Connective Tissue Infiltration and Subcutaneous Fat in Fascioscapulohumeral Muscular

CONNECTIVE TISSUE INFILTRATION AND SUBCUTANEOUS FAT IN FASCIOSCAPULOHUMERAL MUSCULAR DYSTROPHY-AFFECTED BICEPS BRACHII MUSCLE.

Guy Sovak, BSc, MSc, PhD., John J. Triano DC, PhD. Dave Soave, MSc.,Steve Tran MSc, Lindsay Johnston and Marliegh Edwards.

Canadian Memorial Chiropractic College, Toronto, Canada. Graduate education and research. Phone: 416 482 2340 email:

BACKGROUND Facioscapulohumeral muscular dystrophy (FSHD) is the third most common of the inherited muscular dystrophies [1]. Quantitative ultrasound has been used to evaluate the severity of pathology and the relationship of pathology with strength and function[2]. This feasibility study examined quantitatively the content of epimuscular fat and intramuscular connective tissue vs clinical severity scale (CSS) [3] as a baseline for elastographic estimates of tissue strata strain, in progress. Quantifying the differences between distributions of epimuscular fat and intramuscular connective tissue inFSHD and healthy controls may allow for a better understanding of how muscle distributes load during motion.

METHODSA total of 17 subjects, including FSHD (n=8) and controls (n=9), were analyzed. The biceps brachii muscles of all subjects were evaluated using ultrasound technology (Ultrasonix, Burnaby, BC). Clinical severity was estimatedby CCS. Echogenicity of connective tissue/fat and subcutaneous fat werecalculated using MaTLlab software specifically programmed to quantify the muscle content of connective tissue and fat.

RESULTS Patients with FSHD consistently demonstrated an increase in connective tissue/fat infiltration and subcutaneous fat when compared to the healthy controls. There were no significant correlations found between CSS measurements and the amount of subcutaneous fat. A significant positive correlation was found between clinical severity and connective tissue/fat muscle infiltration (r=0.82) while a significant negative (r=-0.76) correlation was found between biceps muscle circumference and connective tissue/fat infiltration, and between muscle strength and connective tissue/fat infiltration (r=-0.91).

CONCLUSION Patients with FSHD have an increased amount of connective tissue/fat infiltration in their biceps brachiiand an increase in overlying subcutaneous fat compared to controls. The more severe the FSHD is the greater amount of connective tissue/fat infiltration. Subcutaneous fat was not related to clinical severity.

REFERENCE

[1] Olsen D, Gideon P, Dysgaard Jeppesen T & Vissing J. Leg muscle involvement in fascioscapulohumeral muscular dystrophy assessed by MRI. J Neurol. 253:1437-1441, 2006

[2] Zaidman CM, Connolly AM, Malkus EC, Florence JM, Pestronk A.Quantitative ultrasound using backscatter analysis in Duchenne and Becker muscular dystrophy.

NeuromusculDisord. 2010 Dec;20(12):805-9.

[3] 1. Ricci E, Galluzzi G, Deidda G, Cacurri S, Colantoni L, Merico B, Piazzo N, ServideiS,Vigneti E, Pasceri V, et al. Progress in the molecular diagnosis of facioscapulohumeral muscular dystrophy and correlation between the number of KpnI repeats at the 4q35 locus and clinical phenotype. Ann Neurol 1999; 45(6): 751-757.