Multidimensional Motor Phenotype Characterization in Children with Joubert Syndrome: A Cross-Sectional Cohort Study

Background: Joubert syndrome (JS) is a rare neurodevelopmental ciliopathy characterized by cerebellar and brainstem malformation and heterogeneous motor outcomes. Although global developmental delay is well described, integrated clinical characterization combining functional and structural domains remains limited. The aim of this exploratory study was to describe a multidimensional motor phenotype in children with JS and to explore associations between selected functional and structural parameters. Methods: A prospective cross-sectional cohort study was conducted in 25 children with MRI-confirmed JS (aged 2-16 years). Gross motor performance was assessed using the GMFM-88, and postural control was evaluated with the modified Brief Ataxia Rating Scale (mBARS). Measured musculoskeletal parameters included joint range of motion and sacral slope as an indicator of sagittal pelvic alignment. Thoracoabdominal configuration was assessed using angular and anthropometric measurements. Associations between predefined functional and structural variables were explored using Spearman's rank correlation coefficients. Analyses were exploratory and hypothesis-generating and were not adjusted for multiple comparisons. Results: Marked inter-individual variability was observed across functional and structural domains. A moderate negative correlation was identified between GMFM-88 (Gross Motor Function Measure-88) and mBARS (modified Brief Ataxia Rating Scale) scores (ρ = -0.512, p-value = 0.007). Sacral slope demonstrated statistically significant associations with hip extension, ankle dorsiflexion, chest and abdominal circumference, and sternoclavicular alignment (all p-value < 0.05). No significant correlations were detected between gross motor performance and isolated structural parameters. Intra-rater reliability of selected measurements was high (ICC range 0.939-0.999). Conclusions: This exploratory, hypothesis-generating study demonstrates multidimensional variability in motor organization encompassing functional, postural, and structural domains. Gross motor performance appears more closely related to postural control than to isolated peripheral structural measures within this exploratory framework. Structural parameters exhibit internal statistical co-variation but do not independently determine functional capacity. These findings support the value of integrated multidomain physiotherapy assessment in rare cerebellar neurodevelopmental disorders.