Intra-discal vacuum phenomenon with advanced lumbar spine disc degeneration: complementary findings from both MRI and CT

Objective: Intra-Discal Vacuum phenomenon (IDVP) is associated with advanced disc degeneration, representing persistent intra-segmental movement. Our objective is to further characterise IDVP patterns from both MRI and CT thus informing on an otherwise poorly understood phenomenon. Methods: An observational analysis was performed, including an over-60s population sample of 325 lumbar discs in 65 subjects (29 M, 36 F) with low back pain +/- leg symptoms, with MRI of the lumbar spine and concomitant CT abdomen. Exclusion criteria were those with insufficient quality, non-degenerative or destructive spinal pathology, previous neuromodulation or spine instrumentation. Results: 49 subjects (94 levels) displayed IDVP, including 11/184 Pfirrmann grade 3/IVDP positive, 49/79 grade 4/IVDP positive and 34/39 grade 5/IVDP positive discs. Increased severity of IDVP significantly correlated with increased Pfirrmann grade and decreased disc height (p <.05). Affected IDVP levels within the L1L2 & L2L3 region when compared to the L4L5 & L5S1 region, displayed similar Pfirrmann grade (4.1 v 4.3) and disc height (0.52 v 0.51) but with greater severity of IDVP in the latter (1.5 v 1.98, p <.002). While 83/105 (81%) of levels with Pfirrmann 4/5 with reduced disc height, displayed IDVP, a small minority did not, where instead they displayed a significantly higher risk of adjacent IDVP (p <.05). Conclusion: CT and MRI complement each other through the identification of IDVP, allowing the diagnostician further insight on disc degeneration. Worsening severity of IDVP on CT correlates with increased disc degeneration and reduced disc height on MRI, particularly in the lower lumbar spine. A small minority of advanced degenerate discs do not display IDVP and quiesce, mostly where there is presence of an adjacent IDVP. Clinical trial number: Not applicable.