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Spina bifida is one of the possible neural tube defects that can occur during early embryological development. There is a separate overview article that covers Neural Tube Defects.
In spina bifida, the vertebral arch of the spinal column is either incompletely formed or absent. The defect can occur anywhere from the base of the skull to the sacrum. It is most commonly found in the lumbar region. Neurological symptoms and signs generally correspond to the level of the defect. Spina bifida can be classified based on the type of spinal defect:
- Spina bifida occulta: The overlying skin is intact, there is a bony vertebral arch defect but no visible external overlying sac. There is no protrusion of the spinal cord or its membranes. This may affect up to 10% of the population and is most common at the lumbosacral junction. This is a closed form of spina bifida.
- Spina bifida cystica: There is both a vertebral defect and a visible cystic mass on the back. This is an 'open' form of spina bifida. It can be subdivided into:
- Meningocele - there is a cystic swelling of the dura and arachnoid mater which protrudes through the vertebral arch defect. No spinal neural tissue is present within the sac. There may be no neurological symptoms/signs.
- Myelomeningocele - spinal neural tissue forms part of the sac. Excluding spina bifida occulta, this is the most common form of spina bifida.
- Rachischisis - this is the most severe form of spina bifida cystica. The spine lies widely open and the neural plate has spread out on to the surface. It is often associated with anencephaly.
Arnold-Chiari type II malformation is often associated with myelomeningocele. Here there is cerebellar hypoplasia and displacement of the hindbrain through a widened foramen magnum. Cerebrospinal fluid (CSF) flow can be disrupted and hydrocephalus can result.
- The prevalence varies across time, by region and by both race and ethnicity. It also tends to be more common in girls.
- In 2008 in England and Wales, 32 notifications were made for children born with spina bifida. The rate was 1.3 per 10,000 births. The rate declined markedly after the policy of folic acid supplementation was introduced.
- Siblings of patients with spina bifida have an increased incidence of neural tube defects.
The cause of spina bifida is thought to be multifactorial:
- There appears to be a combination of genetic susceptibility with environmental precipitants, particularly shortage of folic acid in the mother's diet at a crucial stage in embryogenesis (days 17-30 when many mothers are unaware that they are pregnant). This is when the neural tube is forming and closing.
- Supplementation of newly pregnant mothers' diets and peri-conceptual advice to increase folic acid intake have been shown to reduce the incidence of neural tube defects significantly.
- There may also be abnormal folate metabolism in fetuses affected by neural tube defects.
- Chromosomal abnormalities including trisomy 13 (Patau's syndrome), 18 (Edwards' syndrome) and 21 (Down's syndrome) have been associated with neural tube defects.
- Association has been suggested with maternal diabetes and maternal alcohol exposure.
- Maternal use of sodium valproate and carbamazepine. Risk is greater with valproate.
Spina bifida cystica
- The abnormal herniation of the dural sac/neural tissue is usually evident, either during antenatal ultrasound scanning or at birth.
- Classically, the disruption of spinal cord function causes sensory dysfunction, flaccid paralysis and areflexia below the affected level. An alternative pattern includes the preservation of some distal reflex activity which is usually exaggerated.
- In cases of meningocele alone, the herniation of the meninges is often covered by skin so the lesion may be more difficult to detect.
- Imbalanced muscle forces can lead to spinal deformity, limb contractures and joint dislocations.
- Arnold-Chiari II malformation may present with stridor or apnoea. Impaired cerebellar function can affect balance, co-ordination and walking. Hydrocephalus, seizures and impaired cognitive function may be present.
Spina bifida occulta
- This is common and more difficult to detect.
- There is usually no long-term consequence or neurological sequelae.
- There may be no cutaneous marker, or there may be an obvious abnormality along the spine including:
- Asymmetry of the legs/feet may be present.
- Scoliosis or other spinal deformities may develop.
- Progressive neurological motor and/or sensory deficits can develop with associated bladder or bowel disturbance (because of associated tethering of the spinal cord).
- There may be low back pain as the individual gets older.
- A sudden onset of pain, motor and sensory loss and bladder dysfunction can occur after acute trauma if there is spinal cord tethering.
- The classical appearance of spina bifida cystica is not likely to be confused with other pathologies.
- Examine the spine and note the site and size of any lesion. Look for any spinal deformity.
- Perform a complete neurological examination of the newborn. Document any neurological abnormalities. This will act as a baseline.
- Measure head circumference.
- Assess cry and sucking reflex.
- Assess anal sphincter.
- Examine urinary stream.
- Perform a full motor examination, including assessment of muscle bulk, spontaneous active movements, muscle tone and movements in response to stimulation.
- Perform a full sensory examination.
- Look for foot and hip deformities.
- Raised levels of maternal serum alpha fetoprotein (AFP) at 16-18 weeks of gestation are found in neural tube defects.
- The 18-20-week fetal anomaly screening ultrasound scan allows detection and diagnosis of neural tube defects and is much more specific. Important prognostic information relates to the lesion level with a 'watershed' between L3 and L4.
- When amniocentesis is done, amniotic fluid AFP and acetylcholinesterase concentrations can be used to differentiate between open ventral wall defects (gastroschisis and omphalocele) and open neural tube defects.
Investigation of confirmed spina bifida
- Screening bloods can be carried out to detect any evidence of impairment of other organ systems, particularly renal impairment.
- Urine culture and urodynamics may be needed to detect any abnormality of the urinary tract caused by impaired bladder innervation.
- Latex allergy is relatively common among sufferers of spina bifida, probably due to inherent susceptibility and repeated exposure to surgical procedures. Enzyme-linked immunosorbent assay (ELISA) or skin-prick sensitivity testing may be needed to avoid illness caused by latex exposure. 40% of children with myelomeningocele may be latex-sensitive.
- Plain X-rays of the spine can help to detect any associated scoliosis and hip dysplasia or dislocation.
- CT and/or MRI scanning of the head and spinal cord may be conducted to look for evidence of the major complications of spina bifida, such as:
- Hydrocephalus due to Arnold-Chiari II malformation.
- Tethering of the spinal cord by fibrous bands.
- Gait analysis may be needed to evaluate a patient's functional mobility and allow intervention to improve independent mobility through the use of orthoses or surgery.
- Nurse any newborn with an open neural tube defect in the prone position and cover the defect with a sterile wet saline dressing.
- A multidisciplinary team approach is needed in the management of an infant with spina bifida.
- Treatment aims are to maximise mobility, prevent or ameliorate complications of spina bifida (particularly hydrocephalus), encourage as normal as possible development, and to help the individual maintain as independent a life as possible.
Repair of the defect
- Fetal surgery: management may start in the antenatal period through the use of fetal surgery. There is evidence that operating to repair myelomeningocele in fetuses that have had the condition detected by ultrasound scanning, before 25 weeks of gestation, with a lesion below the level of L2, reduces the incidence of the development of shunt-dependent hydrocephalus. The surgery is thought to improve CSF pressure dynamics and reduce the purportedly damaging effect of exposure of central nervous system tissue to amniotic fluid.
- There is little evidence currently that prenatal repair improves neurological function.
- In those patients who do not have prenatal surgery, there is a need to close and repair the spinal herniation and defect, and insert a ventricular shunting device if there is evidence of, or likelihood of, hydrocephalus.
- Those with Arnold-Chiari II malformation may need suboccipital craniotomy and decompression of the posterior fossa and tonsils if symptomatic.
- Ongoing management of mobility, utilising orthopaedic assessment, bracing and orthopaedic surgery, is often necessary. Spinal fusion, hip, pelvic or foot/ankle procedures are often needed. Prolonged physiotherapy, access to gym resources and/or adaptive training in children can be very helpful in maintaining independence and mobility.
- Developmental assessment by a paediatrician and help with maintaining a normal weight (weight gain is common due to impaired ambulation and can increase morbidity) are useful.
- Occupational therapy assessment and intervention can help to maximise function.
- Psychological input for the individual and their family to deal with the ramifications of their condition as they grow older is often needed.
- Neurosurgical follow-up is necessary to detect and treat complications such as hydrocephalus or a possible tethered cord.
- Bladder and bowel function can be maintained or aided by the use of a regular bowel voiding regimen and intermittent self-catheterisation.
- Meningitis (especially in open neural tube defects).
- Fractures (particularly of lower-limb long bones) and hip dislocations. These may be asymptomatic. There may be disuse osteoporosis and osteopenia.
- Pressure sores because of problems with mobility.
- Skin ulceration around orthoses/braces.
- Hydrocephalus due to Arnold-Chiari II malformation causing developmental impairment.
- Neurogenic bladder causing incontinence and urinary tract infection.
- Constipation due to impaired bowel innervation and anal sphincter function.
- Latex allergy leading to anaphylaxis.
With the advent of prenatal surgery, early repair of postnatal myelomeningocele, shunting to prevent hydrocephalus and expectant management of complications, most patients born with spina bifida survive into adulthood and develop relatively normally intellectually.
- Long-term survival depends on adherence to appropriate bowel and bladder regimens and careful management of urinary complications to prevent renal failure.
- In a UK-based survey looking at a cohort of patients born between 1963 and 1971 and surveyed around age 30 (26 to 33 years) found:
- 51% had died (largely the most severely disabled).
- 84% of survivors required CSF shunting (patients needing shunt revision had worse outcomes in terms of attainment and independence).
- 70% had an IQ >80.
- 37% lived independently in the community.
- 39% drove a car.
- 30% could walk >50 m.
- 26% were in open employment.
- One third needed daily care.
- A minority of patients either had need for respiratory support, were blind or were dialysis-dependent.
- Patients with hydrocephalus and a lesion at the level of L2 or above seem to be more dependent with regards to sphincter control, locomotion, self-care, social cognition, and communication.
- Half of deaths (after the age of 5 years) are sudden and unexpected. Most occur in the community and the most frequent causes are epilepsy, pulmonary embolus, acute hydrocephalus and acute renal sepsis.
- Peri-conceptual supplementation of folic acid and improved folate content in the diet of the general population (possibly through food fortification).
- Folic acid may also help to reduce the severity of neural tube defects as well as preventing their occurence.
- Improved prenatal diagnosis and prenatal surgery or termination of some pregnancies may reduce the future burden of disability caused by this condition.
Further reading & references
- Folic acid - an essential ingredient in making babies, Dept of Health; Current UK government policy on folic acid supplementation
- Foster MR; Spina Bifida, Medscape, Mar 2011
- Ellenbogen RG; Neural Tube Defects in the Neonatal Period, Medscape, Jan 2009
- Mitchell LE, Adzick NS, Melchionne J, et al; Spina bifida. Lancet. 2004 Nov 20-26;364(9448):1885-95.
- Congenital anomaly statistics 2008; Office for National Statistics
- Busby A, Abramsky L, Dolk H, et al; Preventing neural tube defects in Europe: population based study. BMJ. 2005 Mar 12;330(7491):574-5.
- Zlotogora J, Amitai Y, Leventhal A; Surveillance of neural tube defects in Israel: the effect of the recommendation for periconceptional folic acid. Isr Med Assoc J. 2006 Sep;8(9):601-4.
- Dunlevy LP, Chitty LS, Burren KA, et al; Abnormal folate metabolism in foetuses affected by neural tube defects. Brain. 2007 Apr;130(Pt 4):1043-9.
- Jallo GI; Neural Tube Defects, Medscape, Mar 2011
- Jentink J, Dolk H, Loane MA, et al; Intrauterine exposure to carbamazepine and specific congenital malformations: BMJ. 2010 Dec 2;341:c6581. doi: 10.1136/bmj.c6581.
- Cameron M, Moran P; Prenatal screening and diagnosis of neural tube defects. Prenat Diagn. 2009 Apr;29(4):402-11.
- Ausili E, Tabacco F, Focarelli B, et al; Prevalence of latex allergy in spina bifida: genetic and environmental risk Eur Rev Med Pharmacol Sci. 2007 May-Jun;11(3):149-53.
- Tulipan N, Sutton LN, Bruner JP, et al; The effect of intrauterine myelomeningocele repair on the incidence of shunt-dependent hydrocephalus. Pediatr Neurosurg. 2003 Jan;38(1):27-33.
- Hirose S, Farmer DL; Fetal surgery for myelomeningocele. Clin Perinatol. 2009 Jun;36(2):431-8, xi.
- Adzick NS, Walsh DS; Myelomeningocele: prenatal diagnosis, pathophysiology and management. Semin Pediatr Surg. 2003 Aug;12(3):168-74.
- Swaroop VT, Dias L; Orthopedic management of spina bifida. Part I: hip, knee, and rotational J Child Orthop. 2009 Oct 25.
- Oakeshott P, Hunt GM; Long-term outcome in open spina bifida. Br J Gen Pract. 2003 Aug;53(493):632-6.
- Verhoef M, Barf HA, Post MW, et al; Functional independence among young adults with spina bifida, in relation to hydrocephalus and level of lesion. Dev Med Child Neurol. 2006 Feb;48(2):114-9.
- Oakeshott P, Hunt GM, Poulton A, et al; Expectation of life and unexpected death in open spina bifida: a 40-year Dev Med Child Neurol. 2010 Aug;52(8):749-53. Epub 2009 Dec 9.
- Botto LD, Lisi A, Robert-Gnansia E, et al; International retrospective cohort study of neural tube defects in relation to folic acid recommendations: are the recommendations working? BMJ. 2005 Mar 12;330(7491):571. Epub 2005 Feb 18.
- De Wals P, Tairou F, Van Allen MI, et al; Spina bifida before and after folic acid fortification in Canada. Birth Defects Res A Clin Mol Teratol. 2008 Sep;82(9):622-6.
- Bol KA, Collins JS, Kirby RS; Survival of infants with neural tube defects in the presence of folic acid fortification. Pediatrics. 2006 Mar;117(3):803-13.
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Dr Sean Kavanagh, Dr Michelle Wright
Dr Hayley Willacy
Dr Helen Huins