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Abstract
Objective To detect, localize, and quantify peripheral nerve lesions in amyloid light chain (AL) amyloidosis by magnetic resonance neurography (MRN) in correlation with clinical and electrophysiologic findings.
Methods We prospectively examined 20 patients with AL-polyneuropathy (PNP) and 25 age- and sex-matched healthy volunteers. After detailed neurologic and electrophysiologic testing, the patient group was subdivided into mild and moderate PNP. MRN in a 3.0 tesla scanner with anatomical coverage from the lumbosacral plexus and proximal thigh down to the tibiotalar joint was performed by using T2-weighted and dual-echo 2-dimensional sequences with spectral fat saturation and a 3-dimensional, T2-weighted inversion recovery sequence. Besides evaluation of nerve T2-weighted signal, detailed quantification of nerve injury by morphometric (nerve caliber) and microstructural MRN markers (proton spin density, T2 relaxation time) was conducted.
Results Nerve T2-weighted signal increase correlated with disease severity: moderate (420.2 ± 60.1) vs mild AL-PNP (307.2 ± 17.9; p = 0.0003) vs controls (207.0 ± 6.4; p < 0.0001). Proton spin density was also higher in moderate (tibial: 525.5 ± 53.0; peroneal: 553.6 ± 64.5; sural: 492.0 ± 56.6) and mild AL-PNP (tibial: 431.6 ± 22.0; peroneal: 457.6 ± 21.7; sural: 404.8 ± 25.2) vs controls (tibial: 310.5 ± 14.1; peroneal: 313.6 ± 11.6; sural: 261.7 ± 11.0; p < 0.0001 for all nerves). T2 relaxation time was elevated in moderate AL-PNP only (tibial: p = 0.0106; peroneal: p = 0.0070; sural: p = 0.0190). Tibial nerve caliber was higher in moderate (58.0 ± 8.8 mm3) vs mild AL-PNP (46.5 ± 2.5 mm3; p = 0.008) vs controls (39.1 ± 1.2 mm3; p < 0.0001).
Conclusions MRN detects and quantifies peripheral nerve injury in AL-PNP in vivo with high sensitivity and in close correlation with the clinical stage. Quantitative parameters are feasible new imaging biomarkers for the detection of early AL-PNP and might help to monitor microstructural nerve tissue changes under treatment.
Glossary
- AL=
- amyloid light chain;
- ANOVA=
- analysis of variance;
- FoV=
- field of view;
- hATTR=
- hereditary transthyretin amyloidosis;
- MRN=
- magnetic resonance neurography;
- NCS=
- nerve conduction study;
- NIS-LL=
- Neuropathy Impairment Score in the Lower Limbs;
- PNP=
- polyneuropathy;
- PNS=
- peripheral nervous system;
- ρ=
- proton spin density;
- SN=
- spinal nerve;
- T2app=
- apparent T2 relaxation time;
- TE=
- echo time;
- TR=
- repetition time;
- T2w=
- T2-weighted
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received February 6, 2018.
- Accepted in final form May 16, 2018.
- © 2018 American Academy of Neurology
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