Three-Dimensional Magnetic Resonance Rendering Imaging of Lumbosacral Radiculography in the Diagnosis of Symptomatic Extraforaminal Disc Herniation With or Without Foraminal Extension

STUDY DESIGN: Retrospective analysis of lumbosacral radiculography using 3-dimensional (3D) magnetic resonance (MR) rendering in patients with extraforaminal disc herniation. OBJECTIVE: To investigate the significance of lumbosacral radiculography as depicted by 3D MR rendering in the diagnosis of symptomatic extraforaminal disc herniation with or without foraminal extension. SUMMARY OF BACKGROUND DATA: Given that accurate evaluation of the extraforaminal zones on routine axial and sagittal images is difficult, extraforaminal disc herniations tend to be sometimes overlooked. In addition, oblique coronal images along intervertebral foramina and MR myelography may not clearly demonstrate a detailed full view of nerve root changes. Furthermore, the detection of the morphologic changes of the nerve root is very important for the diagnosis of symptomatic extraforaminal disc herniation. Thus, a useful method for evaluating the nerve root in order to diagnose symptomatic extraforaminal disc herniation is required. METHODS: Twenty-four patients with extraforaminal and combined (extraforaminal with foraminal) lumbar disc herniations were included in this study. Conventional spin-echo sequence and 3D coronal fast-field echo sequences with selective water excitation by using the principles of the selective excitation technique (Proset imaging) were acquired. Indentation and swelling of the nerve roots and dorsal root ganglion (DRG) in the symptomatic sides and levels were evaluated on the basis of 3D MR rendering images of the lumbar spine. The tilting angle of the nerve root in the symptomatic side was compared with those in the asymptomatic contralateral side again on the basis of the 3D MR rendering images. RESULTS: Dorsal root ganglion indentation without swelling of the nerve roots was found in 7 patients whereas that with swelling of the nerve roots was observed in 6 patients. Swelling of the entire segment of the nerve from nerve root to spinal nerve (n = 9) or only the spinal nerve (n = 2) was observed in 11 patients. Compared with the contralateral nerve root, 7 patients exhibited a tilting angle abnormality of the ipsilateral nerve root. CONCLUSION: Based on lumbosacral radiculography through 3D MR rendering, important findings related to the diagnosis of symptomatic extraforaminal disc herniation include swelling of DRG and/or nerve roots and DRG indentation. Ultimately, 3D MR lumbosacral radiculography is a very useful method in the diagnosis of the symptomatic extraforaminal disc herniation.