T2 mapping of the distal sciatic nerve in healthy subjects and patients suffering from lumbar disc herniation with nerve compression

Nico Sollmann,Dominik Weidlich,Elisabeth Klupp,Barbara Cervantes,Dimitrios C Karampinos,Claus Zimmer,Thomas Baum,Jan S Kirschke,Carl Ganter,Ernst J Rummeny

doi:10.1007/s10334-020-00832-w

Abstract

ObjectiveTo measure T2 values for magnetic resonance neurography (MRN) of the healthy distal sciatic nerve and compare those to T2 changes in patients with nerve compression.Materials and methodsTwenty-one healthy subjects and five patients with sciatica due to disc herniation underwent MRN using a T2-prepared turbo spin echo (TSE) sequence of the distal sciatic nerve bilaterally. Six and one of those healthy subjects further underwent a commonly used multi-echo spin-echo (MESE) sequence and magnetic resonance spectroscopy (MRS), respectively.ResultsT2 values derived from the T2-prepared TSE sequence were 44.6 ± 3.0 ms (left) and 44.5 ± 2.6 ms (right) in healthy subjects and showed good inter-reader reliability. In patients, T2 values of 61.5 ± 6.2 ms (affected side) versus 43.3 ± 2.4 ms (unaffected side) were obtained. T2 values of MRS were in good agreement with measurements from the T2-prepared TSE, but not with those of the MESE sequence.DiscussionA T2-prepared TSE sequence enables precise determination of T2 values of the distal sciatic nerve in agreement with MRS. A MESE sequence tends to overestimate nerve T2 compared to T2 from MRS due to the influence of residual fat on T2 quantification. Our approach may enable to quantitatively assess direct nerve affection related to nerve compression.

Highlights

Magnetic resonance neurography (MRN) of the peripheral nervous system (PNS), the application of magnetic resonance imaging (MRI) for the depiction and study of peripheral nerves of the human body, is increasingly applied in vivo
We propose that patients with nerve compression at the level of the lumbosacral plexus (LSP) present with unilaterally elevated T2 values of the distal sciatic nerve when compared to the unaffected side or healthy subjects, probably due to edematous changes or swelling of nerves related to proximal compressive effects
A more commonly used 2D multi-echo spin-echo (MESE) sequence showed higher T2 values for the distal sciatic nerve of around 63 ms; data derived from magnetic resonance spectroscopy (MRS) were in accordance with the T2 values derived from the 3D T2-prepared turbo spin echo (TSE) sequence

Summary

Introduction

Magnetic resonance neurography (MRN) of the peripheral nervous system (PNS), the application of magnetic resonance imaging (MRI) for the depiction and study of peripheral nerves of the human body, is increasingly applied in vivo. Further data on physiological T2 values and systematic evaluations of reliability are highly needed for a more profound understanding of T2 values of the sciatic nerve, paving the way to identify valid biomarkers in quantitative MRN of the PNS Against this background, the objective of the present study is (1) to provide T2 values for the healthy distal sciatic nerve and to evaluate reliability of quantitative MRN by T2 mapping in healthy subjects, (2) to compare our novel T2 mapping approach against T2 measurements in a commonly used MESE sequence (having nerve-water T2 from MRS as the reference standard), and (3) to evaluate potential alterations in T2 values of the distal sciatic nerve due to degenerative disc disease with nerve compression at the level of the LSP in patients suffering from unilateral sciatica. We propose that patients with nerve compression at the level of the LSP present with unilaterally elevated T2 values of the distal sciatic nerve when compared to the unaffected side or healthy subjects, probably due to edematous changes or swelling of nerves related to proximal compressive effects

Materials and methods

Discussion

Findings

Compliance with ethical standards