Contributing factors to muscle weakness in children with cerebral palsy

Abstract

The aim of this study was to determine the extent of ankle muscle weakness in children with cerebral palsy (CP) and to identify potential causes. Maximal voluntary contractions of plantar (PF) and dorsiflexors (DF) were determined at optimal angles in knee flexion and extension in both legs of 14 children with hemiplegia (7 males, 7 females) and 14 with diplegia (8 males, 6 females). Their results were compared to 14 age- and weight-matched control participants (5 males, 9 females). Muscle cross-sectional areas of soleus, posterior, and anterior compartment muscles were determined from MRIs in 14 children with CP (eight diplegia, six hemiplegia) and 18 control children. Specific tension (torque/unit area) of PF and DF was determined from torque and cross-sectional area results. Muscle volumes of PF and DF were also determined in both legs of five control children and five with hemiplegia. Muscle EMG was recorded from soleus, medial gastrocnemius, and tibialis anterior during each maximal voluntary contraction. Mean amplitude was significantly reduced in PF and DF in both CP groups and significantly higher levels of coactivation of antagonists were found compared to control participants. Strength of PF and DF was significantly reduced in both CP groups, but more importantly the muscles were found to be weak based on significantly reduced specific tensions. The PF were most affected, particularly in the group with hemiplegia. It is believed that an inability to maximally activate their muscles contributed to this weakness. A combination of incomplete activation and high levels of PF coactivation are thought to have contributed to DF weakness.

Are Muscle Volume Differences Related to Concentric Muscle Work During Walking in Spastic Hemiplegic Cerebral Palsy?

“…Our results are consistent with those of previous studies reporting muscles are smaller on the hemiplegic side and the differences are more pronounced distally in the limb [5,10]. We cannot conclude whether the differences in muscle volume arise because brain injury alters patterns of innervation and growth factor release or because of disuse, with less work performed over the joints and growth plates in the hemiplegic limb.…”

“…Several studies show muscle volume correlates with strength, and training is beneficial in CP [1,6]; however, age, severity of involvement, and degree of improvement in strength and gait vary greatly in these studies [1,2,6,18]. Elder et al [5] reported an inability to perform voluntary maximal contractions contributed to muscle weakness in patients with CP.…”

“…In addition, during gait, a bilateral shift of concentric muscle work from ankle plantar flexors to hip extensor muscles reportedly occurs in children with hemiplegic CP [24]. Although there are reports on muscle volume and muscle work, it is still unclear whether and how muscle volume influences gait [5,10,12,24].…”

The effects of botulinum toxin injection frequency on calf muscle growth in young children with spastic cerebral palsy: A 12-month prospective study

“…A recent systematic review [20] concluded, on the basis of cross-sectional studies, that there was consistent evidence for reduced calf muscle size in the paretic limb in spastic CP compared to typically developing (TD) peers [21][22][23][24][25]. Barber et al [26] subsequently showed that medial gastrocnemius (MG) muscle physiological crosssectional area (PCSA), but not fascicle length, was reduced by 27 % in children aged 2-5 years with spastic CP who had not commenced BoNT-A treatment compared to TD peers.…”

Muscle-specific changes in length-force characteristics of the calf muscles in the spastic Han-Wistar rat

“…muscle spasticity; mechanical properties; myofascial force transmission; muscle stiffness MUSCLE SPASTICITY HAS BEEN defined as a "velocity-depended resistance to stretch" (24) and arises secondary to upper motoneuron lesions with cerebral palsy and stroke as the most common examples (12). Individuals suffering from spasticity typically experience muscle weakness, enhanced joint stiffness, increased muscle tone, reduced range of joint motion, increased antagonistic co-contraction, and exaggerated reflexes (1,3,6,12,13,32,41,48). These effects severely impair the ability to perform daily activities, and treatment is often needed.…”