Developmental dyslexia. Evidence for a subgroup with a reversal of cerebral asymmetry.

The computerized brain tomograms of 24 patients with developmental dyslexia were analyzed for cerebral asymmetry. Ten patients showed a reversal of the pattern of asymmetry regularly observed in normal right-handed individuals so that the right parietooccipital region was wider than the left. The ten dyslexic patients with this reversal of cerebral asymmetry had a lower mean verbal IQ than the other 14 dyslexic patients in this study. The reversal of cerebral asymmetry that occurred in ten of the dyslexic patients may result in language lateralization to a cerebral hemisphere that is structurally less suited to support language function and thus act as a risk factor for the development of reading disability.