Recovery from hemialexia.

Hemialexia is believed to be caused by the lesion of the splenium of the corpus callosum. However, no previous reports conclusively demonstrated that the hemialexic had the splenial lesion. A right-handed male with hemialexia who was presumed to have the splenium sectioned for a partial removal of a pineal tumor was examined with magnetic resonance imaging. The sagittal and coronal imagings clearly showed that his splenium was not present. The hemialexic had partially recovered at 9 years after the onset. The patient was 76% correct in Japanese phonogram words and 92% correct in ideogram words in an interfield same-different judgment, that is, judging whether 2 one-letter words, one in the left hemifield and the other in the right, were the same or different. Consequently, the possible mechanism for the recovery is that the transfer of visual word information from the right hemisphere to the left has been partially achieved by commissural fibers other than those of the splenium. Information from phonogram words in the right hemisphere is probably less transferred to the left hemisphere than that from ideogram words. The results also suggested that when the transfer of word information in the right hemisphere to the left is interfered with, the left hemisphere tends to mistake the same pair of words for the different pair.