Alterations of treatment-naïve pelvis and thigh muscle morphology in children with cerebral palsy

Abstract

Lower limb (LL) muscle morphology and growth are altered in children with cerebral palsy (CP). Muscle alterations differ with age and with severity of motor impairment, classified according to the gross motor classification system (GMFCS). Muscle alterations differ also with orthopedic intervention, frequently performed at the level of the shank muscles since an early age, such as the gastrocnemius. The aim was to investigate the alterations of treatment-naïve pelvis and thigh muscle lengths and volumes in children with GMFCS levels I and II, of varying ages.

17 children with CP (GMFCS I: N = 9, II: N = 8, age: 11.7 ± 4 years), age-matched to 17 typically developing (TD) children, underwent MRI of the LL. Three-dimensional reconstructions of the muscles were performed bilaterally. Muscle volumes and lengths were calculated in 3D and compared between groups. Linear regression between muscle volumes and age were computed.

Adductor-brevis and gracilis lengths, as well as rectus-femoris volume, were decreased in GMFCS I compared to TD (p < 0.05). Almost all the reconstructed muscle volumes and lengths were found to be altered in GMFCS II compared to TD and GMFCS I. All muscle volumes showed significant increase with age in TD and GMFCS I (R² range: 0.3–0.9, p < 0.05). Rectus-femoris, hamstrings and adductor-longus showed reduced increase in the muscle volume with age in GMFCS II when compared to TD and GMFCS I.

Alterations of treatment-naïve pelvis and thigh muscle volumes and lengths, as well as muscle growth, seem to increase with the severity of motor impairment in ambulant children with CP.

Introduction

Cerebral palsy is a common neurological disorder with a prevalence ranging between 1.5 and 2.5 per 1000 births according to the Surveillance of Cerebral Palsy In Europe (SCPE, 2002). Spasticity, contractures (Farmer and James, 2001), lack of muscle selectivity (Fowler et al., 2010), muscle weakness (Elder et al., 2003) and motor disability are usually encountered in these patients (Bax et al., 2005). A large proportion of children with CP are ambulant (SCPE, 2002) and present alterations in their walking abilities that can be classified according to gross motor classification system (GMFCS) levels (Palisano et al., 2008). Walking abilities in children with CP are highly related to the reduction in lower limb (LL) muscle force (Ross and Engsberg, 2007), which is known to be correlated to lower limb muscle morphology (Moreau et al., 2012, Moreau et al., 2010). Muscle morphology has been previously shown to be progressively affected during growth in these patients (Barber et al., 2016), in part due to the reduction in physical activity and motion abnormalities (Karagounis and Hawley, 2010).

Only a few studies, which included only children with histories of various medical and surgical interventions, have investigated muscle lengths (Fry et al., 2003, Handsfield et al., 2016, Oberhofer et al., 2010), volumes (Handsfield et al., 2016, Noble et al., 2014, Oberhofer et al., 2010), or cross-sectional areas (Handsfield et al., 2016) of the LL in children with CP, with conflicting results. Moreover, these parameters have never been studied in children with different GMFCS levels. Furthermore, muscle lengths and volumes are known to be affected by orthopedic interventions, which are often performed from a very young age (casting, botulinum toxin, soft tissue surgery) (Handsfield et al., 2016). There are currently no studies evaluating the natural evolution of the muscular pathology in children with CP by eliminating the bias of surgical and medical interventions on pelvis and thigh muscles. Furthermore, while it is known that volume alterations in these children become more significant with age, this was only reported for the gastrocnemius medius (Barber et al., 2016, Barber et al., 2011), and possible alterations for the remaining pelvis and thigh muscles have not yet been investigated.

The aim of this study was to investigate the volume and length alterations of treatment-naïve pelvis and thigh muscles in ambulant children with GMFCS levels I and II, of varying ages.