The increased signal intensity at the vertebral body endplates after chemonucleolysis demonstrated by magnetic resonance imaging.

Changes in signal intensity observed by magnetic resonance imaging in the contiguous end plates of injected discs after chemonucleolysis over a period of 2 years in 28 patients were evaluated. These changes appeared to be of two types; a transiently increased signal intensity on T2-weighted images, and a progressively increased signal intensity on T1-weighted images with isointense or hyperintense signal on T2-weighted images. The former appeared within three months and disappeared within 2 years. This change was observed in six patients (21%), whose mean age was higher than that of the other patients. This change correlated with the preinjection state of the affected disc. The latter appeared after 2 years and was accompanied by sclerotic changes on roentgenograms. These changes were observed in five patients (18%). The discs, of which the contiguous end plates showed these changes, did not recover the decreased nuclear signal intensity in four patients. These changes are considered to be a sign of degenerative spondylosis in the treated segment.