In these children, hydrocephalus is caused by obstruction of the fourth ventricle due to its herniation into the spinal column.
2
More serious defects involving herniation of abdominal contents outside the infant's body are omphalocele and gastroschisis.
3
The surgery also appears to reverse hindbrain herniation, in which the back of the brain slips down into the spinal canal.
4
Type II malformation, sometimes called Arnold Chiari malformation, is more severe than Type I and involves herniation of a more significant part of the cerebellum, part of the fourth ventricle, and parts of the brain stem.
5
Type IV malformation consists of an underdevelopment of the cerebrum and involves no herniation of brain tissue into the spinal area.