Correlation between vacuum phenomenon on CT and fluid on MRI in degenerative disks

The purpose of this study is to correlate the presence of intradiscal vacuum phenomenon on CT to that of intradiscal fluid on MRI.

In a prospective study, 20 patients with lumbar vacuum phenomenon on CT underwent two MRI examinations. One was performed after mobilization, and the other was performed after 6 hours of bed rest. T2-weighted turbo-spin echo (TSE), STIR, T1-weighted TSE, and four consecutive T2-weighted TSE sequences were performed on a 1.5-T scanner. Ninety-five discal segments were assessed for the presence of intradiscal fluid or hyperintense signal on the T2-weighted MRI examinations and were correlated with the presence of vacuum phenomenon on CT, degenerative endplate abnormalities on CT, and edema on MRI.

Sixty-nine of 95 discal segments (72.6%) showed vacuum phenomenon on CT. Sixteen of those 69 discal segments (23.1%) showed intradiscal fluid (n = 12) or hyperintense signal (n = 4) on MRI examinations performed after mobilization. Forty-one of 69 discal segments (59.4%) with vacuum phenomenon showed intradiscal fluid (n = 29) or hyperintense signal (n = 12) on MRI examinations performed after bed rest. Seventeen segments showed only fluid after bed rest. Nine segments showed more fluid after bed rest than after mobilization. Three segments showed an unchanged amount of fluid. There was a significant correlation between the presence of intradiscal fluid and the amount of bone marrow edema on MRI and the presence of degenerative endplate abnormalities on CT, respectively.

The replacement of intradiscal vacuum phenomenon by intradiscal fluid is a time- and position-dependent dynamic process and is related to Modic type 1 degenerative disk disease and degenerative endplate changes.