Dynamic Spinal Stenosis in Intradiscal Vacuum Phenomenon: Insights from Standing Weight Bearing CT Myelography.

Low back pain and degenerative disc disease are common causes of spinal canal stenosis, yet conventional supine imaging may underestimate pathology evident under physiologic loading. The intradiscal vacuum phenomenon (IVP), a marker of disc degeneration, has unclear dynamic mechanical implications. We describe a combined standing and recumbent CT myelography technique, demonstrating that while supine imaging shows degenerative changes with IVP, upright cone-beam CT reveals disc space collapse, increased posterior disc bulge, and more severe canal narrowing. In these three illustrative cases, standing CT myelography depicted dynamic disc-space collapse, increased posterior disc bulge, and canal narrowing that were less evident on supine imaging. These observations are hypothesis-generating; prospective studies are needed to determine whether IVP, with or without endplate sclerosis, predicts dynamic interspace collapse.