A case of callosal agenesis with strong anatomical and functional asymmetries.

A 30-year-old right-handed man (W.D.) with total callosal agenesis was examined neuropsychologically and with magnetic resonance imaging. Basic neuropsychological testing revealed normal intelligence and average attentional capabilities. Anatomically, W.D. shows strong leftward perisylvian asymmetry both for the planum temporale and planum parietale, an unusual pattern not found in our database of more than 200 brains of young and healthy individuals. Functionally, W.D. has strong right hand superiority for hand skill and tactile object recognition, indicating unusual left hemisphere dominance for both functions. Our observations could support the hypothesis that callosal connectivity and hemispheric asymmetry may be inversely related.