Diffusion-Weighted Magnetic Resonance (DW-MR) Neurography of the Lumbar Plexus in the Preoperative Planning of Lateral Access Lumbar Surgery

Presented at SMISS Annual Forum 2013
By Cristiano Menezes MD
With William Rodgers MD, FACS, Luciene Andrade MD, Carlos Herrero MD, Helton Defino MD, PhD, Marcos Ferreira Jr. MD, Marcello Nogueira-Barbosa MD, PhD,

Disclosures: Cristiano Menezes MD B; NuVasive, Medtronic. William Rodgers MD, FACS B; NuVasive. D; NuVasive, Alphatec. F; NuVasive., Luciene Andrade MD None, Carlos Herrero MD None, Helton Defino MD, PhD None, Marcos Ferreira Jr. MD None, Marcello Nogueira-Barbosa MD, PhD None,

Background: Lateral access lumbar surgery has rapidly increased in popularity in the last several years. However, the technique remains limited by the risk of injury to the lumbar plexus, most commonly the femoral nerve near the L4L5 level.
While real-time neural monitoring can decrease the incidence of such injuries, postoperative deficits can still occur. The purpose of this study is to introduce and assess DW-MR neurography for imaging of the lumbar plexus in the preoperative planning of lateral access surgery. Magnetic resonance (MR) neurography has been used to evaluate abnormal conditions of entire nerves
and nerve bundles by providing better contrast between the nerves and the surrounding tissues. By providing the surgeon with a preoperative roadmap of the lumbar plexus, DW-MR may improve the safety profile of lateral access procedures.

Methods: Ninety nine patients (188 sides) with degenerative spine disorders and history of low back pain underwent a DWMR examination of the lumbar plexus in relation to the L3L4 and L4L5 disc spaces and superior third of the L5 vertebral body. Images were reconstructed in axial plane using high-resolution 10 mm MIP slabs over the disc space and 22 mm MIP slabs in L3-L4 and L4-L5 interspace to mimic the working zone of standard
lateral access retractors. L4 spinal nerve and femoral nerve position were analyzed relative to the L45 disc and this position was confirmed in sagittal planes.

Results: In all subjects the plexus was successfully mapped. At L3/4, all but one case the components of the plexus (except the genitofemoral nerve) were in zone 4. The L3 and L4 roots coalesced into the femoral nerve below the L4/5 disc space in all subjects. Side to side variation was noted with 81 sides (86,2%) of plexa in zone 4 on the right vs 44 (78,7%) on the left. At the superior third of L5, the plexus was found in zone 3 in 26 sides (27,7%) and 34 (36,2%), respectively; and at zone 2 in 4 (4,3%) on the right and 2 (2,1%) on the left.

Conclusion: DW-MR neurography appears to afford a noninvasive method of mapping the lumbar plexus preoperatively