Shiwei Yu

Progressive and regressive changes in the nucleus pulposus. Part II. The adult.

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.

Incidence of unfused ossicles in the lumbar facet joints: CT, MR, and cryomicrotomy study.

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.

The effect of patient positioning on MR imaging of the internal auditory canal

SummaryIdentification of individual cranial nerves and complete exclusion of tumor in the internal auditory canal may be difficult with MR, especially in imperfectly positioned patients. MR studies of the temporal bones in patients and in normal volunteers positioned non-rotated or canted were correlated with corresponding cryomicrotomic sections. Especially in axial images, oblique sectioning of cranial nerves VII and VIII may cause difficulty in identifying individual nerves. A combination of axial and coronal short TR and TE images can be used to confidently exclude intracanalicular tumor in most cases.

Computerized tomography and biomechanics of lumbar discs

Ruptures or tears of the annulus fibers of the intervertebral disk have been implicated in low-back pain and are common characteristics of degenerated disks. There are differences in the biomechanical properties of normal and degenerated disks, but few studies have addressed differences in degree of degeneration. Several distinct types of annular tears have been described clinically and can be identified on routine computed tomography (CT) and MRI scans. Although annulus tears are thought to generate spinal instability, biomechanical quantification of the different types of tears needs to be completed. The biomechanical characteristics of lumbar intervertebral disks are delineated.<<ETX>>