Myelomeningocele (MM) is a developmental birth defect of the neural tube (NT), resulting in an open spinal cord lesion. The following are types of NT defects:
- Anencephaly occurs when the cephalic end of the NT fails to close, resulting in absence of a large portion of the brain, skull and scalp.
- Spina bifida occulta is a defect of the posterior bony elements of the spine only and is almost always asymptomatic.
- Meningocele is a protrusion of the meninges through the bony defect, without accompanying nervous tissue.
- MM is a spinal deformity involving the spinal cord, nerve roots, meninges, vertebrae and skin.
MM is a result of failure of the normal development of the neural tube, which typically starts on day 16 and is complete by day 28.
Epidemiology including risk factors and primary prevention
The birth prevalence of MM is 2:10,000 live births.1 Most cases of MM occur sporadically and are felt to have a multifactorial etiology. Maternal risk factors include folic acid deficiency, obesity, and diabetes. The role of folate in neural tube closure led to mandatory folate fortification of all cereal and bread products in the U.S. Exposure to hyperthermia and certain medications, such as valproic acid and carbamezapine, also increase the risk. The risk for recurrence in a family with MM is felt to be 3-5%.1 Whole genome sequencing suggests a role for de novo mutations in neural tube defects2 and genes that regulate folate metabolism have also been implicated.3
The most widely believed mechanism for MM is a failure of NT closure (i.e.neurulation). Normally, the mesoderm adjacent to the notochord forms muscle and bone around the neural tube to protect it. One theory suggests that an open caudal neural tube does not provide the necessary pressure in the cranial space to expand the cranial brain structures and may contribute to the development of the Chiari malformation.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time):
Although MM is a non- progressive disorder, secondary or associated conditions may clinically progressive over time.
- Hydrocephalus commonly presents in the neonate. Infants should be closely monitored by cranial imaging, serial head circumferences, developmental progress and for symptoms of increased intracranial pressure.
- Symptoms of brain stem dysfunction, related to an Arnold Chiari malformation, also often present in infancy.
- Neurogenic bladder is common and often presents at birth.
- Developmental delays are common. Careful screening and referral to the infant’s local early intervention program by 6 months of age is recommended.
- Ongoing surveillance for signs of hydrocephalus, shunt malfunction, brain stem dysfunction, tethered cord and syrinx should be routine.
- Vision and cognitive impairments may present at this time and screening is important prior to school entry.
Late childhood and adolescence
- Periods of rapid growth can be associated with progression of contractures in the lower extremities and increased risk for a tethered cord.
- It is not uncommon for patients with MM to have increasing difficulty with ambulation at this time, related to increasing weight and musculoskeletal deformities. Emphasis should be placed on maintaining physical activity, including opportunities for participation in social activities with peers.
- Risk for skin breakdown increases during adolescence. Close monitoring of nutrition and weight is important, due to the high risk for obesity.
- Sexuality should be discussed in a manner appropriate to the patient’s developmental abilities.
- Discussions about future vocational goals and transition to adult care should occur during adolescence.
- Obesity, metabolic syndrome, venous stasis and lymphedema are not uncommon.
- Bowel incontinence can be an important barrier to employment.
- Shoulder and wrist pain, including rotator cuff injuries are possible. The risk can be lessened with joint protection programs, appropriate wheelchair configuration, and teaching of proper propulsion patterns.5
- Individuals with MM are felt to be underemployed. Vocational counselors, the use of assistive technology and minimizing transportation barriers are recommended to increase employment.5
Specific secondary or associated conditions and complications
- Arnold Chiari II malformation (>90%), brainstem dysfunction
- Hydrocephalus (>90%), shunt malfunction
- Tethered cord or syrinx
- Variable cognitive deficits with greater difficulty with visual perceptual skills, executive functioning and attention and a relative strength in verbal skills.
- Neurogenic bowel and bladder
- Increased risk for a wide variety of musculoskeletal disorders, including scoliosis, hip dislocation, flexion contractures of the hips and knees, foot abnormalities, and rotational deformities.
- Variable sensory deficits and increased risk for pressure ulcers.
- Increased incidence of osteoporosis, associated with pathological fractures
- Increased incidence of obesity, short stature and precocious puberty
- Variable sexual dysfunction and fertility
- Increased incidence of depression
- High incidence of latex allergy
- Up to 10% of cases will have an associated chromosomal abnormality.
2. ESSENTIALS OF ASSESSMENT
- The majority of pregnancies, with isolated MM, will be uneventful.
- Signs of brain stem dysfunction, especially in an infant, include feeding difficulty, stridor, difficulty swallowing, aspiration pneumonia and apnea.
- Signs of shunt malfunction include headaches, cognitive changes, sedation and nausea/vomiting.
- Signs of a tethered cord or syrinx include changes in bowel or bladder function, new weakness or sensory deficits, pain, rapidly progressive scoliosis
- Bowel and bladder function should be addressed at every visit.
- Neurologic exam: fundoscopic exam, cranial nerves, mental status, sensation, strength, tone, reflexes and gait
- Musculoskeletal exam: spine, shoulders, hips, knees and feet.
- Serial head circumference in infants
- Skin integrity
- Evaluation of growth and nutrition
- Developmental screening including gross motor, fine motor, language and cognitive abilities.
- Independence with self-care skills
- Independence with mobility
- Evaluation of academic performance
- Evaluation of behavior, mood and social functioning
- Prenatal maternal serum α-fetoprotein between 16-18 weeks gestation suggests that an open NT disorder may be present, which can be confirmed with ultrasound and amniocentesis.
- Routine measurement of creatinine and blood urea nitrogen to evaluate kidney function.
- Urinalysis and urine culture when symptoms of a urinary tract infection are present.
- Prenatal ultrasound can detect the characteristic “lemon and banana” signs related to the shape of the head and the herniation of the cerebellar vermis.
- Magnetic resonance imaging of the spine to evaluate for brainstem compression, syrinx or tethered cord.
- Brain computed tomography to evaluate hydrocephalus.
- Plain films to evaluate musculoskeletal disorders, including scoliosis.
- Renal ultrasonography to rule out hydronephrosis or other renal anomalies.
- Voiding cystourethrography to evaluate for reflux and to help to determine if antibiotic prophylaxis is needed.
- Dual-energy x-ray absorptiometry (DEXA) scan in the setting of pathological fractures.
Supplemental assessment tools
- Urodynamics to evaluate bladder function.
- The International Myelodysplasia Study Group Criteria for Assigning Motor Levels provides a standard means of assigning motor levels.6
- Neuropsychological testing
- Modified Ashworth Scale
- Vision and hearing screens
Early prediction of outcomes
Muscle strength is strongly associated with ambulatory outcome.
- Grade 0-3/5 iliopsoas strength is associated with partial or complete reliance on wheelchair mobility
- Grade 4-5/5 iliopsoas strength is associated with community ambulation in the majority of patients
- Grade 4-5/5 gluteal and anterior tibialis function is associated with community ambulation, without aids or braces7
Social role and social support system
Families who have a child with MM are at risk for significant psychological and financial stress and sociodemographic attributes, such as being uninsured, are associated with worse SB outcomes.8 Children with MM require a tremendous amount of care and appropriate child care can be difficult to find, given the complex medical needs of some children. Families are also faced with frequent medical appointments, unexpected illnesses, and the potential need to make costly home modifications.
Until the mid 1980’s, many medical centers selected infants born with MM for ongoing medical support and treatment based on published prognostic criteria. In 1985, a law was passed on the basis of a baby girl with MM whose parents declined surgery for hydrocephalus, which mandates provision of life-sustaining medical treatment to most seriously ill infants.9 Similar issues still present themselves when families are considering early termination of pregnancy based on prenatal screening and the option of prenatal repair of MM.
3. REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
A widely established, research-based guideline for MM does not exist. The Spina Bifida Association published the third edition of Guidelines for Spina Bifida Health Care Services throughout the Lifespan in 2006, but the guidelines were generally not widely followed.10
At different neurologic levels
The rehabilitation plan will vary based on the level of the lesion, the developmental age of the child, family resources and individual comorbidities such as cognitive impairment. Evaluation of function and promotion of independence should be a primary focus for all patients.
- Kyphoscoliosis is extremely common. Early management includes supportive seating and consideration of thoracolumbosacral orthosis (TLSO). Orthopedic surgery should be considered.
- Functional ambulation is rare and wheelchair mobility should be advocated for very early.
- Dynamic or static standers should be encouraged by the age of 12-18 months. Consideration can be given to the use of Reciprocating Gait Orthoses or HKAFOs in early school age children. It is very unusual for children to continue to use these gait aides into adolescence.
- Hip and knee flexion contractures are common.
- Hip dislocations are common, but typically not a contraindication to walking.
- Ground reaction AFOs are typically needed to avoid the crouched gait caused by lack of plantarflexion strength.
- KAFOs are also sometimes useful, especially to limit excessive valgus or varus knee motion.
- Adaptive gait aids, such as a reverse walker for young children and loftstrand crutches in slightly older children, can be very helpful.
- Wheelchair use should be considered early to facilitate independent community mobility.
- Hip and knee flexion contractures remain common, but hip dislocation is less likely.
- If the tibialis anterior is unopposed, a calcaneus foot is likely. Excessive pronation is also common, especially in weight bearing.
- Ground reactive AFOs are typically needed to avoid the crouched gait caused by plantarflexion strength.
- Many children will benefit from adaptive gait aids, especially when they are learning to walk and as they get taller and heavier.
- Wheelchair use remains common in the community, especially in older children.
- Children can often learn to walk well without any adaptive aids or braces.
- Distal weakness can lead to significant foot deformities including pes cavus, which may benefit from orthotics.
Coordination of care
The multidisciplinary clinic remains the model for health care delivery to children with MM.
Patient & family education
Caregivers of children with MM will require extensive education related to the complex nature of their medical needs. Family support, including financial counseling, options for respite care, referrals to support and advocacy groups should be offered. Children with MM often have limited social interactions with their peers. Referrals to community resources for recreational activities and adaptive supports should be offered. As the child grows older, it is important to shift the focus to educating the child in a manner that is appropriate to their developmental or cognitive abilities. Adolescent patients should be encouraged to take increasing responsibility for their own care and advocacy.
Measurement of Patient Outcomes
In 2008 the Centers for Disease Control and Prevention, in partnership with the Spina Bifida Association, launched the National Spina Bifida Registry. This created a funded computerized reporting and database system that is being used to evaluate important clinical questions using anonymous patient data.11
4. CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
Cutting edge concepts and practice
A randomized trial (Myelomeningocele Study MOMS) of prenatal versus postnatal repair of MM revealed a reduced need for shunting and improved motor outcomes at 30 months in the prenatal repair cohort, but was associated with maternal and fetal risks.12 This landmark study has resulted in a number of centers offering prenatal repair, but variation in practice patterns for offering and performing this maternal–fetal surgery exists among centers. (13)
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
Gaps in the evidence-based knowledge
Many gaps in evidence-based knowledge have been identified including: the optimal treatment of hydrocephalus, indication for tethered cord release, optimal management of hip dislocation, management of osteoporosis, optimal pressure sore prevention and treatment, instructional and developmental interventions that facilitate learning, optimal orthotic use, and how to effectively promote self-care.9
- Au KS, Ashley-Koch A, Northrup H. Epidemiology and genetic aspects of spina bifida and other neural tube defects. Dev Disab Res Rev. 2010;16:6-15.
- Lemay P, Guyot MC, Tremblay E, et al. Loss-of-function de novo mutations play an important role in severe human neural tube defects. J Med Genet. 2015; 52(7): 493-7.
- Copp AJ, Stanier , Greene ND. Neural tube defects – recent advances, unsolved questions and controversies. Lancet Neurology. 2013; 12(8): 799-810.
- Clayton DB, Brock JW, Joseph DB. Urologic management of spina bifida. Dev Disab Res Rev. 2010;16:88-95.
- Dicianno BE, Kurowski BG, Yang JMJ et al. Rehabilitation and medical management of the adult with spina bifida. Am J Phys Med Rehabil. 2008; 87:1027-50.
- Hurtleff DB. IMSG. International Myelodysplasia Study Group Database Coordination. Seattle WA, USA: Department of Pediatrics, University of Washington, 1993.
- McDonald CM, Jaffe KM, Mosca VS et al. Ambulatory outcome of children with myelomeningocele: effect of lower-extremity muscle strength. Dev Med child Neurol. 1991;33(6):471-2.
- Schechter MS, Tiebin L, Minn S, et al. Sociodemographic attributes and spina bifida outcomes. Pediatrics 2015; 135(4):e957-64.
- Sandler AD Children with spina bifida: key clinical issues. Pediatr Clin N Am 2010;57;879-92.
- Liptak GS, Samra AE. Optimizing health care for children with spina bifida. Dev Disab Res Rev. 2010;16;66-75.
- www.cdc.gov/ncbddd/spinabifida/NSBPRregistry.html Accessed November 4, 2016.
- Adzick NS, Thom EA, Spong CY, et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele. N Engl J Med 2011;364:993-1004.
- Moise KJ, Moldenhauer JS, Bennett KA, et al. Current selection criteria and perioperative therapy used for fetal myelomeningocele surgery. Obstetrics and Gynecology. 2016; 127(3): 593-7.
Original Version of the Topic
Mary McMahon, MD. Myelomeningocele (Spina Bifida). 05/12/2013.
Mary McMahon, MD
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Ashlee Bolger, MD
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