Atlantoaxial arthrodesis in the presence of posterior spondyloschisis (bifid arch) of the atlas. A report of three cases and an evaluation of alternative wiring techniques by computerized tomography.

The presence of a bifid posterior arch of the atlas has been regarded as a contraindication to the wiring of C1-2 for atlantoaxial arthrodesis. Three cases with C1 posterior spondyloschisis are presented with successful atlantoaxial arthrodesis using laterally placed wires to avoid the midline defect of the atlas. An experimental study of the efficacy of three different wiring constructs by computerized tomography showed that there is little difference between midline versus lateral wiring in restricting rotation of C1-2.

Unusual CT patterns of multiple sclerosis.

In three patients with histologically confirmed, acute demyelinating disease (multiple sclerosis), serial cranial computed tomography revealed unusual findings. Computed tomography showed contrast-enhancing lesions with mass effect, which suggested brain tumors and the need for surgical biopsy. Steroids were administered to each patients; in two, the large mass lesions resolved dramatically. These and other rapid changes may help in the recognition of multiple sclerosis.

Another look at blow-out fractures of the orbit.

Thirty cases of orbital floor blow-out fractures proven by tomography were retrospectively reviewed to determine the accuracy of the plain films. Using the maximum diameter from the tomograms, the area and volume of the fractures were calculated and correlated with the presence of diplopia and enophthalmos at the time of presentation and at subsequent follow-up. Nine of the 30 cases underwent surgical repair. Orbital floor fractures were recognized in 29 of 30 cases using only the 28 degrees Caldwell and Waters views. Routine tomography is unnecessary and should be reserved as a preoperative evaluation in patients with enophthalmos to establish the presence of a significant associated medial wall prolapse.

Blow-out fractures of the orbit: a comparison of computed tomography and conventional radiography with anatomical correlation.

Orbital blow-out fractures were experimentally created in eight human cadavers. Each orbit underwent conventional radiographic studies, complex motion tomography, and computed tomographic examinations. A comparison of the three modalities was made. Anatomical correlation was obtained by dissecting the orbits. The significance of medial-wall fractures and enophthalmos is discussed. Limitation of inferior rectus muscle mobility is thought to be a result of muscle kinking associated with orbital fat-pad prolapse at the fracture site, rather than muscle incarceration. Blow-out fractures should be evaluated by computed tomographic computer reformations in the oblique sagittal plane.

Evaluation of orbital and eye lesions by radiographic examination, ultrasound, and computerized tomography.

This article examines three imaging procedures for the evaluation of orbital and eye lesions. In the radiographic section we discuss the normal anatomy, the projections to show the anatomy, and the interpretation of bone changes caused by benign and malignant lesions. In the next section we describe the equipment employed in the ultrasonic evaluation of the eye and orbit and the principles applied in the diagnosis of lesions of the eye and orbit by ultrasound. We introduce the CT section by explaining the methodology of computerized tomography of the orbit. The criteria for evaluating lesions of the eye and orbit are presented with appropriate cases for illustration. The discussion and summary detail the relative merit of these imaging procedures ad their usefulness in the diagnosis work-up of pathological conditions of the eye and orbit.

Transcatheter fiberoptic laser coagulation of blood vessels.

In ten rabbit ears the central auricular artery was percutaneously catheterized and subjected to doses of laser energy transmitted through a flexible optical fiber within the artery. Arterial occlusion was not produced in the initial three ears using energy levels less than 600 mW. Higher levels of laser energy, in the range of 800-1000 mW, caused arterial coagulation in six of the remaining seven rabbit ears. Serial observations by transillumination of the ears, postmortem angiography, and histologic examination demonstrated complete arterial ablation. The experiments showed that segmental arterial ablation is feasible using an intra-arterial optical fiber to direct laser energy to a specific arterial target. Technical refinements and potential therapeutic application are discussed.

Neurological applications of computed tomography.

Prior to the development of computed tomography, radiographic visualization of the brain and spinal cord relied on the indirect imaging methods of angiography, pneumography, and myelography. Although those invasive techniques still play an important diagnostic role, computed tomography has largely replaced them as the main imaging modality of the brain. Its rapid noninvasive nature heralds a major advance in clinical neurological diagnosis.

Diagnosis of empty sella with CT scan.

The diagnosis of empty sella was made correctly by CT scanning in 100% of 19 cases studied.

Computed tomography of the skull base.

By applying a wide window to computed tomography (CT) images, excellent detail of the skull base has been obtained. This technique has been apllied to lesions involving the sellar, parasellar, sphenoid wing, petrous bone, clival, and foramen magnum regions. Thus, CT has proved to have an additional dimension in the delineation of pathology.

Extra-axial growth of fourth ventricle tumors - angiographic changes.

Tumors of the fourth ventricle, particularly ependymomas, may grow out of the ventricular cavity into the cerebellopontine angle cistern and the subarachnoid cisterns. The angiographic changes will then suggest both the intra- and extraventricular location of the tumors. The ependymoma is the most prone of the fourth ventricle tumors to demonstrate this pattern of growth.