Animal studies suggest that spatial skills are dependent on an intact septum pellucidum. This theory was tested by comparing patients who were visually impaired due to bilateral optic nerve hypoplasia: 13 with a septum pellucidum were compared with six children without a septum pellucidum. There was no difference in spatial ability. The finding of an absent septum pellucidum may only indicate the timing of a congenital brain insult, and it cannot be used to predict specific clinical, neuroendocrinological, cognitive or spatial abnormalities.