Corpus callosum morphology was studied by MRI in 16 children (mean age, 9.7 yrs) with developmental dyslexia and matched controls at the Center for Clinical and Developmental Neuropsychology, University of Georgia, Athens, and the Department of Neurology, Medical College of Georgia, Augusta, and the Athens Magnetic Imaging. The genu of the corpus callosum was significantly smaller in the dyslexic children. Familial left-handedness, and ADD with and without hyperactivity distinguished the dyslexic children from controls. 
COMMENT. Studies of MRI morphology of the corpus callosum in monozygotic twins at Dartmouth Medical School Program in Cognitive Neuroscience showed wide variations in size and shape of the human corpus callosum. Measurements revealed greater similarity in twin pairs than in randomly paired controls . The anatomy of the corpus callosum appears to be under genetic control as well as being influenced by nongenetic factors. How much this natural variation in size of the corpus callosum influenced the results of the above study in dyslexia is debatable. (see Progress in Pediatric Neurology I, PNB Publ, 1991, pp 168-9).