Abstract
Autism (ASD), attention deficit/hyperactive disorders (ADHD), and dyslexia (DYS) are defined in DSM-5 as neurodevelopment disorders (NDDs) and several times they are comorbid disorders. Several studies have reported poor oculomotor performance and postural instability in this population of children confirming the cerebellar deficit hypothesis in subjects with NDDs. In this paper, we summarized oculomotor and posture findings collected over the last decade, in order to find out biomarkers for children with NDDs; To our knowledge, such issue has never been studied before; the present study is designed to fill this gap. Oculomotor parameters (the number of express and anticipate saccades, the number of saccades during fixations and the number of catch-up saccades during pursuits), and the postural instability index measured in two viewing conditions (eyes open and eyes closed, on stable and unstable platform) were compared in four groups of 40 children. One-way ANOVA reported significant differences in oculomotor parameters between the three groups of children with NDDs with respect to a typical developing (TD) children group: the number of anticipatory saccades was found to be significantly (p < 0.001) higher in the ADHD (32.4 ± 5.9) and the DYS (34.7 ± 5.3) groups; the occurrence of express saccades and catch-up saccades was significantly (p < 0.001) more frequent in the ASD group (26.8 ± 1.8 and 55.3 ± 4.2, respectively); unwanted saccades occurred more in ADHD (8.5 ± 0.7) and DYS (7.3 ± 1.1) groups. In the fixation with distractor task, the number of saccades was significantly (p < 0.001) higher in the ADHD group (36.3 ± 3.9). In addition, the mixed repeated ANOVA on the postural instability index (measured under eyes open and eyes closed conditions, on stable and unstable platforms) reported a significant difference (p < 0.001) in such parameters in children with NDDs (ASD: 2.8 ± 0.6; DYS: 2.6 ± 0.5; ADHD: 2.7 ± 0.5, respectively) with respect to the TD group (1.9 ± 0.3); however, the postural instability index failed to distinguish between the different neurodevelopmental deficits. Such abnormal oculomotor and postural performances are in line with poor cerebellar activity; oculomotor measures only could be used as phenotype biomarkers for children with NDDs. Finally, these results could be useful to clinicians looking to develop specific oculomotor and/or postural training programs based on visual fixations and body stability exercises designed to reinforce motor ability in children with NDDs.