of eye abnormalities are also common, such as one eye being smaller than normal (microphthalmia), changes in the optic nerve, and incomplete closure/slitting of the membranes of the eye (coloboma). Rapid, involuntary eye movements (nystagmus) are common. Since girls with Aicardi syndrome have an intellectual disability that makes it difficult to participate in an eye examination, it is difficult to measure vision accurately. Problems from the gastrointestinal tract are common, for example constipation, diarrhea and that the normal valve mechanism between the stomach and the esophagus (upper mouth of the stomach) does not work normally and the stomach contents therefore leak up into the esophagus (gastroesophageal reflux). Some may also have difficulty eating. Some of the girls enter puberty earlier than normal, but delayed puberty has also been described. Drooling and teeth grinding is common. Extra ribs or lack of ribs and vertebral deformities often occur. While growing up, several of the girls get a crooked back (scoliosis). There are reports of isolated cases of tumors, especially brain tumors. Aicardi syndrome is a non-progressive condition and in itself does not lead to any deterioration, but various complications mean that there is an increased mortality among girls with the syndrome. Very little is known about the long-term prognosis, but there are occasional reports that the epilepsy may become milder with increasing age. The oldest women with the syndrome described so far are in their 40s. A number of tumors have been reported in association with Aicardi syndrome: choroid plexus papilloma (the most common), medulloblastoma, gastric hyperplastic polyps, rectal polyps, soft palate benign teratoma, hepatoblastoma, parapharyngeal embryonal cell cancer, limb angiosarcoma and scalp lipoma. Genetics The syndrome is probably caused by a change (mutation) in one or more genes on the short arm of the X chromosome (Xp22), but which gene or genes are mutated is not yet (2015) known. Male fetuses with this change are unlikely to survive, which is because they only have one X chromosome. The individual boys with the syndrome described have also had the sex chromosome abnormality XXY syndrome (Klinefelter syndrome). Girls, who have two X chromosomes, can be born with the syndrome, because their second (normal) X chromosome compensates to some extent for the mutated gene. The mutation leads to a characteristic malformation of the brain stem with a complete absence the corpus callosum. As a rule, there are also signs that groups of brain cells