Abstract
Objective To investigate the use of muscle MRI for the differential diagnosis and as a disease progression biomarker for 2 major forms of motor neuron disorders: spinal bulbar muscular atrophy (SBMA) and amyotrophic lateral sclerosis (ALS).
Methods We applied quantitative 3-point Dixon and semiquantitative T1-weighted and short tau inversion recovery (STIR) imaging to bulbar and lower limb muscles and performed clinical and functional assessments in ALS (n = 21) and SBMA (n = 21), alongside healthy controls (n = 16). Acquired images were analyzed for the presence of fat infiltration or edema as well as specific patterns of muscle involvement. Quantitative MRI measurements were correlated with clinical measures of disease severity in ALS and SBMA.
Results Quantitative imaging revealed significant fat infiltration in bulbar (p < 0.001) and limb muscles in SBMA compared to controls (thigh: p < 0.001; calf: p = 0.001), identifying a characteristic pattern of muscle involvement. In ALS, semiquantitative STIR imaging detected marked hyperintensities in lower limb muscles, distinguishing ALS from SBMA and controls. Finally, MRI measurements correlated significantly with clinical scales of disease severity in both ALS and SBMA.
Conclusions Our findings show that muscle MRI differentiates between SBMA and ALS and correlates with disease severity, supporting its use as a diagnostic tool and biomarker for disease progression. This highlights the clinical utility of muscle MRI in motor neuron disorders and contributes to establish objective outcome measures, which is crucial for the development of new drugs.
Glossary
- ALS=
- amyotrophic lateral sclerosis;
- ALSFRS-R=
- ALS Functional Rating Scale–Revised;
- AMAT=
- adult myopathy assessment tool;
- AR=
- androgen receptor;
- BFP=
- biceps femoris posterior;
- CMC=
- calf muscle compartments;
- CSA=
- cross-sectional area;
- FFall=
- overall mean muscle fat fraction;
- FFmsc=
- mean muscle-specific fat fraction;
- fRMAmsc=
- functional remaining muscle area;
- GG=
- genioglossus;
- GH=
- geniohyoideus;
- HG=
- hyoglossus;
- IQR=
- interquartile range;
- LG=
- gastrocnemius lateralis;
- LL=
- lower limb;
- LMN=
- lower motor neuron;
- MG=
- gastrocnemius medialis;
- MH=
- mylohyoideus;
- MND=
- motor neuron disease;
- PL=
- peroneus longus;
- RF=
- rectus femoris;
- SBMA=
- spinal bulbar muscular atrophy;
- SBMA-FRS=
- SBMA Functional Rating Scale;
- SM=
- semimembranosus;
- SO=
- soleus;
- ST=
- semitendinosus;
- STIR=
- short tau inversion recovery;
- TA=
- tibialis anterior;
- TMC=
- thigh muscle compartment;
- TP=
- tibialis posterior;
- VI=
- vastus intermedius;
- VL=
- vastus lateralis
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.
The Article Processing Charge was funded by MRC.
- Received December 5, 2018.
- Accepted in final form April 5, 2019.
- Copyright © 2019 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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