Dyslexia and corpus callosum morphology
G. W. Hynd, J. Hall, E. S. Novey, D. Eliopulos, K. Black, J. J. Gonzalez, J. E. Edmonds, C. Riccio and M. Cohen
Center for Clinical and Developmental Neuropsychology, University of Georgia, Athens.
OBJECTIVE: There is evolving evidence that developmental dyslexia is
associated with anomalous cerebral morphology in the bilateral frontal and
left temporoparietal regions. This study examined the morphology of the
corpus callosum, as possible deviations in other important structures are
poorly understood in this behaviorally diagnosed syndrome. DESIGN: Magnetic
resonance imaging scans were obtained from children with developmental
dyslexia and from matched control children. Morphometric measurements were
examined to determine if regional differences existed in the corpus
callosum between these two groups of children. SETTING: Magnetic resonance
imaging studies were completed at Athens (Ga) Magnetic Imaging. PATIENTS
AND OTHER PARTICIPANTS: Sixteen developmental dyslexic children (mean age,
9.7 years) and a matched sample of children who were diagnosed as being
normal were examined by using a reliable comprehensive diagnostic process.
MAIN OUTCOME MEASURES: Using a midsagittal magnetic resonance imaging scan,
corpus callosum morphology was evaluated by segmenting the corpus callosum
into five regions of interest. RESULTS: Analysis of the corpus callosum
revealed that the anterior region of interest (the genu) was significantly
smaller in the 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.
Consistent with previous studies, the dyslexic individuals were
characterized by significant psychiatric comorbidity, particularly
attention-deficit disorder with and without hyperactivity. Reported
familial left-handedness also distinguished the dyslexic children.
CONCLUSIONS: Subtle neurodevelopmental variation in the morphology of the
corpus callosum may be associated with the difficulty that dyslexic
children experience in reading and on tasks involving interhemispheric
transfer.
