Neuromusculoskeletal Modeling of Muscle Spasticity

Cerebral palsy (CP) is a movement and posture disorder caused by an injury to the developing brain, with a prevalence in Sweden of about 2/1000 live births. Children with CP have walking difficulties, and decreased muscle mass and muscle function as compared to typically developing (TD) children. The extent of disability in CP depends on the severity and timing of the primary cerebral lesion and can be classified with the gross motor function classification system (GMFCS E\&R) that ranges from walking without limitations (I) to being transported in a wheelchair (V). Muscle function commonly deteriorates with age and contracture development is often clinically evident as early as at 4 years of age. In addition to being thinner and weaker, skeletal muscle in children with CP develop poor quality, i.e., increasingly higher amounts of fat and connective tissue at the expense of functional, contractile proteins. How long-term standard treatments for children with spastic CP including, training and orthotics use, with botulinum toxin (BoNT-A) treatment as an adjunct, affects muscle on functional, structural, and microscopic level in CP has not yet been published. Therefore, we will investigate the muscle function as well as functional mobility, structure, and spasticity. We will conduct functional mobility tests. Muscle strength will be measured with a rig-fixed dynamometer, and muscle structure will be measured with magnetic resonance imaging. The spasticity will be instrumentally assessed by the NeuroflexorTM, a machine measuring resistance in a muscle when a pedal is passively moving the participants foot at two different speeds. We will follow participants, for 1 year, with 4 measurements during this period. In order to better treat these children, we need to better understand the complex, interrelated interactions of musculoskeletal properties and function in children with CP. Our hypothesis is that muscle structure and function is affected by standard clinical tr