When the spinal column does not fuse together, allowing outward growth of the spinal contents, including cerebral spinal fluid (CSF), spinal cord, nerves lined with meninges, and sometimes skin (Fig. 5.2), this defect in the spine is called a myelomeningocele, and the disease process is spina bifida (Fig. 5.3). The defect can occur anywhere in the spinal axis, with 85 % in the lumbosacral spine, 10 % in the thoracic spine, and 5 % in the cervical spine (Cohen and Robinson 2001).

The prognosis of a myelomeningocele is highly dependent on the size and location of the spinal defect and on the severity of its comorbidities, which include hydrocephalus and Chiari II malformation. The most common clinical complications are paralysis, hydrocephalus, and bowel and bladder incontinence. The survival rate of spina bifida has increased with advanced and more aggressive surgical intervention. Historically, dating back to the 1960s, infants born with spina bifida were managed conservatively without surgery. Many infants died from perinatal problems, hydrocephalus, or infection. A study by Laurence in South Wales evaluated children born between 1956 and 1962 that were not surgically treated and found that only 11 % of the children survived to 10–16 years of age (Laurence 1974). Although this is a high rate of mortality demonstrating the natural progression of untreated MM, the percentage of survival gave thought to more aggressive treatment. Throughout the 1960s, continued research showed a substantially higher rate of survival for infants who had immediate surgical repair of the MM and surgical treatment of hydrocephalus (Park 1999). Ames and Shut (1972) evaluated 171 patients with myelomeningocele that were treated surgically between 1963 and 1968. They found the survival rate continued to improve, climbing to 50–80 % for children 3–8 years old (Ames and Shut 1972).

Later, in the 1970s and 1980s, the trend for aggressive and immediate surgical intervention continued and became the current standard of care. Throughout the 1990s, researchers learned more about the untoward effects of hindbrain herniation and hydrocephalus to the fetus and the overall impact on lifetime livelihood. Currently, there is the “two-hit” pathogenesis theory of MM. Not only is the incomplete neural tube the cause, but also the exposed part of the cord is further injured during gestation by exposure to amniotic fluid, direct trauma, and hydrodynamic pressure, especially in the third trimester. This theory brought about the idea of fetal MM surgery (Adzick 2010; Meuli and Moehrien 2014). If the defect can be repaired prenatally, the spinal cord will be protected during remaining gestation and labor. To determine whether early fetal surgery would be a greater benefit than risk, a landmark 7-year National Institutes of Health-funded trial called the Management of Myelomeningocele Study (MOMS) was conducted from 2003 to 2010. The outcome of this study continues to mold and shape the care of these patients. Results of the MOMS two study are due out in November, 2016, which will further guide the direction of care for patients with myelomeningocele.

Today, we understand that although these infants are often born with significant neurological deficits, many have normal intelligence and the capability to enjoy a productive and fulfilling life. Major factors that affect long-term clinical outcomes are intelligence quotient (IQ), ambulatory function, degree of bowel and bladder function, the presence of hydrocephalus, or symptomatic Chiari II malformation, and upward to 20 % may have seizures in childhood (Liptak 1997). Intellectual ability is strongly influenced by the presence and severity of hydrocephalus, the level of the defect and associated handicap, and a history of having central nervous system infection (e.g., meningitis). Individuals with myelomeningocele may have below-average cognitive abilities or mild intellectual disability. It is understood that a lower level lesion may correlate with less motor deficit and higher intellectual capability. The ability to ambulate is directly correlated to the anatomic level of the spinal defect and subsequent neurological deficit. Children with a lower spinal defect have a greater chance of ambulating. Approximately 95 % of children with lower lumbar or sacral level defects can achieve walking, with or without assistive devices (Sakakibara et al. 2003). The ability to ambulate ranges from independent walking, or requiring assistive mobility devices (orthotic braces, crutches, or walker), to complete dependence on a wheelchair (Fig. 5.4e). Bowel and bladder dysfunction is a notable determinant of social acceptance. Some patients may be incontinent of bowel and bladder, while others can achieve “social continence.”

Prenatal screening is helpful in the detection of an open neural tube defect and is extremely important in planning a timely and safe delivery. Screening and a consequent diagnosis can be determined with a maternal serum alpha-fetoprotein (MSAFP), ultrasound, or amniocentesis (Coniglio et al. 1997). The MSAFP is done between 14 and 21 weeks and is optimal between 16 and 18 weeks of gestation. If this number is higher than the normal value range, it may be an indicator of a possible neural tube defect. This is a screening test, and a normal AFP does not completely exclude the possibility of a myelomeningocele. An ultrasound is done between 15 weeks and up to the end of pregnancy for the assessment of the fetal age and general anatomy of the brain and spine (d’Ercole et al. 2003). If a neural tube defect is found, the patient is referred to a perinatologist for a high-resolution ultrasound and possible amniocentesis. Some medical facilities have the capability to do a prenatal ultrafast MRI of the mother’s abdomen for structural assessment of the fetus and the severity of hydrocephalus (Fig. 5.5). Fetal blood sampling and chorionic villi sampling are not useful in the determination of an open neural tube defects.