n. a congenital herniation (protrusion) of the meninges (the three membranous layers that cover the brain and spinal cord) through an abnormal opening in the skull or spinal cord, with seepage of cerebrospinal fluid into the protrusion. The disorder is sometimes associated with hydrocephalus or other neurological defects, which reduces the chances of a favorable prognosis. If the herniation contains neural tissue, the condition is identified as an encephalocele.