Age-related changes in energy efficiency of gait, activity, and participation in children with cerebral palsy
2010; Wiley; Volume: 53; Issue: 1 Linguagem: Inglês
10.1111/j.1469-8749.2010.03795.x
ISSN1469-8749
AutoresClaire Kerr, Brona McDowell, Jackie Parkes, Mike Stevenson, Aidan Cosgrove,
Tópico(s)Infant Development and Preterm Care
ResumoDevelopmental Medicine & Child NeurologyVolume 53, Issue 1 p. 61-67 Free Access Age-related changes in energy efficiency of gait, activity, and participation in children with cerebral palsy CLAIRE KERR, CLAIRE KERR School of Nursing and Midwifery, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorBRONA C MCDOWELL, BRONA C MCDOWELL Gait Analysis Service, Belfast Health and Social Care Trust, Musgrave Park Hospital, Stockman's Lane, Belfast, Northern Ireland.Search for more papers by this authorJACKIE PARKES, JACKIE PARKES School of Nursing and Midwifery, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorMIKE STEVENSON, MIKE STEVENSON Department of Epidemiology and Public Health, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorAIDAN P COSGROVE, AIDAN P COSGROVE Gait Analysis Service, Belfast Health and Social Care Trust, Musgrave Park Hospital, Stockman's Lane, Belfast, Northern Ireland.Search for more papers by this author CLAIRE KERR, CLAIRE KERR School of Nursing and Midwifery, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorBRONA C MCDOWELL, BRONA C MCDOWELL Gait Analysis Service, Belfast Health and Social Care Trust, Musgrave Park Hospital, Stockman's Lane, Belfast, Northern Ireland.Search for more papers by this authorJACKIE PARKES, JACKIE PARKES School of Nursing and Midwifery, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorMIKE STEVENSON, MIKE STEVENSON Department of Epidemiology and Public Health, Queen's University Belfast, Belfast, Northern Ireland.Search for more papers by this authorAIDAN P COSGROVE, AIDAN P COSGROVE Gait Analysis Service, Belfast Health and Social Care Trust, Musgrave Park Hospital, Stockman's Lane, Belfast, Northern Ireland.Search for more papers by this author First published: 28 September 2010 https://doi.org/10.1111/j.1469-8749.2010.03795.xCitations: 55 Dr Claire Kerr at Nursing and Midwifery Research Unit, Queen's University Belfast, 10 Malone Road, Belfast BT9 5BN, Northern Ireland. E-mail: [email protected] AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract Aim The aim of this study was to use a prospective longitudinal study to describe age-related trends in energy efficiency during gait, activity, and participation in ambulatory children with cerebral palsy (CP). Method Gross Motor Function Measure (GMFM), Paediatric Evaluation of Disability Inventory (PEDI), and Lifestyle Assessment Questionnaire-Cerebral Palsy (LAQ-CP) scores, and energy efficiency (oxygen cost) during gait were assessed in representative sample of 184 children (112 male; 72 female; mean age 10y 9mo; range 4–16y) with CP. Ninety-four children had unilateral spastic CP, 84 bilateral spastic CP, and six had other forms of CP. Fifty-seven were classified as Gross Motor Function Classification System (GMFCS) level I, 91 as level II, 22 as level III, and 14 as level IV). Assessments were carried out on two occasions (visit 1 and visit 2) separated by an interval of 2 years and 7 months. A total of 157 participants returned for reassessment. Results Significant improvements in mean raw scores for GMFM, PEDI, and LAQ-CP were recorded; however, mean raw oxygen cost deteriorated over time. Age-related trends revealed gait to be most inefficient at the age of 12 years, but GMFM scores continued to improve until the age of 13 years, and two PEDI subscales to age 14 years, before deteriorating (p<0.05). Baseline score was consistently the single greatest predictor of visit 2 score. Substantial agreement in GMFCS ratings over time was achieved (κlw=0.74–0.76). Interpretation These findings have implications in terms of optimal provision and delivery of services for young people with CP to maximize physical capabilities and maintain functional skills into adulthood. Abbreviations GMFM Gross Motor Function Measure LAQ-CP Lifestyle Assessment Questionnaire-Cerebral Palsy PEDI Paediatric Evaluation of Disability Inventory PEDI CAS PEDI caregiver assistance scaled scores What this paper adds • Longitudinal population-based trends have been found in energy efficiency, activity, and participation in children with ambulatory CP. • Evidence supports the fact that there is a decline in motor function from puberty onwards. • Our results indicate that participation is stable throughout childhood and the adolescent years. • This study confirms that GMFCS levels in children with CP remain stable over time. Cerebral palsy (CP) is the leading cause of motor impairment in childhood, caused by damage to, or malformation of, the developing brain.1 Although the brain 'lesion' is static, its consequences may change as the child develops, necessitating a lifelong demand on therapy services in some cases. Knowledge of the 'natural' progression of the condition may help families, service planners, and researchers to anticipate the likely future needs of this population. The most reliable data about the numbers of people affected by CP in developed countries come from case registers, the aims of which are to systematically compile data that can be used for surveillance and service planning and to provide a framework for research.2 The data collected are primarily of an epidemiological nature and provide a useful starting point for the development of more precise clinical research. Several large retrospective population-based studies have contributed to the knowledge-base of the long-term profile of people with CP. For example, Wu et al.3 investigated prognostic factors for ambulation and Day et al.4 studied changes in ambulatory status through adolescence and young adulthood. The prognostic charts resulting from these two studies provide useful age estimates for the achievement and retention of ambulatory skills. More recently, several prospective longitudinal studies have been reported. The Ontario Motor Growth Study5 mapped motor development in children with CP using the using the Gross Motor Function Measure (GMFM)6,7 and the Gross Motor Function Classification System (GMFCS).8 The resultant prognostic curves have been widely utilized by clinicians and researchers. A continuation of this study is currently in progress.9 Another study employed cross-sectional and longitudinal analyses to construct population-based gross motor developmental curves for children aged up to 15 years with hemiplegia and diplegia.10 Furthermore, prospective longitudinal work from the Shriners Group of Hospitals11 and from the Paediatric Rehabilitation in the Netherlands programme (PERRIN)12,13 is contributing to a more comprehensive picture of the young person with CP. The aims of this paper are to describe the 'natural progression' of the ambulatory form of CP over time and to identify predictors of change. A comprehensive assessment framework was used, of which selected measures of energy efficiency during gait, activity, and participation are presented in this article. Method Ethical approval Approval for the study was granted from the local research ethics committee, and all parents (and children when possible) provided written informed consent. Study design This was a 5-year prospective longitudinal study, which used a population-based approach to the identification, approach, and recruitment of a representative sample of children with ambulatory CP. Participants All children with a diagnosis of 'early impairment CP' who could ambulate more than 10m independently (assistive devices permitted), who were born between 1 June 1987 and 1 June 1999, and who were alive and resident in Northern Ireland on 1 June 2003 were potentially eligible to participate. Information on the presumed timing of CP was available from the Northern Ireland Cerebral Palsy Register.14 Children who had undergone lower limb surgery within the previous year or had received a botulinum toxin A injection to the lower limbs within the previous 6 months were excluded; however, appointments were scheduled over the data collection period in order to minimize exclusions for these reasons. The Northern Ireland Cerebral Palsy Register identified 487 potentially eligible participants, of whom a representative sample of 184 (38%) were recruited to the study. Families were contacted either by their child's orthopaedic surgeon (n=312) or by a community paediatric professional (n=175). More families responded to an invitation from the orthopaedic service than to invitations from the community professionals, but overall no evidence existed of any systematic biases in demographic or key clinical characteristics between those children who participated and those who did not. Full details of the recruitment process and associated analyses are provided elsewhere.15 Measurement tools Energy efficiency during gait was assessed using an oxygen consumption protocol and was recorded by a portable Cosmed K4b2 device (Cosmed, Rome, Italy). Participants had not eaten for 2 hours before the test and wore their normal footwear, orthotic devices, and/or assistive devices (if any). The test involved a 5-minute walking protocol, described comprehensively elsewhere.16 Resting oxygen rate during the final 2 minutes of an initial rest period, walking oxygen rate during the final minute of the walk period, and mean walking speed during the final minute of the walk period were calculated. Gross motor function was evaluated using the GMFM.7 Children were assessed barefoot using the original 88-item instrument. Children were also classified using the GMFCS.8 Participants aged over 12 years were classified using the GMFCS 6 to 12 years descriptors as the criteria for older children were not available at the time of assessment. Functional capabilities and the amount of caregiver assistance required in the areas of self-care, mobility, and social function were recorded using the Paediatric Evaluation of Disability Inventory (PEDI).17 The PEDI is primarily designed for the functional evaluation of children aged from 6 months to 7 years 6 months, but can be used with older children if their functional abilities are less than those expected of a typically developing child aged 7 years and 6 months.17 A research assistant completed the PEDI by interviewing the child's parent/carer. The impact of the child's disability on both the child and family unit was assessed using the Lifestyle Assessment Questionnaire-Cerebral Palsy (LAQ-CP).18 This questionnaire addresses physical independence, clinical burden, mobility, economic burden, social integration, and schooling, and was completed by the child's parent/carer. Definitions CP and clinical subtypes were defined according to the Surveillance of Cerebral Palsy in Europe guidelines.1 Early impairment CP was defined as motor impairment secondary to damage to the developing brain before the end of the neonatal period (i.e. within the first 28d after birth). Intellectual impairment was defined as moderate where the IQ (or best clinical estimate) was 50 to 70 and severe where the IQ was less than 50. Deprivation was defined using the Carstairs Index.19 Children were assigned to a deprivation quintile ranging from quintile 1 (least deprived) to quintile 5 (most deprived) based on their electoral ward of residence. Perceptual problems, rated by parents, related to depth and spatial perception only. For clarity of description the following terms are used in this paper: energy efficiency refers to the net oxygen cost of walking; activity refers to GMFM and PEDI scores, with GMFM reflecting capacity (what the child can do in a standardized environment) and PEDI reflecting performance (what the child actually does in their own environment); and participation refers to the LAQ-CP score. It is of note that the LAQ-CP is not a pure measure of participation, but was the best available tool at commencement of this study. Procedure Participants attended a regional hospital-based gait analysis laboratory on two occasions approximately 2 years 7 months apart. The same battery of physical and psychosocial tests were completed on each visit and were administered by the same research physiotherapist/research assistant. Assessments lasted from 2.5 to 3.5 hours. During an initial interview, caregivers subjectively rated their child's vision, hearing, perception, communication, and concentration as none, mild, moderate, or severe in addition to discussing aspects of the child's health care. Participants then underwent the oxygen consumption protocol while their caregiver completed the LAQ-CP. Afterwards, a research physiotherapist carried out the GMFM assessment while a research assistant interviewed the child's caregiver with the PEDI. GMFCS ratings were independently obtained at the time of assessment from the child's caregiver and the research physiotherapist. A third GMFCS rating was obtained, by mail, from the child's community physiotherapist. Epidemiological data relating to the child's IQ and seizure activity were obtained from the Northern Ireland Cerebral Palsy Register. Data analysis Data were initially reviewed descriptively and then analysed for differences between assessment points. Trends associated with ageing were then identified and explored in the context of preselected clinical variables. Data were analysed using SPSS version 17.0 (SPSS Inc., Chicago, IL, USA) and Stata version 9.1 (StataCorp LP, TX, USA). Continuous data were summarized using means and SDs. Categorical variables were summarized using frequency tables. The net oxygen cost was calculated as follows: Net O2 cost=(walking O2 rate−resting O2 rate)/average walking speed. Paired t-tests were used to establish if significant differences existed between visit 1 and visit 2 data on each of the measurement tools. Difference scores were then calculated for all the measurement tools (visit 2 score–visit 1 score) and their distribution was checked by observation of P–P plots. Difference scores were subjected to simple linear regression (by least squares) to determine if significant age-related trends were evident. If significant age-related trends were identified, multiple linear regression was then performed to determine which preselected clinical variables contributed significantly to the model. In each instance the visit 2 score was the dependent variable, with baseline score and age assigned as covariates. The role of the following preselected clinical variables was investigated: sex, CP type, incidence of orthopaedic surgery between assessment points, GMFCS level, IQ, incidence of seizures, and impairments of perception and concentration. For the purpose of the analyses, all fixed factors were dichotomized with the exception of the GMFCS, in which the following distinctions were made: (i) level I, (ii) level II, and (iii) levels III and IV. This analysis was checked by the bootstrap method (using 1000 iterations) to estimate confidence intervals (CIs). Stability of the GMFCS over time was determined by compiling cross-tabulations and then using the kappa statistic with linear weighting (κlw). The strength of agreement was defined as moderate, substantial, and almost perfect (κlw=0.41–0.60, 0.61–0.80, and 0.81–1.0 respectively).20 Finally, bias analysis was undertaken to test for heterogeneity in proportions (χ2 test) in characteristics of children who attended visit 1 but did not attend visit 2. In all analyses, two-tailed significance tests were employed, with the threshold of significance being 5%. Furthermore, missing data were not replaced; casewise deletion was simply applied. Results Demographics and clinical characteristics Of the initial 184 children assessed, 94 had unilateral spastic CP (51%), 84 (46%) had bilateral spastic CP, and six children had non-spastic forms (four had ataxia, one had dyskinesia, and one had hypotonia). A total of 151 children returned for the second assessment, with the parents of a further six children providing questionnaire data by post, giving a second response rate of 86% (n=157). Twenty-four children underwent surgery during the interim period. Subsequently, one child was excluded from all analyses owing to a change in diagnosis between the assessments. There were no statistically significant differences between those who re-attended (n=157) and those who did not (n=26) in terms of age, sex, deprivation quintile, GMFCS level, or associated impairments. The mean time between assessments was 2 years 7 months (SD 2mo). The GMFCS distribution of participants and clinical characteristics are detailed in Table I. Table I. Demographic data Visit 1, mean (SD) Visit 2, mean (SD) n 184 157 (86%) Sex (M:F) 112:72 99:58 Age (y) 10.8 (3.6) 13.3 (3.5) Age range (y) 4.6–17.5 7.1–19.9 Height (m) 1.4 (0.2) 1.5 (0.2) Weight (kg) 38.8 (16.9) 48.1 (17.3) GMFCS Level I 57 (31%) 55 (35%) Level II 91 (49.5%) 70 (44.5%) Level III 22 (12%) 16 (10%) Level IV 14 (7.5%) 10 (6.5%) Missing 6 (4%) SCPE classification Unilateral spastic 94 82 Bilateral spastic 84 70 Other 6 5 M, male; F, female; GMFCS, Gross Motor Function Classification System; SCPE, Surveillance Of Cerebral Palsy in Europe. Data distribution Although ceiling effects in raw scores on the PEDI and, to a lesser extent, the GMFM were observed, the difference scores for these measures followed a normal distribution as evidenced by visual inspection of the P–P plots. Changes over time Statistically significant differences in raw scores on all of the measurement tools were noted between the first and second assessments. Increases in mean GMFM and PEDI scores were recorded, indicating improvements in abilities (p=0.004 for GMFM; p≤0.001 for all PEDI subscales). Similarly, improvement in participation over time was reflected by a decrease in the mean LAQ-CP score (p<0.001). In contrast, an increased cost of walking was noted by the increase in the mean net oxygen cost difference score over time (p=0.017). Mean scores at each assessment and difference scores on all measurement tools for those children with data available at each time point are presented in Table II. Table II. Mean (SD) scores on measurement tools for all participants (data available at both assessment points) Visit 1 2003/05, mean (SD) Visit 2 2006/07, mean (SD) Mean difference score (SD) visit 2–visit 1 95% CI of the difference Clinical implication Net oxygen cost of walking (n=85) 0.188 (0.105) 0.204 (0.110) 0.017 (0.049) 0.005–0.046 Deterioration GMFM-66 (n=121) 78.43 (14.18) 80.24 (14.35) 1.81 (6.73) 0.60–3.02 Improvement PEDI (n=142) Functional scaled score Self-care 74.70 (14.20) 81.36 (15.41) 6.66 (9.71) 5.05–8.27 Improvement Mobility 78.26 (15.59) 84.26 (15.25) 6.00 (9.95) 4.35–7.65 Improvement Social function 79.56 (15.56) 84.53 (15.78) 4.96 (11.61) 3.04–6.89 Improvement Caregiver assistance scaled score Self-care 75.79 (17.01) 83.10 (15.92) 7.31 (11.17) 5.45–9.16 Improvement Mobility 82.62 (15.48) 87.68 (13.91) 5.05 (10.75) 3.27–6.84 Improvement Social function 90.44 (15.28) 93.60 (14.38) 3.17 (10.99) 1.34–4.99 Improvement LAQ-CP (n=148) 32.87 (14.99) 28.48 (15.00) −4.39 (9.51) −5.93 to −2.84 Improvement GMFM-66, Gross Motor Function Measure-66; PEDI, Paediatric Evaluation of Disability Inventory; LAQ-CP, Lifestyle Assessment Questionnaire-Cerebral Palsy. Age-related trends Regression analyses using the difference scores for each measurement tool and the age at first assessment revealed that net oxygen cost, GMFM, and the PEDI caregiver assistance scale (PEDI CAS) scores for mobility and social function altered significantly over time (see Table III), although in all instances very weak relationships were identified. The relationship between the net oxygen cost and age was best described by a quadratic model (r=0.079; F2,82=3.45; p=0.035), with the turning point of the curve occurring at approximately 12 years of age, suggesting that gait is least efficient at this age. Table III. Regression analyses results: measurement tool difference score as dependent variable, age at first assessment as independent variable. Statistically significant models are shown in bold Measurement tool r Model F (df,n) p-value Net oxygen cost of walking 0.079 Quadratic 3.50 (2,82) 0.04 GMFM-66 0.146 Linear 20.37 (1,119) <0.001 PEDI Functional scaled score Self-care 0.004 Linear 0.53(1,140) 0.47 Mobility 0.018 Linear 2.55(1,140) 0.11 Social function 0.013 Linear 1.86(1,140) 0.18 Caregiver assistance scaled score Self-care 0.017 Linear 2.42(1,140) 0.12 Mobility 0.071 Linear 10.67 (1,140) 0.001 Social function 0.028 Logarithmic 4.86 (1,140) 0.03 LAQ-CP 0.034 Quadratic 2.57(2,145) 0.08 GMFM-66, gross motor function measure-66; PEDI, paediatric evaluation of disability inventory; LAQ-CP, lifestyle assessment questionnaire-cerebral palsy. A linear relationship was identified between GMFM-66 and age (r=0.146; F1,119=20.37; p<0.001), with increasing age being associated with decreasing motor abilities. Figure S1 (online supplementary material) shows that the rate of development of motor skills is greatest in younger children, but this rate slows linearly until a position of 'no change' is achieved at approximately 13 years of age (95% CI 11.9–16.3y). Beyond age 13, deterioration in motor abilities was noted. A similar deteriorating linear trend was identified for PEDI CAS mobility (r=0.071; F1,140=10.67; p=0.001), with increased dependence on assistance from caregivers noted from the age of 14 years. Finally, a very weak deteriorating logarithmic relationship was identified between PEDI CAS social function and age (r=0.028; F1,140=4.86; p=0.029). Other contributing variables Multiple linear regression was carried out for those measures that demonstrated statistically significant age-related trends. Results were checked by the bootstrap method. The results are summarized in Table SI (online supplementary material). The visit 2 net oxygen cost score was significantly dependent on baseline net oxygen cost score, surgery, IQ, concentration, and GMFCS level. This was confirmed by the bootstrap method, with the exception of the role of GMFCS (p=0.051). As demonstrated in Table SI, baseline oxygen cost was the greatest predictor of the visit 2 score (p<0.001). Better visit 2 net oxygen cost scores (i.e. lower scores) were also associated with an IQ over 70 (p=0.005), having surgery between the study assessment points (p=0.012), poorer concentration (p=0.005), and being classified as GMFCS level I compared with GMFCS levels III and IV (p=0.030). Baseline score was also the most influential factor on the second GMFM score (p<0.001), with GMFCS level, age, and perception also significantly contributing. However, results from the bootstrap method differed slightly in that the GMFCS level was not considered to be a significant variable (p=0.057–0.087) and that seizure activity was a more likely contributor (p=0.033). If applying the regression model, those children who could ambulate unaided were likely to have better second visit GMFM scores than those who required walking aids (GMFCS level I compared with levels III and IV; p=0.029). GMFM scores tended to deteriorate less quickly in younger children (p=0.001) and in children who had a moderate to severe perceptual problem (p=0.012). Full agreement between the regression and bootstrap methods was evident in the analyses of both PEDI subscales. Only baseline score and GMFCS level were shown to contribute significantly to the PEDI CAS mobility visit 2 score, with lower GMFCS levels resulting in poorer PEDI CAS mobility scores (GMFCS level I compared with levels III and IV; p=0.034). Factors that significantly affected the visit 2 PEDI CAS social function score were baseline score, incidence of orthopaedic surgery between assessments, IQ, and concentration. Unsurprisingly, baseline score was again the greatest predictor (p<0.001). Improved visit 2 PEDI CAS social function scores were associated uniquely with an IQ over 70 (p=0.002), no/mild concentration problems (p=0.014), and having orthopaedic surgery between the assessments (p=0.006). Stability of the GMFCS over time Substantial agreement in GMFCS level was noted over the 2 years 7 month assessment period, as indicated by κlw values of 0.74 to 0.76 and detailed in Table IV. This stability was noted with all three assessors: parents, clinical physiotherapist, and research physiotherapist. Table IV. Stability of Gross Motor Function Classification System ratings over two assessments, 2 years and 6 months apart Rater n % Absolute agreement κlw 95% CI Parent 150 80 0.74 0.65–0.83 Clinical physiotherapist 92 76 0.74 0.63–0.84 Research physiotherapist 151 79 0.76 0.68–0.84 κlw, linear weighted kappa; CI, confidence interval. Discussion This study presents age-related trends in oxygen cost, activity, and participation in a representative sample of children with CP. Significant improvements in raw scores for activity (GMFM and PEDI) and participation (LAQ-CP) were noted in the sample over two time points, 2 years 7 months apart. However, this trend was not mirrored by the participants' energy expenditure during gait, as a statistically significant deterioration in the mean raw net oxygen cost was noted over time. Interestingly, very weak relationships with age were detected, with relationships between age and net oxygen cost, GMFM, PEDI CAS mobility, and PEDI CAS social function scores achieving statistical significance. The role of multiple covariates was investigated for those measures demonstrating age-related changes in an attempt to quantify predictor variables. Of the proposed predictors, GMFCS level, IQ, perception, concentration, incidence of surgery between visits, age, presence of seizures, and baseline score in the measurement tool under investigation were shown to be influential. Furthermore, considerable stability in parent and therapist rating of GMFCS level over the assessment period was also demonstrated. The quadratic relationship associated with the age-related trend in energy efficiency suggests that gait is most inefficient at around 12 years of age. Whilst perhaps contrary to clinical intuition, it may be that walking efficiency deteriorates with the onset of puberty and changing demands of the child's education. The incidence of surgery between visits, IQ, and concentration were noted to influence this model; however, baseline oxygen cost was identified as the greatest predictor of the visit 2 score, accounting for 69% of its variance. Contrary to these findings, Day et al.4 reported an overall picture of stability in ambulation during adolescence and young adulthood, although other authors have documented a decline in ambulatory ability in adults with CP.21–23 When selecting energy efficiency variables, we elected to continue using net oxygen cost as our main analysis variable instead of the more recently advocated net non-dimensional oxygen cost.24 The reasons for this were twofold: firstly, to maintain consistency with reporting over time16 and, secondly, rendering the net oxygen cost data dimensionless simply required multiplication by a constant (20.1/g) and thus would not have any effect on the statistical analysis. More detailed investigation of the longitudinal profile of energy efficiency of walking in this sample is warranted but is beyond the scope of this paper. A weak linear trend reflecting a decrease in activity (GMFM) with increasing age was observed, with children classified as GMFCS level I tending to deteriorate less rapidly than those classified as level III or IV. This concurs in part with the findings of Voorman et al.12 and Hanna and colleagues.9 Van Eck et al.13 reported declines in motor performance for children classified as GMFCS level II, IV, or V, but speculated that this anomaly in the hypothesized trend (decreasing function with increasing GMFCS level) may be due to intellectual or fine motor abilities. Somewhat counterintuitively, the current study also revealed that loss of motor function was slower among children with moderate to severe perceptual problems (as rated by parents) than among their peers with no or mild perceptual difficulties. This may be due to an increased focus on retention of motor skills or accommodation to perceptual difficulty over time, or indeed the finding may simply be spurious because of the lack of objectivity in our measurement of perception. Interestingly, the two statistical methods differed slightly when predicting the GMFM score for visit 2, with the GMFCS level just approaching statistical significance in the bootstrap model (p=0.057) and seizure activity approaching statistical significance in the regression model (p=0.067). Other authors have shown age, intellectual impairment, epilepsy, GMFCS level, manual ability, and selective motor control to be significant predictors of gross motor function.12,25–27 Significant age-rel
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