--50% inhaled xenon was demonstrated without serious side effects. Clinical cerebral blood flow measurements with xenon and CT may be feasible.

Taylor-Haughton line revisited.

In 1900 Taylor and Haughton described a technique to define a line on the scalp directly above the central (rolandic) fissure. The Taylor-Haughton line was used to identify the central fissure in computed tomography (CT) images. Radiopaque catheters are placed on the scalp on either side of the Taylor-Haughton line prior to CT imaging. The accuracy of the Taylor-Haughton line for identifying the central fissure was also investigated in cadaver brains. The Taylor-Haughton line provides a good approximation of the location of the rolandic fissure.

Computed tomography of the lumbar facet joints.

Lumbar facet joints are difficult to image with conventional radiographic techniques. A series of 100 consecutive cases of low back pain and sciatica was examined with CT. Abnormal facet joints were found in 65. Abnormalities demonstrated by CT included osteophyte formation, hypertrophy of articular processes, articular cartilage thinning, vacuum joint phenomenon, and calcification of the joint capsule. In patients with sciatic or low back pain, CT is indicated to demonstrate treatable abnormalities of the facet joints.

The computed tomographic appearance of the normal pituitary gland and pituitary microadenomas.

With the use of axial and coronal computed tomography (CT), the authors compared the density, contrast enhancement, and dimensions of normal pituitary glands and pituitary microadenomas. The normal gland appears homogeneous, nearly isodense with brain tissue, and it enhances uniformly. Its upper surface is concave downward or flat and its height 2-7 mm. The cavernous sinuses, the third, fourth, and sixth cranial nerves, the infundibulum, and the adjacent carotid arteries are well demonstrated by CT. Abnormal height and upward convexity of the gland are reliable signs of prolactinoma; abnormal density and enhancement are suggestive signs. CT findings in prolactin- and ACTH-secreting tumors may differ. CT is more sensitive and more specific than polytomography in the diagnosis of pituitary adenoma.

The reliability of computer tomography for the diagnosis and differential diagnosis of meningiomas, gliomas, and brain metastases.

The CT characteristics were studied in a series of 90 tumours, and the diagnostic criteria were determined for meningiomas glioblastomas, other gliomas and metastases. These criteria were then employed in another group of 46 tumours in which the histological diagnosis was not known at the time of examination. The over-all diagnostic accuracy was 85%, and it was largely the same for the various sub-groups. Careful combination of the CT characteristics, perfect techniques, and increased experience may further improve the diagnostic accuracy.