muscular dystrophy Severe paraspinal muscle involvement in facioscapulohumeral

Objective: In this study, involvement of paraspinal muscles in 50 patients with facioscapulohumeral dystrophy (FSHD) was evaluated using MRI. Methods: The Dixon MRI technique was used in this observational study to quantify muscle fat content of paraspinal and leg muscles. Muscle strength in the neck, back, and legs was assessed with a handheld dynamometer. All subjects completed the Low Back Pain Rating Scale questionnaire. MRI findingswere comparedwith 31 age-matched controls and correlated tomuscle strength, back pain, and MRI findings in lower extremities. Results: The fat fraction in muscles was significantly higher in patients with FSHD than in controls: paraspinal fat fraction was 38% in patients vs 20% in controls, thigh fat fraction was 36% vs 11%, and calf fat fraction was 37% vs 11%. Increased paraspinal fat fraction correlated with D4Z4 repeat size, FSHD severity score, fat fraction of the thigh, and muscle strength in the back. The prevalence of back pain was 3 times higher in patients with FSHD vs controls, but back pain did not correlate with the paraspinal fat fraction. Conclusions: This study shows a prominent involvement of paraspinal muscles in patients with FSHD, which should be considered in the management of this condition. Neurology® 2014;83:1–6 GLOSSARY DMD5Duchenne muscular dystrophy; FSHD5 facioscapulohumeral dystrophy; LBPRS5 Low Back Pain Rating Scale; TE5 echo time. Facioscapulohumeral dystrophy (FSHD) is the second most common autosomal dominant muscular dystrophy worldwide with a prevalence of 1:15,000 to 20,000. In most patients, the disease is caused by a deletion of repeats in the D4Z4 gene on chromosome 4q35. FSHD is a progressive disorder characterized by asymmetric muscular wasting and weakness of the face, scapular stabilizers, and proximal arms. However, the clinical presentation varies, and involvement of leg and abdominal muscles is also a common feature. Weakness of the paraspinal muscles has, however, only been reported in few patients with FSHD but has not been investigated systematically in this patient group. It is known that pain is a significant problem for many patients with FSHD, and lower back pain has been found to be the most frequent pain area of patients with FSHD. Chronic back pain in FSHD has been suggested to be exacerbated by the weakness of the abdominal and neck flexor muscles. However, we speculate that weakness of the paraspinal muscles could also exacerbate the lower back pain. To evaluate involvement of the paraspinal muscles in FSHD, we performed Dixon MRI of the back in 50 patients with FSHD.MRI provides a great tool to assess muscle quality in patients with muscular dystrophies whereby affected muscles often show a marked degree of fat infiltration. The quantitative technique is a simple spectroscopic imaging technique for water and fat separation, in which the availability of fat-only images allows for fat fraction analysis. METHODS Standard protocol approvals and patient consents. The Danish National Committee on Health Research Ethics approved the research protocol (approval number: H-3-2012-163) and all subjects gave written and oral consent to participate. From the Neuromuscular Research Unit, Department of Neurology (J.R.D., C.R.V., J.V.) and Department of Diagnostic Radiology (C.T.), Rigshospitalet, University of Copenhagen, Denmark. Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article. © 2014 American Academy of Neurology 1 a 2014 American Academy of Neurology. Unauthorized reproduction of this article is prohibited. Published Ahead of Print on August 20, 2014 as 10.1212/WNL.0000000000000828