Brain decompression surgery is performed when there is not enough room for the brain inside the skuIl. When there is not enough room this forces the brain to push below the skull opening (foramen magnum). The surgery is removes a small amount of bone to increase the opening of the foramen magnum. It may also include opening of the dura and sewing either a patch from a bovine or your own tissue. This is all done to create more room inside the skull for the brain. This condition is called Chiari Malfromation.