Separations between the annular fibers or between the annular fibers and their attachments to the vertebral body. These appear as linear foci of hyperintensity on T2-weighted and short tau inversion recovery (STIR) sequences (ie, high-signal-intensity zone). Disk degeneration includes desiccation, mucinous degeneration of the annulus, and fibrosis, which appears as low signal on T2-weighted sequences with varying grades of obscuration of the nucleus pulposus and annulus margins 1).
1)
Pfirrmann CW, Metzdorf A, Zanetti M, Hodler J, Boos N. Magnetic resonance classification of lumbar intervertebral disc degeneration. Spine (Phila Pa 1976). 2001;26(17):1873–1878.