Neurosurgery and the anatomy of reading: a practical review.

Tumors and vascular malformations in the posterior parts of the dominant hemisphere are frequently associated with preoperative alexias, and surgical maneuvers in these areas may cause the appearance of this neurobehavioral deficit as an operative complication. Lesions of the dominant (left) angular gyrus are associated with the syndromes of alexia with agraphia. Alexia without agraphia results from lesions of the pathways which conduct visual information from the calcarine areas to the left angular gyrus (splenium of the corpus callosum, left lingual and fusiform gyri, left transverse and vertical occipital fasciculi). A brief bedside examination (outlined in the text) provides useful pre- and postoperative localizing information. Fresh cadaver studies of the brain in situ have shown that the approximate center of the left angular gyrus area is found by first locating a point 9 cm forward along the midline from the inion and then moving 4 1/4 cm laterally. These measurements define a point which is a few centimeters medial and posterior to the center of the parietal eminence.