Research article
MR neurography of lumbosacral nerve roots: Diagnostic value in chronic inflammatory demyelinating polyradiculoneuropathy and correlation with electrophysiological parameters

https://doi.org/10.1016/j.ejrad.2020.108816Get rights and content

Highlights

  • CIDP patients showed increased size and signal of lumbosacral nerve roots on MRN.

  • Size and signal of L5 and S1 roots correlated with electrophysiological indices.

  • Size of lumbosacral nerve roots had a better value than signal in diagnosing CIDP.

  • Quantification of lumbosacral nerve roots on MRN may serve as a supporting tool.

Abstract

Purpose

MR neurography(MRN) is an advanced imaging technique to visualize peripheral nerves. Our aim was to determine the value of morphological features of lumbosacral nerve roots on MRN in diagnosing chronic inflammatory demyelinating polyradiculoneuropathy(CIDP) and analyze their correlations with electrophysiological parameters.

Methods

MRN of lumbosacral plexus was performed in 21 CIDP patients and 21 healthy volunteers. The cross-sectional areas(CSAs) and signal intensities(SI) of L3 to S1 nerve roots were measured and compared between two groups. Receiver operating characteristic(ROC) curves were plotted to assess the diagnostic accuracy. All patients also underwent nerve conduction studies. Correlations between CSAs and SI of lumbosacral nerve roots and electrophysiological parameters were analyzed.

Results

Compared with control group, CIDP patients showed significantly increased CSAs and SI from L3 to S1 nerve root (P < 0.001 and P < 0.05 respectively for all nerve roots). The CSAmean and SImean were 28.04 ± 8.55mm2, 1.314 ± 0.199 for patient group and 14.91 ± 2.36mm2,1.155 ± 0.094 for control group. ROC analysis revealed the best diagnostic accuracy for the CSAmean with an area under the curve of 0.968 and optimal cut-off value of 19.20 mm2. CSAs of L5 or S1 nerve root correlated positively with central latency and negatively with conduction velocity of tibial nerve. SI of L5 also had a positive correlation with latency of sural nerve.

Conclusions

Evaluation of lumbosacral nerve roots on MRN in a quantitative manner may serve as an important tool to support the diagnosis of CIDP.

Introduction

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is the most common immune-mediated inflammatory polyneuropathy, which is typically characterized by symmetrical involvement and proximal as well as distal muscle weakness [1,2]. The pathological hallmarks of CIDP are demyelination and remyelination [3]. Evidence from postmortem and electrophysiology studies proved that demyelinative lesions initially affected spinal nerve roots, and then extended to nerve trunks and distal nerve segments [[4], [5], [6], [7], [8]]. Clinical treatments for CIDP include intravenous immunoglobulin, corticosteroids and plasm exchange. Timely treatment for the CIDP patients requires early and accurate diagnosis by evaluating proximal spinal nerve roots, which is crucial to rescue patients in early stages and prevent secondary axon injury [2]. However, existing examinations like nerve conduction studies and high-resolution ultrasound are unable to detect abnormalities of spinal nerve roots due to the deep anatomy.

MR neurography(MRN), also known as MR imaging of peripheral Nerves, is an advanced MR technique that can help delineate deep nerves conspicuously and locate lesions accurately. First proposed by Filler in 1992, it combined fat suppression technique and T2-weighted sequence to suppress fat tissue around peripheral nerves and emphasize nerve signal [[9], [10], [11]]. To date, MRN has been widely applied for the diagnosis of various peripheral neuropathies, including entrapment, injury, neoplasm and inflammatory neuropathies such as CIDP [10,[12], [13], [14], [15], [16], [17], [18], [19]]. Previous studies of CIDP mainly focused on the imaging of the brachial plexus and cervical nerve roots, whereas few studies have evaluated morphologic changes in the lumbosacral region [2,20,21]. To the best of our knowledge, lumbosacral nerve roots and cauda equina were reported to be more frequently involved in CIDP patients [5].

Therefore, in this study, we aimed to explore the value of lumbosacral nerve roots on MRN in the diagnosis of CIDP by quantifying cross-sectional areas (CSAs) and signal intensity(SI) of L3 to S1 nerve roots, and to analyze their correlations with electrophysiological parameters of lower extremities.

Section snippets

Subjects

Inclusion criteria: patients who met the diagnostic criteria of CIDP by European Federation of Neurological Societies/Peripheral Nerve Society 2010 from June 2016 to April 2019 from our neuromuscular clinic (n = 34) [22]. Exclusion criteria: a) patients in combination with other peripheral neuropathies, such as Charcot-Marie-Tooth disease type 1A (n = 2) b) patients suffering from severe lumbar disc herniation (n = 7) c) patients with injury (n = 1), neoplasm (n = 0) and operation history (n =

Clinical characteristics

A total of 21 subjects were enrolled in CIDP group including 8 females and 13 males. Their ages ranged from 28 to 67 years old and mean age ± SD was 51.3 ± 14.7 years old. Disease duration at the time of study varied dramatically, ranging from 2 months to 84 months and the median disease duration was 7 months. In CIDP group, one patient was diagnosed as Lewis-Sumner Syndrome and another one as distal acquired demyelinating symmetric neuropathy. All the rest patients met the diagnostic criteria

Discussion

In this study, we quantified the size and signal of L3 to S1 nerve roots in 21 CIDP patients and 21 volunteers with MR Neurography. Compared to healthy controls, CIDP patients exhibited significantly increased cross-sectional areas as well as signal intensity in every single nerve root, which was caused by the proliferation of Schwann cell and the edema in the endoneurium [6,26].

Up to now, few studies have systematically evaluated the morphological features of lumbosacral nerve roots of CIDP

Declaration of Competing Interest

The authors have no conflicts of interest to declare.

Acknowledgments

This work was supported by the National Key Research and Development Plan (Grant No. 2017YFC0112904). We are grateful to Jing Wang for her writing assistance and Kai Qiao for her job in nerve conduction examinations.

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