P.180Paraspinal muscle affection in limb-girdle muscular dystrophy type 2I patients

Abstract

The autosomal recessive limb-girdle muscular dystrophy type 2I (LGMD2I) is characterized by progressive weakness of shoulder- and hip-girdles. Affection of the proximal extremity muscles is well-described whereas description of paraspinal muscle involvement is lacking. In this study, we investigate the involvement of paraspinal muscles in patients with LGMD2I. We used quantitative MRI (Dixon technique) to investigate fat replacement in leg and paraspinal muscles: erector spinae at C6, Th12 and L4/L5 and multifidus at Th12 and L4/L5. Back strength was measured by Biodex stationary dynamometry. The study plans to include 20 LGMD2I patients and 24 matched healthy controls (HC). Currently, 10 LGMD2I patients (mean age 37.6 (range 19-60), M:F=6:4) and 24 HC (mean age 41 (25-62), M:F=12:8) have been studied. MRI has been performed in all LGMD2I patients and 20 HC. Stationary dynamometry was done in all LGMD2I patients and 11 HC. LGMD2I patients have a significantly increased mean fat fraction (mFF) in paraspinal muscles. At cervical level: mFF is 29.9% vs 14.3% in HC (p=0.00017), thoracic level: 32.8% vs 8.7% (p=4.5•10-6), and lumbar level: 58.8% vs 24.6% (p=3.02•10-6). The psoas major muscle was also severely affected with a mFF of 54.8% vs 9.3% in HC (p=5.2•10-8). In the legs, especially the hamstrings have increased mFF (53.2% vs 9.4% (p=2.6•10-8)). Data shows a tendency of reduced back strength with increased mFF. Mean trunk extension peak torque is 96.6 Nm vs 296.9 Nm in HC (p=2.1•10-6). In conclusion, the results suggest that patients with LGMD2I have affection of the paraspinal muscles in addition to the well-described involvement of the shoulder- and hip-girdle. Stabilization and mobility of the spine is dependent on the paraspinal muscles. Affection of these muscles might compromise balance, posture and the ability to walk, which should be taken into account in the clinical evaluation and management of LGMD2I patients.