Cerebral Palsy Outcome Measures

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Original Editor - Kim Jackson as part ICRC Cerebral Palsy Content Development Project.

Top Contributors - Naomi O'Reilly, Kim Jackson, WikiSysop, Rucha Gadgil, 127.0.0.1, Jess Bell and Olajumoke Ogunleye  

Introduction

Cerebral palsy (CP) is a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to non-progressive disturbances that occurred in the developing foetal or infant brain (Rosenbaum et al., 2007). Rehabilitation in cerebral palsy focuses on promoting mobility, functional independence, and quality of life through various therapeutic strategies. In order to be able to provide quantifiable data on functional changes over time, it is important to use outcome measures, to track progress, modify interventions, and demonstrate the impact of therapy to patients, families, and healthcare systems.

Outcome Measures

An Outcome Measure is the result of a test that is used to objectively determine the baseline function of a patient at the beginning of treatment. Once treatment has commenced, the same instrument can be used to determine progress and treatment efficacy. With the move towards Evidence Based Practice (EBP) in the health sciences, objective measures of outcome are important to provide credible and reliable justification for treatment. The instrument should also be convenient to apply for the therapist and comfortable for the patient. An integral part of evaluating clinical practice is to objectively assess the intervention and measure it against a set of outcomes to determine its efficacy. Prior to determining any orthotic intervention, the careful choice of treatment goals and aims is essential in children with complex neuromuscular disability in order to identify and determine appropriate outcome measures. 

Outcome measures can assess various dimensions, including motor skills, functional independence, quality of life, participation in daily activities, and specific impairments like spasticity or dysarthria. Outcome measures:

• Enhance Treatment Planning and Decision-Making: Outcome measures contribute to individualized treatment planning by providing valuable insights into a patient's functional abilities and limitations. The Gross Motor Function Classification System (GMFCS) is widely utilised in CP rehabilitation and helps clinicians establish baseline assessments, set realistic goals, and monitor progress over time (Palisano et al., 2008). Such data-driven approaches empower clinicians to make informed treatment decisions and optimise outcomes.

• Facilitate Interprofessional Collaboration: CP rehabilitation often involves a multidisciplinary team. Standardised outcome measures act as a common language, facilitating communication and collaboration among healthcare professionals. For instance, the Manual Ability Classification System (MACS) evaluates upper limb function and assists clinicians from various disciplines in sharing and interpreting assessment results (Eliasson et al., 2006). This collaborative approach supports a comprehensive and coordinated care plan.

• Monitor Progress and Evaluate Treatment Efficacy: Regular assessment of functional abilities is crucial for monitoring progress and evaluating the effectiveness of interventions. The Paediatric Evaluation of Disability Inventory (PEDI) assesses functional capabilities in self-care, mobility, and social function domains (Haley et al., 1992). By utilising such measures, clinicians can track changes in performance, identify the impact of interventions, and optimise outcomes for individuals with CP.

Clinician Reported Outcome Measures

Clinician Reported Outcome Measures (CROMs) used in the literature to evaluate the efficacy of orthoses and specifically AFOs for children with Cerebral Palsy include the Timed Up and Go test (TUG), the 88 and 66 item Gross Motor Function Measure (GMFM-88 and GMFM-66 respectively), Gross Motor Performance Measure (GMPM), Clinical Gait Assessment Score (CGAS), Pediatric Balance Scale (PBS) and the Standardised Walking Obstacle Course (SWOC). All of these outcome measures have been proven to be valid and reliable to evaluate motor function and performance in children with Cerebral Palsy.      

Patient Reported Outcome Measures

A Patient Reported Outcome Measure (PROM) such as the Paediatric Outcomes Data Collection Instrument (PODCI), the Pediatric Evaluation of Disability Inventory (PEDI) or Gillette Functional Assessment Questionnaire (FAQ), permits the child and family to provide information from their own everyday environment that relates not only to the function of the child’s gait but also to quality of life issues. It is not always possible for healthcare professionals to observe children in their own environment, which makes the PROM a powerful and valuable evaluation tool.

The PODCI is a parent-reported outcome measure that assesses the mobility, physical function, comfort, happiness and expectations of the healthcare interventions in children with musculoskeletal health issues.  In accordance with the ICF values, it not only focuses on assessing function and performance following healthcare interventions, but also evaluates quality of life issues. The PODCI has good reliability and validity when evaluating quality of life issues and walking function in children with Cerebral PalsyP, but does have floor and ceiling effects in the transfer and mobility scales.   It demonstrates only a modest sensitivity to detect changes of walking function in children with CP following orthopaedic surgery as the scoring system is considered too expansive to detect subtle changes.   Lee et al.  found statistically significant improvements in PODCI scores following orthopaedic surgery, but only minimal clinically relevant results. This may mean the PODCI may not be sensitive enough to evaluate the effects of orthotic intervention on mobility and provide results that are clinically relevant.

The International Classficiation of Function, Disability and Health

The International Classification of Function, Disability and Health (ICF) is the World Health Organization's framework for measuring health and disability at both individual and population levels. The ICF has shifted the focus of the impairments in children with Cerebral Palsy from restriction in joint ROM or abnormal muscle tone to the evaluation of functions by assessing the quantitative and qualitative aspects of a child’s Activities of Daily Living (ADL). It states that the focus of rehabilitation should be shifted from identifying a person’s disability to focusing on enhancing a person’s function, ability and performance quality for each individual in a contextual manner. The ICF identified domains that should be evaluated in children with Cerebral Palsy to include body function and structure, activity and participation. A consensus-based survey of clinicians, parents and youth with Cerebral Palsy supported these domains as relevant to the evaluation of all health care interventions in children with Cerebral Palsy.

The primary goal of orthotic treatment of ambulant children with Cerebral Palsy (GMFCS I-III) is to optimise their gait. This is with the expectation that it will preserve or improve their physical function and provide them with the ability to increase their participation in physical activities, recreation and sport.  Evaluating orthotic intervention requires the use of outcome measures that will not only assess the function and quality of walking, but also the health related quality of life. Quality of life is frequently used as a ‘catch all’ expression for any self-reported measure, even when the instrument is capturing information objectively verifiable as functional ability, activities or participation.

Given the heterogeneous nature of the Cerebral Palsy population, the goals of rehabilitation are often widely distributed across the ICF domains. This may result in problems interpreting the outcome when using standardised outcome measures alone.   Items in a standardised outcome measure may not match the individual treatment goals and even if they do, the outcome may not necessarily represent goal attainment.

Outcome Measures for Children with Cerebral Palsy

When choosing outcome measures it is important to focus on the expectations for children with CP of the same age and gross motor function, rather than those for children without developmental delays.

Gross Motor Function Measure

Gross Motor Function Measure (GMFM): This tool is specifically designed for children with cerebral palsy and focuses on gross motor function. The GMFM consists of 88 items grouped into five dimensions: lying & rolling, sitting, crawling & kneeling, standing, and walking, running & jumping.

Gross Motor Function Measure (GMFM): This tool includes an algorithmic approach to identify item sets of the 66-item version of the GMFM (GMFM-66) to be administered to individual children. The GMFM-66-IS scores were validated using data from several studies and found to have excellent agreement with the full GMFM-66 both at a single assessment and across repeat assessments​1​.

The Gross Motor Functional Measure (GMFM) is a criterion-referenced measure expressly constructed for the purpose of assessing capacity to perform specific functions and evaluate change in the gross motor function of children with CP.  The GMFM-88 and 66 item tools were especially developed to assess the gross motor function in children with CP and are among the few outcome measures that have displayed sensitivity to change when evaluating orthotic intervention. There have also been strong correlations established between a child’s GMFCS level and the scores attained in the GMFM sections D and E.  A large study with 257 participants conducted by Russell et al. , described the ‘D’ dimension of standing and ‘E’ dimension of walking, running and jumping of the GMFM to be sensitive to functional change in children with CP when using AFOs.

The 88 and 66 item GMFM cover the five dimensions of lying and rolling, sitting, crawling and kneeling, standing, and walking running and jumping. Administering the full five dimensions of the GMFM 88 or 66 item scales is a time consuming process, often taking in excess of 45 minutes, which means clinical utility is often low. The particular dimensions ‘D’ and ‘E’ of the GMFM may be assessed separately when evaluating a specific area of function in order to save time, while still retaining reliability, validity and sensitivity of the full measure. However, after 5 years of age, changes in a child’s motor abilities are more related to developing and refining motor functions in specific environments, rather than the development of basic gross motor skills.  Ceiling effects have been identified in older or more able children assessed with the GMFM.  This may explain why some studies described larger improvements in gross motor function in children younger than 5 years of age when compared with older children.

Paediatric Evaluation of Disability Inventory

Paediatric Evaluation of Disability Inventory (PEDI): The PEDI is a comprehensive tool for evaluating function in children with disabilities. It measures capability and performance in three domains: self-care, mobility, and social function.

Peadiatric Evaluation of Disability Inventory (PEDI): A revised version of the PEDI, known as the PEDI computer-adaptive tests (PEDI-CAT), was developed with four content domains: daily activities, mobility, social/cognitive, and responsibility. The PEDI-CAT has demonstrated excellent accuracy compared with the administration of all items, suggesting it can be an accurate and precise assessment of children's daily performance at all functional levels​2​

The PEDI is a parent reported outcome measure administered by a clinician that has shown to be reliable, repeatable and valid in children and adolescents with CP from ages 2-18 to evaluate motor function, self-care and participation.   Its clinical relevance is further supported by evidence that motor skills are not necessarily representative of overall functional improvements following healthcare interventions as it assesses not only capability but also quality of performance.  The mobility scales in the PEDI have less detail than the GMFM scales. As a result, the PEDI demonstrates only moderate responsiveness to change in motor skills and should not be used in isolation to evaluate the ICF domain of body function and structure.  However, unlike the GMFM, it does have the advantage of being able to assess a child’s gross motor function in their everyday environment and is therefore more reflective of community function. Despite the PEDI being a patient-reported outcome measure, it still requires a trained healthcare professional to administer the evaluation. The PEDI covers the broad range of motor function, self-care and participation and is very thorough. It can take more than 30 minutes to complete, which may take up already valuable clinical time.

Gillette Functional Ability Questionnaire (FAQ)

The Gillette Functional Ability Questionnaire (FAQ) is a reliable, repeatable and valid condition-specific functional scale that was developed especially for children with Cerebral Palsy.  (TABLE 4) Similar to the PEDI, it assesses a child’s walking ability across different domains. However it only focuses on the ability to achieve a particular level and not the capability. No training or equipment is necessary to administer the 10-level, parent-reported questionnaire and it is quick and easy to apply. It has shown sensitivity to change in children with Cerebral Palsy who have undergone orthopaedic surgery, but it is unclear as to whether it would be sensitive and responsive to change following orthotic intervention.  

Goal Attainment Scaling (GAS)

Goal Attainment Scaling (GAS): GAS is a method of scoring the extent to which patients' individual goals are achieved in the course of intervention. In cerebral palsy, it can be used to assess the effectiveness of interventions like botulinum toxin A injections, selective dorsal rhizotomy, and intrathecal baclofen therapy. The use of GAS measures allows the orthotist to not only perform the clinical evaluation of the orthotic intervention, but also ensure that patient and family satisfaction is measured. The clinician, parents and child are able to identify specific areas for evaluation, quickly perform the assessment and provide a score from a predetermined ordinal scale. In heterogeneous populations, GAS measures have exhibited increased responsiveness to the ICF domain of activity and participation than those of traditional standardised outcome measures.   

Cerebral Palsy Quality of Life Questionnaire (CP QOL)

Cerebral Palsy Quality of Life Questionnaire (CP QOL): This is a condition-specific quality of life measure for children with cerebral palsy. It includes child self-report and primary caregiver proxy report forms.

Child Health Assessment Questionnaire (CHAQ)

Child Health Assessment Questionnaire (CHAQ): In a large cohort of patients with juvenile idiopathic inflammatory myopathy (IIM), the CHAQ exhibited internal reliability, construct validity, and strong responsiveness, making it a valid measure of physical function in juvenile IIM. It is appropriate for use in therapeutic trials and potentially in the clinical care of these patients​3​.

Peabody Developmental Motor Scales-2 (PDMS-2)

Peabody Developmental Motor Scales-2 (PDMS-2): Unfortunately, I had difficulties accessing and quoting information about the PDMS-2 due to technical issues with the available sources. I was able to identify relevant studies, but couldn't quote from them directly. Broadly, the studies I found suggest that the PDMS-2 has demonstrated validity and reliability in assessing motor skills in children. I would recommend looking into these studies further for more detailed information.

PODCI

The PODCI is a parent-reported outcome measure that assesses the mobility, physical function, comfort, happiness and expectations of the healthcare interventions in children with musculoskeletal health issues.  In accordance with the ICF values, it not only focuses on assessing function and performance following healthcare interventions, but also evaluates quality of life issues. The PODCI has good reliability and validity when evaluating quality of life issues and walking function in children with Cerebral PalsyP, but does have floor and ceiling effects in the transfer and mobility scales.   It demonstrates only a modest sensitivity to detect changes of walking function in children with CP following orthopaedic surgery as the scoring system is considered too expansive to detect subtle changes.   Lee et al.  found statistically significant improvements in PODCI scores following orthopaedic surgery, but only minimal clinically relevant results. This may mean the PODCI may not be sensitive enough to evaluate the effects of orthotic intervention on mobility and provide results that are clinically relevant.

Timed Get Up (TUG)

The TUG is a basic test of functional mobility that evaluates an individual's ability to manoeuvre his or her body capably and independently to accomplish everyday tasks. The standard TUG test requires a child to rise from a seat with assistance of their arms and where the knees are flexed at 90°, stand momentarily, walk 3m, turn, return to the same seat, and sit down. Statistically significant differences in TUG scores have been observed in children across the GMFCS levels I-III, meaning it can act as a predictor of gross motor function.   The TUG has displayed excellent reliability, validity and repeatability in children aged 3-18 years who can understand instructions and do not have cognitive deficits.  It is an outcome measure that can quickly and easily evaluate the common orthotic treatment goal of improving the efficiency of gait and also has the potential to monitor change over time. It is also possible to employ the TUG in the child’s own environment, closely aligning with values of the ICF domains.

Importance of Evaluating Outcome Measures

Evaluating the reliability, validity, specificity, and responsiveness of outcome measures related to cerebral palsy (CP) is of paramount importance in ensuring accurate and meaningful assessment outcomes. These considerations are essential for determining the usefulness and applicability of outcome measures in CP rehabilitation.

• Reliability: Reliability ensures consistent results when an outcome measure is administered multiple times under similar conditions. High reliability minimises measurement error and accurately reflects an individual's true abilities.
• Validity: Validity ensures that an outcome measure accurately captures the targeted constructs or domains of interest. Establishing validity requires evidence-based validation studies that evaluate the measure's ability to assess what it intends to measure .
• Specificity: Specificity refers to an outcome measure's ability to detect changes in specific aspects of CP. Measures with high specificity focus on relevant domains or functions, allowing for the identification of even subtle improvements or deteriorations.
• Responsiveness: Responsiveness indicates an outcome measure's ability to detect meaningful changes over time. A responsive measure should be sensitive enough to detect even small changes in functional abilities, accurately reflecting progress or decline.

By thoroughly evaluating reliability, validity, specificity, and responsiveness in outcome measures, healthcare professionals can confidently select appropriate measures that capture the complexities of CP and reliably track progress.