DYSLEXIA AND CORPUS-CALLOSUM MORPHOLOGY

Objective: There is evolving evidence that developmental dyslexia is a ssociated with anomalous cerebral morphology in the bilateral frontal and left temporoparietal regions. This study examined the morphology o f the corpus callosum, as possible deviations in other important struc tures are poorly understood in this behaviorally diagnosed syndrome. D esign: Magnetic resonance imaging scans were obtained from children wi th developmental dyslexia and from matched control children. Morphomet ric measurements were examined to determine if regional differences ex isted in the corpus callosum between these two groups of children. Set ting: Magnetic resonance imaging studies were completed at Athens (Ga) Magnetic Imaging. Patients and Other Participants: Sixteen developmen tal dyslexic children (mean age, 9.7 years) and a matched sample of ch ildren who were diagnosed as being normal were examined by using a rel iable comprehensive diagnostic process. Main Outcome Measures: Using a midsagittal magnetic resonance imaging scan, corpus callosum morpholo gy was evaluated by segmenting the corpus callosum into five regions o f interest. Results: Analysis of the corpus callosum revealed that the anterior region of interest (the genu) was significantly smaller in t he dyslexic children. Significant correlations existed between reading achievement and the region-of-interest measurements for the genu and splenium. Measured intelligence, chronologic age, and gender were not related to region-of-interest measurements of the corpus callosum. Con sistent with previous studies, the dyslexic individuals were character ized by significant psychiatric comorbidity, particularly attention-de ficit disorder with and without hyperactivity. Reported familial left- handedness also distinguished the dyslexic children. Conclusions: Subt le neurodevelopmental variation in the morphology of the corpus callos um may be associated with the difficulty that dyslexic children experi ence in reading and on tasks involving interhemispheric transfer.