Spina bifida cystica: A bony defect in the vertebral column that causes a cleft in that column. The meningeal membranes that cover the spinal cord and part of the spinal cord protrude through this cleft, and are clearly visible. The opening can be surgically repaired, usually shortly after birth. Some children will also need treatment for related problems, such as hydrocephalus.

Also known as meningomyelocele.