Passive muscle properties are altered in children with cerebral palsy before the age of 3 years and are difficult to distinguish clinically from spasticity

Abstract

AIM Clinical determination of spasticity is confounded by the difficulty in distinguishing reflex from passive contributions to muscle stiffness. There is, therefore, a risk that children with cerebral palsy (CP) receive antispasticity treatment unnecessarily. To investigate this, we aimed to determine the contribution of reflex mechanisms to changes in the passive elastic properties of muscles and tendons in children with CP.METHOD Biomechanical and electrophysiological measures were used to determine the relative contribution of reflex and passive mechanisms to ankle muscle stiffness in 35 children with spastic CP (21 males, 14 females; mean age 9y, SD 3y 4mo; range 3-15y) and 28 control children without CP (19 males, nine females; mean age 8y 11mo, SD 2y 10mo; range 3-15y). Twenty-seven children were diagnosed as having spastic hemiplegia, six with spastic diplegia, and two with spastic tetraplegia. According to the Gross Motor Function Classification System, 31 children were classified in level I, two in level II, and two in level III.RESULTS Only seven children with spastic CP showed reflex stiffness outside the range of the control children. In contrast, 20 children with spastic CP showed abnormal passive muscle stiffness (p<0.001). No correlation between increased reflex or increased passive muscle stiffness and age was observed within the age range studied.

Sensory feedback to ankle plantar flexors is not exaggerated during gait in spastic hemiplegic children with cerebral palsy

“…Although all had been diagnosed as spastic prior to recruitment, four scored 0 on the Modified Ashworth Scale and in only five was a spastic catch noted. To objectively assess the passive and reflex-mediated stiffness components of the ankle plantar flexors, biomechanical and electrophysiological evaluation was performed according to Lorentzen et al (2010) and Willerslev-Olsen et al (2013). Briefly, children were seated in a reclining armchair with the examined foot attached to a footplate, which could be rotated by a motor (CEM model 26).…”

“…Perturbations were delivered every second in a random order until 10 trials per velocity were collected. Passive stiffness was calculated from the torque response at low velocities without stretch responses, whereas reflex stiffness was calculated from the torque response to the fastest perturbation (see Willerslev-Olsen et al 2013). The more spastic ankle joint was subsequently selected for further testing (7 children with CP were tested on the right and 13 on the left side; 9 children without CP were tested on the right and 32 on the left side).…”

“…Younger children with CP had reflexes and background EMG activity comparable to age-matched control children (P ϭ 0.25 and P ϭ 0.33, respectively). Although all children with CP had been found to be spastic by clinical examination, only three of them were found to have increased reflex stiffness at rest (Table 1; see Willerslev-Olsen et al 2013). These three children were not among the children who showed exaggerated reflexes during stance.…”

“…This was similarly observed by Hodapp et al (2007a) for the soleus H reflex. Hodapp et al (2007a) observed that the soleus H reflex when measured at rest was unrelated to age, and Willerslev-Olsen et al (2013) observed that reflex stiffness in children at rest was also unrelated to age. This suggests that the age-related decline of the stretch reflex observed in the present study is specific for gait and in all likelihood is related to maturation of the central control of gait.…”

Impaired gait function in adults with cerebral palsy is associated with reduced rapid force generation and increased passive stiffness

“…As pointed out in several recent studies, increased passive stiffness of the muscles, connective tissue, tendons and joints is difficult to distinguish clinically from spasticity and requires a combination of biomechanical and electrophysiological techniques in order to be correctly evaluated (Mirbagheri et al, 2004, Mirbagheri et al, 2005, Lorentzen et al, 2010, Willerslev-Olsen et al, 2013. It was suggested already by Volker Dietz and his co-workers more than 30 years ago that such changes in passive muscle stiffness may be the dominant cause of gait impairment in spastic subjects (Dietz et al, 1981, Berger et al, 1982, Dietz et al, 1983.…”