Quantitative assessment of sciatic nerve changes in Charcot–Marie–Tooth type 1A patients using magnetic resonance neurography

Abstract

Background and purpose Nerve tissue alterations have rarely been quantified in Charcot–Marie–Tooth type 1A (CMT1A) patients. The aim of the present study was to quantitatively assess the magnetic resonance imaging (MRI) anomalies of the sciatic and tibial nerves in CMT1A disease using quantitative neurography MRI. It was also intended to seek for correlations with clinical variables. Methods Quantitative neurography MRI was used in order to assess differences in nerve volume, proton density and magnetization transfer ratio in the lower limbs of CMT1A patients and healthy controls. Disease severity was evaluated using the Charcot–Marie–Tooth Neuropathy Score version 2, Charcot–Marie–Tooth examination scores and Overall Neuropathy Limitations Scale scores. Electrophysiological measurements were performed in order to assess the compound motor action potential and the Motor Unit Number Index. Clinical impairment was evaluated using muscle strength measurements and Charcot–Marie–Tooth examination scores. Results A total of 32 CMT1A patients were enrolled and compared to 13 healthy subjects. The 3D nerve volume, magnetization transfer ratio and proton density were significantly different in CMT1A patients for the whole sciatic and tibial nerve volume. The sciatic nerve volume was significantly correlated with the whole set of clinical scores whereas no correlation was found between the tibial nerve volume and the clinical scores. Conclusion Nerve injury could be quantified in vivo using quantitative neurography MRI and the corresponding biomarkers were correlated with clinical disability in CMT1A patients. The sensitivity of the selected metrics will have to be assessed through repeated measurements over time during longitudinal studies to evaluate structural nerve changes under treatment.

Reliability and reproducibility of sciatic nerve magnetization transfer imaging and T2 relaxometry

“…5 Bland-Altman plots for assessment of interreader reliability of magnetization transfer ratio (MTR) (a), transverse relaxation time T2 (b), and proton spin density (PSD) (c) of the sciatic nerve. The black continuous line represents the mean of all differences (bias), grey dotted lines show the 95% limits of agreement from 3.4 to 13%, and in three out of four studies a difference of over 4.7% was observed (Table 4) [11,12,14,24]. Notably, the mean MTR of our cohort was lower than in most of the control groups listed in Table 4.…”

“…The examined cohort was male, however, we would not expect different results for female participants, since all parameters have been shown to not systematically differ between sexes [33,41]. Furthermore, planning of the MR examination and image postprocessing were performed by experienced neuromuscular radiologists, and also for this reason the proposed orientational values should rather be [11,12,53]. To reduce the effects of B1 field inhomogeneities on the received signal, we applied an adaptive inline image filter and restricted analysis to six central slices where the B1 field is expected to be more homogeneous than at the edges of the slab.…”

“…These techniques offer additional information about nerve microstructure or tissue composition and provide quantitative biomarkers. In addition to DTI-which has been well evaluated [10]-T2 relaxometry and magnetization transfer imaging (MTI) have increasingly been applied as novel quantitative MRN techniques in recent investigations [11][12][13][14].…”

Intraepineurial Fat Quantification and Cross-sectional Area Analysis of the Sciatic Nerve Using MRI in Charcot-Marie-Tooth Disease Type 1A Patients

“…Recently, MRI with various up-to-date imaging techniques has been applied to neuromuscular evaluation and attempts to derive potential imaging biomarkers for CMT1A patients. [17][18][19][20] Among them, Dixon MRI is an imaging technique increasingly used for fat fraction (FF) measurement. It has proved to be highly sensitive and reproducible for evaluating disease progression in the skeletal muscles of neuromuscular disorder patients.…”

Intraepineurial fat quantification and cross-sectional area analysis of the sciatic nerve using MRI in Charcot-Marie-Tooth disease type 1A patients

“…Recently, MRI with various up-to-date imaging techniques has been applied to neuromuscular evaluation and attempts to derive potential imaging biomarkers for CMT1A patients 17 – 20 . Among them, Dixon MRI is an imaging technique increasingly used for fat fraction (FF) measurement.…”