Reliability and patient-centered feasibility of the Gross Motor Function Measure in children diagnosed with central...

Children diagnosed with central nervous system (CNS) tumors frequently present with persistent motor impairments that compromise independence and participation. Although the Gross Motor Function Measure (GMFM-88) is widely used in pediatric neurology, evidence regarding its reliability and feasibility in pediatric neuro-oncology remains limited. Therefore, this study aimed to investigate the intra- and inter-rater reliability of the GMFM-88, its association with tumor volume, and evaluate the patient-centered clinical feasibility of the instrument.

This cross-sectional reliability study was conducted at a specialized cancer rehabilitation center. Participants were children with brain tumors confirmed by imaging and biopsy. Gross motor function was assessed using the GMFM-88 with all assessments video-recorded following a standardized protocol. Primary outcomes were intra- and inter-rater reliability. Intra-rater reliability was determined through the analysis of the video of the evaluation day, by the same rater after a four-week interval. Inter-rater reliability was assessed by a second, independent blinded rater who scored the same video recordings. Reliability was analyzed using intraclass correlation coefficients (ICC; two-way mixed-effects, absolute agreement). Secondary outcomes included the correlation between GMFM-88 total scores and tumor volume estimated via the ellipsoid method. To investigate the relationship between variables, Pearson's correlation coefficient was calculated. Furthermore, patient-centered clinical feasibility was assessed using a 7-point Likert scale addressing safety, administration speed, and acceptability.

Thirty-two children were included (mean age 10.2 ± 3.7 years; 50% female). The GMFM-88 demonstrated excellent reliability, with an intra-rater ICC of 0.997 (95% CI: 0.993-0.998) and an inter-rater ICC of 0.999 (95% CI: 0.998-0.999). No significant association was observed between tumor volume and GMFM-88 total scores (r = 0.085; 95% CI: -0.27 to 0.42; p = .64). Feasibility ratings were high for safety (aggregate score 76/96) and acceptability (91/96), though administration speed was variable (64/96).

The GMFM-88 is a highly reliable and clinically applicable tool for assessing gross motor function in pediatric neuro-oncology. The lack of correlation between tumor size and motor capacity suggests that functional outcomes may be more closely related to lesion topography in eloquent areas than volume alone. Major limitations include the single-center design and small sample size. However, these findings support its use as a standardized and clinically applicable outcome measure in pediatric neuro-oncological.