Cavernous malformations in the brain are collections of abnormally small blood vessels and bigger, stretched-out, thin-walled blood vessels packed with blood. Blood vessel abnormalities can also arise in the spinal cord, the brain’s covering (dura), or the skull’s nerves. Cavernous malformations range220 in size from a quarter of an inch to three to four inches. Blood can flow from cavernous malformations, causing bleeding in the brain or spinal cord (hemorrhage). Depending on where a cavernous malformation in a person’s nervous system is located, brain or spinal hemorrhages can cause a variety of more visible neurological symptoms. The cause of cerebral cavernous malformations is unknown. However, about 20% of persons with cerebral cavernous malformations have the familial form, which means they got the disease from their parents. In addition, researchers have discovered genetic abnormalities that cause cerebral cavernous malformations.