Loss of the power to comprehend written materials despite preservation of the ability to write (i.e., alexia without agraphia). This condition is generally attributed to lesions that "disconnect" the visual cortex of the non-dominant hemisphere from language centers in the dominant hemisphere. This may occur when a dominant visual cortex injury is combined with underlying white matter lesions that involve crossing fibers from the occipital lobe of the opposite hemisphere. (From Adams et al., Principles of Neurology, 6th ed, p483).
