Fig. 1

MRI tracing for quantitative measures of disc height and disc signal intensity. The shaded region represents the area of the disc. Disc area was defined by using the freehand region of interest measurement tool and tracing around the disc starting along the anterior longitudinal ligament, moving along the superior disc-vertebral interface, posterior longitudinal ligament and finally inferior disc-vertebral interface. Raw disc height was measured by dividing the disc area by length of horizontal line between anterior and posterior boundaries of intervertebral disc. The elliptical region represents the cerebrospinal fluid reference sample