#445 A Feasibility Study Using Diffusion-weighted Magnetic Resonance (DW-MR) Neurographyof the Lumbar Plexus in the Preoperative Planning of Lateral Access Lumbar Surgery

General Session: Cutting Edge Technology - Imaging Guidance

Presented by: C. Menezes

Author(s):

C.M. Menezes (1)
L.M. Andrade (2)

(1) Lifecenter Hospital, Spine Surgery, Belo Horizonte, Brazil
(2) Axial Centro de Imagens, Radiology, Belo Horizonte, Brazil

Abstract

Introduction: 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 L45 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 plexuz, DW-MR may improve the safety profile of lateral access procedures.

Methods: Seventeen patients (34 sides) with degenerative spine disorders and history of low back pain underwent a DW-MR 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 thisposition was confirmed in sagittal planes.

Results: In all subjects the plexus was successfully mapped. At L3/4, all 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 15(88%) of plexa in zone 4 on the right vs 14 (82%) on the left. At the superior third of L5, the plexus was found in zone 3 in 7 (41%) and 6 (35%), respectively.

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