Extraforaminal stenosis in the lumbosacral spine. Efficacy of MR imaging in the coronal plane.

PURPOSE: To review experience with MR images of extraforaminal (EF) stenosis in the lumbosacral spine.

MATERIAL: MR images from 9 patients with 10 EF stenoses were reviewed. The diagnosis was confirmed in 6 patients at surgery, and in 4 on the basis of findings of nerve root injection combined with nerve block.

RESULTS AND

CONCLUSION

All patients had congenital lumbosacral anomalies with various degrees of fixation between the last formed level and the pelvis. In all cases, affected roots were compressed between the transverse process of the last lumbar segment and the sacral ala. MR using coronal plane imaging demonstrated the root impingement directly in the far lateral zone in all patients. However, sagittal and axial images were unable to define the EF stenoses in all patients. The results of this study show that a transitional vertebra is a cause of EF stenosis and that MR images using coronal plane are useful in the assessment of EF stenosis.