It is commonly assumed that exaggerated stretch reflex activity and the resulting increased muscle tone in ankle plantar flexors contribute to reduced ankle joint movement during gait in children with cerebral palsy (CP). We investigated the contribution of sensory feedback mechanisms to ankle plantar flexor muscle activity during treadmill walking in 20 children with CP and 41 control children. Stretch responses in plantar flexor muscles evoked in stance by dorsiflexion perturbations showed an age-related decline in control children but not in children with CP. In swing responses were abolished in control children, but not in children with CP. Removal of sensory feedback to the soleus muscle in stance by shortening the plantar flexors produced a drop in soleus EMG activity of a similar size and latency in control children and children with CP. Soleus EMG activity was observed in swing in a similar proportion in both groups. Shortening of the plantar flexors in swing caused a larger drop in Soleus EMG in control children than in children with CP. The lack of age related decline in stretch reflexes in the stance phase and the inability to suppress the reflex in the swing phase is likely related to lack of maturation of corticospinal control in children with CP. However, since they did not show soleus EMG activity to a larger extent than control children in swing and since sensory afferent feedback did not contribute more to their muscle activity, spasticity is unlikely to contribute to foot drop and toe walking.
"Foot drop and toe walking are among the most frequent clinical problems in children with cerebral palsy (Fowler et al., 2010). The main underlying cause of these problems is reduced force in the ankle dorsiflexor muscles secondary to a lesion of the motor cortex or the corticospinal tract (Bland et al., 2011; Moreau et al., 2012; Petersen et al., 2013; Willerslev-Olsen et al., 2014a). In healthy children, improved control of the ankle dorsiflexors in the swing phase of walking parallels maturation of the corticospinal tract across the age range 4–15 years (Hodapp et al., 2007a; Petersen et al., 2010, 2013). "
"Pronounced weakness in ankle dorsiflexors is thus commonly seen in children with CP (Bland et al., 2011; Moreau et al., 2012; Petersen et al., 2013) and this has been shown to be related to impaired corticospinal drive to the muscles during gait (Petersen et al., 2013). In addition, increased stiffness of the passive elastic elements in the ankle muscles has been shown to develop at an early age and cause severe functional gait problems in children with CP (Dietz et al., 1981; Willerslev-Olsen et al., 2013a, 2013b). Without treatment these muscular alterations become permanent in the form of contractures which greatly reduces the range of movement in the joint and at some point usually necessitates surgical intervention (Hagglund & Wagner, 2011). "
[Show abstract][Hide abstract] ABSTRACT: Background:
Foot drop and toe walking are frequent concerns in children with cerebral palsy (CP). Increased stiffness of the ankle joint muscles may contribute to these problems.
Does four weeks of daily home based treadmill training with incline reduce ankle joint stiffness and facilitate heel strike in children with CP?
Seventeen children with CP (4-14 years) were recruited. Muscle stiffness and gait ability were measured twice before and twice after training with an interval of one month. Passive and reflex-mediated stiffness were measured by a dynamometer which applied stretches below and above reflex threshold. Gait kinematics were recorded by 3-D video-analysis during treadmill walking. Foot pressure was measured by force-sensitive foot soles during treadmill and over-ground walking.
Children with increased passive stiffness showed a significant reduction in stiffness following training (P = 0.01). Toe lift in the swing phase (P = 0.014) and heel impact (P = 0.003) increased significantly following the training during both treadmill and over-ground walking.
Daily intensive gait training may influence the elastic properties of ankle joint muscles and facilitate toe lift and heel strike in children with CP. Intensive gait training may be beneficial in preventing contractures and maintain gait ability in children with CP.
[Show abstract][Hide abstract] ABSTRACT: Clinical assessment of spasticity is compromised by the difficulty to distinguish neural from non-neural components of increased joint torque. Quantifying the contributions of each of these components is crucial to optimize the selection of anti-spasticity treatments such as Botulinum Toxin (BTX). The aim of this study was to compare different biomechanical parameters that quantify the neural contribution to ankle joint torque measured during manually-applied passive stretches to thegastrocsoleus in children with spastic cerebral palsy (CP). The gastrocsoleus of 53 children with CP (10.9 ± 3.7yrs; females n=14; bilateral/unilateral involvement n=28/25; Gross Motor Functional Classification Score I-IV) and 10 age-matched typically developing (TD) children were assessed using a manually-applied, instrumented spasticity assessment. Joint angle characteristics, root mean square electromyography and joint torque were simultaneously recorded during passive stretches atincreasing velocities. From the CP cohort, 10 muscles were re-assessed for intra-rater reliability and 19 muscles were re-assessed 6 weeks post-BTX. A parameter related to mechanical work, containing both neural and non-neural components, was compared to newly developed parameters that were based on the modeling of passive stiffness and viscosity. The difference between modeled and measured response provided a quantification of the neural component. Both types of parameters were reliable (ICC>0.95) and distinguished TD from spastic muscles (p<0.001). However, only the newly developed parameters significantly decreased post-BTX (p=0.012). Identifying the neural and non-neural contributions to increased joint torque allows for the development of individually tailored tone management.
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