Normal interhemispheric visual transfer with incomplete section of the splenium

During the removal of a ruptured arteriovenous malformation, a young man underwent partial sectioning of the splenium of the corpus callosum. Postoperative testing showed no deficit to interhemispheric visual or auditory transfer. To understand the extent of the splenial section, we cut ten normal brains in the sagittal plane and analyzed the shape of the splenium. It may be markedly curved or bulbous. Our findings lead us to conclude that a small band of ventral splenial fibers may be adequate to allow a patient to perform normally on tachistoscopic testing. Unless there is postmortem proof of complete spenial section, it may not be justified to invoke nonsplenial mechanisms to explain preservation of interhemispheric visual transfer in human surgical cases.