Impaired balancing ability in dyslexic children.

Children with developmental dyslexia struggle to learn to read and spell despite adequate intelligence and educational opportunity. Several lines of research are attempting to establish the neurobiological basis of dyslexia, and low-level sensory and motor deficits have been found in dyslexic populations; furthermore, behavioural and imaging data point to cerebellar dysfunction in dyslexia. To investigate this, normal readers (n=19) and children with developmental dyslexia (n=16) were asked to perform various cognitive, literacy, and balancing tasks. Children balanced on the left or right foot, with eyes open or closed, for a period of 10 s during which their movements were recorded with a motion-tracking system. Dyslexic children were less stable than the control children in both eyes-open conditions (left foot P=0.02, right foot P=0.012). While there were no group differences during the eyes-closed conditions, the dyslexic children dropped a foot to correct balance significantly more often than control children (P<0.05). Incidence analysis showed that 50% of the dyslexic group fell into the 'impaired' category on the eyes-open balancing tasks; when the mean balancing scores and the foot drops were considered, only three of our dyslexic children showed no evidence of balancing difficulties. There were strong correlations between reading and spelling scores and the mean eyes-open balancing score (r=0.52 and 0.44, respectively). Thus, while not all children with developmental dyslexia show impaired balancing skills, low-level motor dysfunction may be associated with impaired literacy development. This could be due to several factors, including the involvement of the cerebellum, the magnocellular system, or more general developmental immaturity.