Causal Relation Between Spasticity, Strength, Gross Motor Function, and Functional Outcome in Children With Cerebral Palsy: a Path Analysis

It is well-known that children with cerebral palsy can display impairments in gross motor function, muscle strength, and spasticity (involuntary muscle contractions). What is not as well-known is the causal relationship between these motor function impairments and the child's functional outcome, or the child's social and vocational abilities. A study by Dr. Eun Young Park of Jeonju University looked into this causal relation and tested models of functional outcomes to propose a path analysis.

Objective of the Analysis and Definitions

The goal of the Jeonju University study was to establish a causal relation between motor impairment and functional outcome in children with cerebral palsy. It did so by studying three common problems in children with this condition: spasticity, strength, and gross motor function. Spasticity is a motor disorder that causes muscle tightness or stiffness, due to continuous contractions.

Typically, damage to the part of the brain that controls voluntary movement causes spasticity. In children with cerebral palsy, spasticity can have a negative effect on movement, gait, and speech. Cerebral palsy can also affect muscle strength, often in the shoulders, arms, and hands. Muscle weakness is a common challenge children with cerebral palsy face, and one that often coincides with spasticity. Many children engage in strength and resistance training interventions to improve muscle weakness, starting early in life.

Gross motor function refers to all physical skills involved in body movement, including core muscles and everyday functions. How a child sits, stands, walks, runs, and jumps all come down to his or her gross motor function. Children with cerebral palsy often have impaired motor function, ranging from poor balance and coordination to only being able to keep one's head up and control arm and leg movements. A child's score on the Gross Motor Function Classification System (GMFCS) describes capability level.

Functional outcome refers to an individual's recovery in terms of social and vocational ability. It is in contrast to clinical outcome, which focuses on recovery in terms of symptom resolution. The functional outcome measures in children with cerebral palsy include speech, language, and cognitive development, as well as gross motor skills (body structure and function), activity, and participation. The objective of the Jeonju University study was to confirm the causal relationship between three common symptoms of cerebral palsy and functional outcome, to yield a better understanding of what types of therapies could improve the latter.

What did the Study Find?

Researchers in the study point out that no one has conclusively established the relation between motor ability and spasticity. Existing evidence of a causal relation between motor impairment and functional outcome in children with cerebral palsy come from causal relation analysis. Researchers also note that it is a common opinion that weakness is not a major problem in children with cerebral palsy. This means many physicians do not recommend muscle strengthening for children with cerebral palsy, due to the belief that it would increase spasticity.

The study involved 81 child participants, all diagnosed with cerebral palsy. The participants either attended a school for children with disabilities or received rehabilitation therapy in Korea. Most participants (49.4%) were in level V of the GMFCS, or the most severe level of impairment. Researchers used a range of tests to measure spasticity, strength, and gross motor function in test subjects. Then, researchers measured each child's function outcome using the Pediatric Evaluation of Disability Inventory (PEDI) Functional Skills scales, which include:

  1. Functional skills
  2. Caregiver assistance
  3. Modifications

Researchers used a path analysis to investigate the causal relations between all measures recorded. The results of the path analysis found that spasticity, strength, and gross motor function variables do in fact influence functional outcome. It also confirmed that functional outcome mediated gross motor function in children with spasticity. The results of the study suggest that the modern understanding of health and disability should take into greater account the social aspects of disability.

What Does the Study Mean for Parents?

The study concluded that activity-based intervention was more effective at reducing functional limitations in children with cerebral palsy than impairment-based intervention. Based on these findings, the study presented a base model from which future researchers can develop causal models between gross motor function impairments and functional outcomes.

The study provided the first published path analysis of functional outcome in children with cerebral palsy, as well as confirmed that the causal factors of spasticity and muscle weakness relate to gross motor function. Finally, it revealed gross motor function to be a causal factor in functional outcome. For parents of children with cerebral palsy, this study points to the need for greater emphasis on activity-based intervention, rather than impairment-based intervention only.

Phrased another way, children with cerebral palsy may see greater improvement in occupational and vocational outcomes with therapies that focus on activity and motor function, rather than that focus only on medical symptoms. Based on the findings of the study, physical therapy intervention that focuses on motor impairment can in fact improve a child with cerebral palsy's functional outcome.