A 1-year-old girl is brought to the clinic for a routine checkup. The child appears normal except for a dimpling of the skin in the lumbar region with a tuft of hair growing over the dimple. You reassure the mother that this condition is seen in 10% to 25% of births and normally has no ill effects. What is this relatively common condition that results from incomplete embryologic development?

Spina bifida is a developmental condition resulting from incomplete fusion of the vertebral arches within the lumbar region. Spina bifida occulta commonly presents asymptomatically with a tuft of hair and a small dimple in the overlying skin. More severe forms (spina bifida cystica) are categorized into three types: Spina bifida cystica with meningocele presents with protrusion of the meninges through the unfused vertebral arches. Spina bifida with meningomyelocele is characterized by protrusion both of the meninges and CNS tissues and is often associated with neurologic deficits. Rachischisis, also known as spina bifida cystica with myeloschisis, results from a failure of neural folds to fuse and is characterized by protrusion of the spinal cord or spinal nerves and meninges