Dilatation of the spinal epidural venous plexus in patients with prominent epidural fat.

Objective: The purpose of this study was to evaluate the correlation between the dilatation of the spinal epidural venous plexus (SEVP) and the amount of epidural fat (EF). Methods: Between January 2007 and January 2012, 116 patients with prominent EF and 116 control subjects without prominent EF were included in this study. On the lumbar MR images, we graded the amount of EF and counted the number of vertebrae to determine the longitudinal extent of the EF. We evaluated and classified the dilatation of the SEVP and the degree of central canal stenosis. Results: SEVP dilatation significantly differed between the group with prominent EF and the control group (p-value < 0.0001). Dilatation of the anterior epidural veins was seen in all subjects with dilatation of the SEVP. In the group with prominent EF, 80 (69%) patients showed dilatation of the posterior epidural veins. The longitudinal extent of the prominent EF was significantly associated with the grade of SEVP dilatation, The EF grade and the sum of the EF grades of all levels of the lumbar spine with prominent EF showed a positive correlation with the grade of central canal stenosis (r=0.421 and r = 0.347, respectively; p-value < 0.0001). Conclusion: The dilatation of epidural veins was statistically significant in patients with prominent EF. The detection of SEVP dilatation on MR images may be helpful for spine surgery involving the epidural space. Advances in knowledge: Owing to the risk of bleeding, the detection of SEVP dilatation on MRI may be helpful when considering decompression surgery with a posterior approach for spinal stenosis caused by prominent EF,