Quantification of head motion in children with cerebral palsy when testing segmental trunk control

The development of objective assessment tools to complement subjective evaluations could have a major impact in the evaluation of the consequences of neuromotor disabilities, specifically in the assessment of trunk control in children with cerebral palsy (CP). Current assessments are subjective and typically assess the general control status of a child under unbalancing situations. Only the Segmental Assessment of Trunk Control (SATCo) evaluates static, active and reactive control at six discrete trunk segmental levels and free sitting to identify the topmost trunk segment where the child does not demonstrate control. The characteristics of the SATCo make it an ideal start point to generate an objective measurement tool of control. Motion of the head is one of the main characteristics observed during a SATCo to determine the child's segmental level of control. This pilot study measured head motion during a SATCo to determine if the measurement reflected the clinical observations. Three children with different degrees of neuromotor disability were tested using the SATCo while a video camera recorded sagittal plane movements. A Head segment was defined by markers on the ear tragus and temporal fossa in vertical line with the ear when the head was aligned. Head segmental angles were calculated in relation to a real vertical, and the cumulative displacement was normalised by time (deg·s-1). One segment where external support was provided high on the trunk (Upper-Thoracic, UT) and one where external support was at the pelvis i.e. low on the trunk (Lower-Lumbar, LL) were selected for the analysis. Overall, head motion values were larger for the lower trunk tests (LL) than for the tests at the higher segment (UT) with greater external support provided. The poorer lumbar control of Child 2 and Child 3 was demonstrated in both active (39.9°·s-1, 23.3°·s-1) and reactive tests (37.3°·s-1, 13.8°·s-1). The results also showed how increasing task complexity (static to reactive) and reducing the level of support (UT to LL), increased head motion in the presence of a neuromotor disability. The results presented here corroborated the clinical evaluation of the SATCo. Head motion will have small values when children with CP are tested at a trunk segmental level where control has already been learnt or where external support is provided; children with poorer lumbar control will have an increased head motion when testing is below their trunk segmental level of assured control. This video-based approach represents a step towards the development of an objective tool for the assessment of head/trunk control in children with CP.