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Myelography was performed in 16 monkeys using either metrizamide or iohexol, a new nonionic aqueous contrast medium. Eight of the animals received almost five times the recommended clinical dose of contrast medium per unit of body weight; the other eight received the equivalent of a high clinical dose. The severity of resultant arachnoiditis 12 weeks later was evaluated by repeat myelography and by histologic study of the arachnoid. No animals had severe arachnoiditis. Two of the four animals examined with the higher dose of metrizamide had moderate arachnoiditis and one had mild arachnoiditis; with the lower dose of metrizamide, two of four animals had mild arachnoiditis. No significant evidence of arachnoiditis was seen in any of the eight animals examined with iohexol.

CT images and anatomic slices of two brains containing numerous demyelinated plaques were correlated. Demyelinated plaques smaller than 0.7 cm were not detected by CT. Some larger plaques were misinterpreted as normal structures. These and other considerations suggest that chronic cerebral demyelination cannot be excluded by negative nonenhanced CT scan.

The computed tomographic (CT) appearance of unfused ossicles in the lumbar spine has had little attention. Unfused ossicles result from accessory ossification centers near the tip of the vertebral processes. Their main importance lies in distinguishing them from fractures. The CT appearance of unfused ossicles in the lumbar spine was correlated with that of the corresponding surface anatomy from a cadaver specimen. Thereafter, 100 consecutive CT studies were reviewed and two cases of presumedly unfused ossicles were found. The CT appearance of unfused ossicles and their differential diagnosis is discussed.

Clinical tolerance to the myelographic contrast media metrizamide and iopamidol was evaluated in 26 and 30 patients, respectively, with a battery of neuropsychologic tests before and after myelography in a randomized, double-blind prospective study. Twenty hospitalized patients with chronic back pain were also studied before and after computed tomography to serve as controls relative to the groups administered contrast agents. Measures of conceptual reasoning and affect were sensitive tests of adverse reactions. These paralleled the incidence of somatic reactions and correlated with the dose of contrast medium. Methodologic problems included varying intervals between myelography and psychometric evaluation among subjects and use of a less-than-ideal control group. Neuropsychologic tests appear to be sensitive for detection of subtle adverse reactions and possibly predictive of their occurrence. Iopamidol was tolerated better than metrizamide, with somatic side effects occurring in 38% of patients receiving metrizamide and in 17% of patients receiving iopamidol.

The spines of 28 cadavers were studied with magnetic resonance (MR) imaging, correlated with anatomic sections, to characterize the progressive and regressive changes in the nucleus pulposus. Four additional types of nucleus pulposus were identified in this study. The transitional type (type II) of childhood had fibrous tissue that developed near the anulus fibrosus anteriorly or posteriorly. MR images showed a notch of reduced signal intensity in the nucleus pulposus where the fiber was developing. The adult type (type III), which is predominant after age 30 years, had an indistinct boundary between the nucleus pulposus and anulus fibrosus. MR images showed the fibrocartilage in the nucleus pulposus and inner anulus fibrosus as areas of high signal intensity. Adult disks with a tear of the anulus fibrosus (type IIIB) had a lower signal intensity on MR images and slightly reduced disk heights. This type may represent an early stage of degeneration. Degenerated intervertebral disks (type IV) had either dense disorganized fibrous tissue or fluid replacing the normal fibrocartilaginous structure of the nucleus pulposus. MR images showed narrow intervertebral disk spaces with either reduced signal intensity if collagen was present or increased signal intensity if fluid was present. This study suggests that the nucleus pulposus may progress normally through types I, II, and III.

Truncation artifacts occur in MR imaging because Fourier transforms are used to process MR signal data. These artifacts may alter the intensity, shape, and anatomic detail of structures in the spine. Ring artifacts (Gibb phenomenon) occurring near highly contrasting interfaces represent but one manifestation of truncation artifacts visible on MR images. We review truncation phenomena by providing graphic and phantom models. Ways in which truncation artifacts alter the MR appearance of the spine are discussed. We found that truncation phenomena are reduced most effectively by using a 256 x 256 matrix whenever feasible.

To correlate the MR appearance of the disk with its fibrous structure, we studied the lumbar intervertebral disks in 10 cadavers with MR, CT, cryomicrotome anatomic sections, and, in selected disks, with histologic and dried sections. In MR images the predominantly fibrous tissues such as Sharpey's fibers had a low signal intensity while the fibrocartilagenous tissues with a mucoid matrix in the intervertebral disk had a high signal intensity. In the equator of the adult disk was a well-defined fibrous plate that contained collagenous, elastic, and reticular fibers with little ground substance. This plate appeared to develop progressively from the periphery of the nucleus toward the center, starting in the second decade of life. The fibrous plate was also distinguished as a lower signal intensity in the MR images.

A detailed analysis of the coronal anatomic and CT appearances of the orbital apex is presented. In cadavers, coronal CT 9800 scans of the orbital apex and precisely corresponding cryomicrotomic sections were obtained. The CT appearance of the optic nerve, anulus of Zinn, and cranial nerves III-VI at the superior orbital fissure and orbital apex were determined. These anatomic structures were also demonstrated in clinical CT studies. Practical applications of the anatomic landmarks in evaluating orbital apex tumors are illustrated.

A case of bilateral clefts in the pedicles of the L1 vertebra, diagnosed by computed tomography, is presented. The differentiation from other clefts located laterally in the neural arch is briefly summarized, and the possible origin of this entity is discussed. It is improbable that the clefts represent persistent neurocentral synchondroses.

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.

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.

The role of contrast medium osmolality in postmyelographic arachnoiditis was studied. Monkeys were injected intrathecally with isotonic saline (290 mOs/kg), hypertonic saline (1,449 mOs/kg), metrizamide (456 or 300 mOs/kg), or methylglucamine iocarnate (1,049 mOs/kg). After 12 weeks the animals were examined for evidence of arachnoiditis, with myelography just prior to sacrifice and microscopic examination of the excised dural sac and its contents. Intrathecal injections of methyglucamine iocarmate or metrizamide caused arachnoiditis while saline did not. Only one animal given 170 mg l/ml (300 mOs/kg) exhibited a more severe reaction than the controls. An increase in the cerebrospinal fluid osmolality alone does not cause arachnoiditis.

MR imaging after IV gadolinium-DTPA administration has demonstrated contrast enhancement in traumatized lumbar intervertebral disks. To characterize the morbid anatomy that correlates with the contrast enhancement, we developed a canine model of traumatized intervertebral disks. Diskectomy was performed with a nucleotome and the spines were imaged biweekly with MR and Gd-DTPA. The spines were studied at necropsy, and their anatomic abnormalities correlated with contrast enhancement detected by MR imaging. Our preliminary results indicate that contrast enhancement occurs where granulation tissue develops in traumatized intervertebral disks.

Metrizamide is a nonionic water-soluble contrast medium for neuroradiological studies that is less irritating to the nervous system than other water-soluble agents. Studies in adults have shown that metrizamide has advantages over currently available media, but experience with children has been limited. Sixty-two children have had myelography or ventriculography using metrizamide. The children ranged in age from 11 days to 22 years. Technically satisfactory studies were obtained in every patient. No major complications were encountered. Minor side-effects included headache in 11 children (18%), mild nausea or vomiting in 16 children (26%), and fever in 4 children (6%). Seizures did not occur. One infant in the study subsequently died of unrelated problems; there was no evidence of arachnoiditis at postmortem examination. Metrizamide is a safe, effective contrast medium for neuroradiological use in children.

Artifacts that can distort the appearance of the cervical spinal cord are caused by data truncation during MR image reconstruction. We used a phantom and then correlated anatomic sections with MR images in cadavers and normal volunteers to evaluate the effect of truncation artifacts on the MR appearance of the spinal cord. When truncation artifacts are minimized, the gray matter and major white-matter columns in the cervical cord can be recognized. T2-weighted gradient-echo MR techniques can best differentiate gray from white matter.

This article describes the CT and MR appearance of the orbital apex and masses in this region. The sectional anatomy by axial, coronal, and sagittal planes as well as the thin-layer technique used to accomplish this is detailed first. Then the application of these techniques to the presence of tumors is illustrated and discussed.

The incidence of unfused ossicles in the lumbar spine, in radiographic studies, is 0.7-1.5%. With a sledge cryomicrotome, we sectioned 273 lumbar facet joints in 38 adult cadavers and correlated the anatomic appearance of the joints with CT and magnetic resonance (MR) images. Ossicles were present in 13% of the cadavers and 2.6% of the facet joints and were demonstrated effectively by MR. The incidence of ossicles, which can be confused with fractures, in the facet joints is higher than previously reported.

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.

The computed tomographic (CT) appearance of the occipito-atlantoaxial articulations and ligaments was analyzed using the CT/T 8800 and 9800 scanners with and without intravenous or intrathecal contrast media. Osseous and ligamentous structures in dissected or sectioned anatomic specimens were correlated with structures seen on the CT images, and the articulations and transverse, alar, and apical ligaments were identified. It is concluded that such an analysis, which has not been done in detail previously, should facilitate the diagnosis of cervical soft-tissue injuries and abnormalities.

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.