A meningomyelocele (also called myelomeningocele or spina bifida) is a herniation of the meninges and spinal cord through a spinal defect. It is a form of open spinal dysraphism resulting from a neural tube defect (NTD) involving failed closure of the neural tube. Embryologically, failure of primary neurulation most often occurs in the posterior neuropore, resulting in lumbosacral region defects. The etiology is multifactorial, and reduced folic acid is associated with the condition. Despite recommendations for folic acid fortification and supplementation, the incidence of meningomyelocele is 3.4 per 10 000 live births in the United States. Marked increases of meningomyelocele and spina bifida have been seen in Ethiopia due to lack of folic acid.

Diagnosis is often made in utero. The defect is visible on examination, and disruption of the sac can result in drainage of cerebrospinal fluid (CSF). Positional deformities of the feet, legs, and hips are common. Weakness and sensory loss below the level of the meningomyelocele may be partial or complete. Bowel and bladder involvement are common.

There is a high association with Chiari II malformations. Hydrocephalus can occur and may be present at birth or manifest later in the newborn period.

This NTD warrants early surgical closure. Survival rates are good with surgical repair, but patients often require long-term care and follow-up with multidisciplinary teams.

Related topic: spina bifida