The relationship between lower limb muscle volume and body mass in ambulant individuals with bilateral cerebral palsy

Jonathan J Noble,Martin Gough,Adam P Shortland,Andrew P Lewis,Emily Chruscikowski,Nicola R D Fry

doi:10.1186/s12883-017-1005-0

Abstract

BackgroundIndividuals with cerebral palsy have smaller muscle volumes normalised to body mass than their typically developing peers. The aim of this study is to investigate the relationship between lower limb muscle volume and body mass in young people with bilateral cerebral palsy and their typically developing peers.MethodsTwenty-five participants with bilateral cerebral palsy (aged 14.7±3.0 years, GMFCS level I-III) and 25 of their typically developing peers (aged 16.8±3.3 years) took part in this study. None of the participants had undergone orthopaedic surgery, botulinum toxin injections, or serial casting in the previous year. All participants underwent magnetic resonance imaging of both lower limbs. Nine major muscles of each lower limb were individually manually segmented and the muscle volumes calculated.ResultsBody mass and total lower limb muscle volume were significantly linearly related in both the cerebral palsy (R2 = 0.75, p<0.001) and typically developing (R2 = 0.77, p<0.001) groups. The slope of the relationship between muscle volume and body mass was significantly shallower in the cerebral palsy group compared to the typically developing group (p=0.007).ConclusionsThis cross-sectional study suggests that the increase in size of lower limb muscles relative to body mass is reduced in adolescents and young adults with cerebral palsy. Longitudinal studies are required to further investigate altered muscle growth trajectories in this group and their impact on long-term mobility.

Highlights

Individuals with cerebral palsy have smaller muscle volumes normalised to body mass than their typically developing peers
Muscles in the lower limbs of children with Cerebral palsy (CP) are reduced in size relative to their body mass compared to their typically developing (TD) peers [12,13,14,15,16,17], with greater muscle volume deficit increasing with increasing motor impairment measured using the gross motor function classification system (GMFCS) [12]
The subjects with CP were not subcategorised into bilateral and hemiplegic subjects with the infants with CP having their more affected leg assessed [18]. This cross-sectional study suggested that medial gastrocnemius growth was reduced for infants with CP compared to their TD peers with respect to age, body mass, height, and tibial length [18]

Summary

Introduction

Individuals with cerebral palsy have smaller muscle volumes normalised to body mass than their typically developing peers. The subjects with CP were not subcategorised into bilateral and hemiplegic subjects with the infants with CP having their more affected leg assessed [18] This cross-sectional study suggested that medial gastrocnemius growth was reduced for infants with CP compared to their TD peers with respect to age, body mass, height, and tibial length [18]. Barber et al recently reported a large cross sectional study of medial gastrocnemius muscle volume normalised to body mass with age in ambulant children with unilateral and bilateral CP and their TD peers aged 2 to 9 years [19]. Direct comparison of the data from these works is difficult because Herskind et al use non-normalised volume data but Barber et al reported a muscle volume to body mass ratio

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