Dylexia in children and young adults: three independent neuropsychological syndromes.

In an attempt to delineate causal factors in dyslexia, 113 children and young adults (age-range eight to 18 years) were divided into three groups: those with brain damage who could read (n=31), those with brain damage who were dyslexic (n=53), and those without brain damage who were dyslexic (n=29). A battery of neuropsychological tests was presented to each participant. No significant differences were found between the two dyslexic groups. Three syndromes--language disorder, articulation and graphomotor dysco-ordination, and visuo-perceptual disorder--were found among the great majority of those with dyslexia. The results support a model of dyslexia as being caused by multiple independent defects in higher cortical functioning, as opposed to the theory of a single causal defect. A clinical description of each syndrome is given and models of dyslexia are discussed. The authors stress the desirability of including brain-damaged readers as a control group in any future study on causal factors in dyslexia.