title: Heterogeneity of muscle fat infiltration in children with spina bifida.
abstract: Children with spina bifida have well recognized functional deficits of muscle, but little is known about the associated changes in muscle anatomy and composition. This study used water-fat magnetic resonance imaging (MRI) to measure fat infiltration in the lower extremity muscles of 11 children with myelomeningocele, the most severe form of spina bifida. MRI measurements of muscle fat fraction (FF) were compared against manual muscle test (MMT) scores for muscle strength. The FF measurements were objective and reliable with mean inter-rater differences of <2% and intraclass correlation coefficients>0.98. There was a significant inverse relationship between muscle FF and MMT scores (P ≤ 0.001). Surprisingly, however, muscles with negligible strength (MMT 0-1) exhibited a bimodal distribution of FF with one group having FF>70% and another group having FF<20%. The MRI also revealed striking heterogeneity amongst individual muscles in the same muscle group (e.g., 4% fat in one participant's lateral gastrocnemius vs. 88% in her medial gastrocnemius), as well as significant asymmetry in FF in one participant with asymmetric strength and sensation. These results suggest that quantitative water-fat MRI may serve as a biomarker for muscle degeneration which may reveal subclinical changes useful for predicting functional potential and prognosis.
authors.affiliation: Children's Orthopaedic Center and Department of Radiology, Children's Hospital Los Angeles, United States. Electronic address: twren@chla.usc.edu.
authors.forename: Tishya A L
authors.initials: TA
authors.lastname: Wren
authors.forename: Skorn
authors.initials: S
authors.lastname: Ponrartana
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Speybroeck
authors.forename: Deirdre D
authors.initials: DD
authors.lastname: Ryan
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Chia
authors.forename: Houchun H
authors.initials: HH
authors.lastname: Hu
mesh_terms: D000273:Adipose Tissue / Q000473:pathology* / Q000502:physiology; D000293:Adolescent; D001834:Body Water / Q000502:physiology; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D008591:Meningomyelocele / Q000473:pathology* / Q000503:physiopathology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000473:pathology* / Q000502:physiology; D011379:Prognosis; D015203:Reproducibility of Results; D016135:Spinal Dysraphism / Q000473:pathology* / Q000503:physiopathology
keywords: Muscle fat fraction; Myelomeningocele; Spina bifida; Water-fat MRI