Spina bifida overview

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Overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:  Syed Musadiq Ali M.B.B.S.[2], Mohamadmostafa Jahansouz M.D.[3]

## Overview

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## Historical Perspective

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Spina bifida has existed as long as the history of humanity. Evidence of children with characteristic features of spina bifida has been found in the archeological findings and a large number of anthropological figures from early civilizations. Spina bifida was first discovered by Hippocrates, (born c. 460 bce, island of Cos, Greece—died c. 375 bce, Larissa, Thessaly). The first definitive description of spina bifida was made by the Dutch clinician Pieter van Foreest (1522–1597) in the late 1500s. In 1614, Nicolaas Tulp (whose real name was Claes Piereszoon) was the first who coined the term spina bifida. Ligation or amputation of the dural sac was the surgical treatment of spina bifida for centuries. The outcome of this procedure was almost always fatal because of central spinal fluid leakage and infection or the secondary progressive untreated hydrocephalus. In 1918, Charles H. Frazier started better surgical concepts of repair of spina bifida, with multilayer closures using dura, fascia, muscles, and skin advocated. In 1967, a study by Sharrard, confirmed that better results were obtained by performing the surgery of spina bifida in the perinatal period. Now, the surgery of spina bifida in the perinatal period, is the preferred treatment.

## Classification

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Spina bifida may be classified according to the level of the lesion into 3 subtypes: Thoracic, lumbarand sacral. It also may be classified according to the tyoe of the vertebrate defect into 2 subtypes: Spina bifida occulta and spina ifida aperta. Meningocele is a protrusion of the meninges, unaccompanied by neural tissue, through a bony defect in the vertebral column. Myelomeningocele is the most severe form of spina bifida. It happens when both the meninges and the bottom end of the spinal cord push through the hole in the spine, forming a large fluid-filled sac that bulges out of a patients back.

## Pathophysiology

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Spina bifida is a congenital malformation in which the spinal column is split (bifid) as a result of failed closure of the embryonic neural tube, during the fourth week post-fertilization. In normal infants, the neural tube closes by the end of the 4 week of conception, but in patients with spina bifida, some parts of the neural tube fails to develop or close that causes defects in the spinal cord and in the vertebral bones. Spina bifida also may be classified according to the tyoe of the vertebrate defect into 2 subtypes: Spina bifida occulta: In this type of spina bifida, the defect of vertebrate is covered by skin ("Occulta" means "hidden"). The spinal cord does not stick out through the skin, although the skin over the lower spine may have a patch of hair, a birthmark, or a dimple above the groove between the buttocks. Spina ifida aperta: In this type of spina bifida , the defect is widely open and is sub classified into 2 types: Meningocele and Myelomeningocele. Spina bifida may be caused by the increase of cerebrospinal fluid (CSF) volume in the central nervous system during the first weeks of embryogenesis. Venous insufficiency is the main cause of the increase of cerebrospinal fluid and it may be caused by any disease that reduces space for venous volume. The development of spina bifida may be the result of multiple genetically defect in the genes important in the metabolism of: Folic acid, glucose, retinoids, apoptosis, genes that regulate transcription in early embryogenesis, methionine Cycle genes, methylation genes, glucose Homeostasis genes, cell Recognition and Migration genes, DNA Repair genes and transcription Factors genes. Conditions associated with spina bifida include: Hydrocephalus, chiari II Malformation, paralysis, urination and deification incontinences, atex Allergy, learning Disabilities, sexual problems, emotional problems, obesity and vision problems.

## Causes

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There is no well known cause of spina bifida. It may result from a variety of occupational, environmental, genetic, and viral risk factors, such as a family history of neural tube defects and folate deficiency.

## Differentiating spina bifida from Other Diseases

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Spina bifida must be differentiated from other diseases that causes vertebral column defects, spinal deformity and neurologic abnormalities or gait abnormalities, such as: Terminal myelocystocele, spine segmental dysgenesis, Caudal regression syndrome (sacral agenesis), multiple vertebral segmentation disorder, VACTERL association, arnold-chiari malformation, syringomyelia, Scoliosis, and leg length discrepancy.

## Epidemiology and Demographics

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The incidence of spina bifida is approximately 3.5 per 10,000 live births per year in the U.S. The prevalence of spina bifida is approximately 187 to 890 per 100,000 live births. Before 1960, the case-mortality rate of all forms of spina bifida was 90% to 88%. Now the mortality rate is approximately is 10.1%. The overall ventriculoperitoneal shunt requirement rate is 33.8%. The paraplegia rate is 30.7%. The neurogenic bladder rate is 51.6%. The infection rate is 6.4% after the surgical procedure. Spina bifida is more commonly observed among preterm newborns. Spina bifida usually affects individuals of the Malays and Chinese and Indians race. Female are more commonly affected by than male. The male\male+female ratio is approximately 42%.

## Risk Factors

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Risk factors in the development of spina bifida may be occupational, environmental, genetic, and viral. Common maternal nutrition risk factors in the development of spina bifida include: Alcohol use, caffeine use, low folate intake, low dietary quality, elevated glycaemic load or index, low methionine intake, low serum choline level, low serum vitamin B12 level, low vitamin C level, low zinc intake, smoking, hyperthermia, low socio-economic status, maternal infections and illnesses, pregestational insulin-dependent diabetes, pregestational obesity, psychosocial stress and valproic acid use. Environmental factors in the development of spina bifida include: Ambient air pollution, disinfectant by-products in drinking water, indoor air pollution, nitrate-related compounds, organic solvents, pesticides and polycyclic aromatic hydrocarbons.

## Screening

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First time in 1975, it was reported that AFP levels are often raised in maternal blood in association with neural tube defect of the fetus and it is an important advance in obstetric practice since it presents the possibility of a screening programme leading to early diagnosis and termination of these abnormal pregnancies. Screening for spina bifida by mother's blood's AFP [alpha‐fetoprotein] is recommended for all pregnant women with Triple Test. Triple test looks for three specific substances: AFP, hCG, and Estriol. Triple test is performed between the 15th and 20th week of pregnancy preferably in the 16th -18th week. All pregnant women should have triple test dureng pregnancy, but is is more important in pregnants with: Family history of birth defects, age of 35 years or older, Diabetes and use insulin, viral infection during pregnancy andexposure to high levels of radiation. In patients with high level of AFP, use of ultrasound and amniocentesis may be useful to diagnose open neural tube defects including spina bifida.

## Natural History, Complications, and Prognosis

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Prognosis of patients with spina bifida is generally poor. Early clinical features of spina bifida include: Weakness or paralysis in the legs, Urinary incontinence, Bowel incontinence, Sensation problems in the lower extremity, Motor problems in the lower extrimity and Hydrocephalus. If left untreated, 50% of patients with congenital anomalies, especially spina bifida may die soon after birth in the underdeveloped countries. Renal failure is the commonest cause of death in patients with spina bifida. Common complications of [disease name] include: Cardiac disease, Respiratory disease, Suicidality and Cancer.

## Diagnosis

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### Diagnostic Study of Choice

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Ultrasound is the imaging modality of choice for characterisation of the open spina bifida spinal lesions. On two and tree-dimensional ultrasound, spina bifida is characterized by: Vertebral defect, splayed vertebral pedicles and disrupted vertebrae. The ultrasound must be performed when a positive alpha-fetoprotein is detected in the triple screening test between the 15th and 20th week of pregnancy to confirm the diagnosis.

### History and Symptoms

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Early symptoms of patients with spina bifida include: Weakness or paralysis in the legs, Urinary incontinence, Bowel incontinence, Sensation problems in the lower extremity, Motor problems in the lower extrimity, Headache, orthopedic abnormalities, difficulties with executive functions, academic skills problems, learning disability and allergy to latex.

### Physical Examination

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Most patients with spina bifida have normal vital signs. Skin examination of patients with spina bifida is usually remarkable for: Spinal area discoloration or birthmarks, protrusions in the lumbar spine, dimples in the lumbar spine and patch along the spine. HEENT examination of patients with spina bifida is usually remarkable for: Enlarging head, bulging fontanelle, enlarged scalp veins, Cranial bones suture diastasis and positive Macewen sign. Cardiovascular examination of patients with spina bifida is usually normal but congenital anomalies of the spine have been associated with malformations of the cardiovascular systems. Congenital anomalies of the spine also may be associated with malformations of the genitourinary system. Neuromuscular examination of patients with spina bifida may be remarkable for: Paralysis, sensation problems, Scoliosis, pressure ulcers, learning disabilities, Clonus, Hyperreflexia or hyporeflexia, positive (abnormal) Babinski unilaterally, muscle rigidity, muscle weakness unilaterally or bilaterally, abnormal gait and Dysmetria.

### Laboratory Findings

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There are no specific laboratory findings in the newborn associated with spina bifida. An elevated concentration of Maternal Serum Alpha-Fetoprotein may be predictive for contemporary detection of spina bifida. Screening for spina bifida by mother's blood's AFP [alpha‐fetoprotein] is recommended for all pregnant women with Triple Test. Triple test looks for three specific substances: AFP, hCG, and Estriol. Triple test is performed between the 15th and 20th week of pregnancy preferably in the 16th -18th week.

### Electroencephalogram

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Single Infantile electroencephalogram (EEG) recordings have limited prognostic value for infants born with spina bifida. Serial EEG recordings in combination with other clinical or neurophysiological investigations might ameliorate the contributing predictive value of neonatal EEG.

### X-ray

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Spina bifida occulta is found in up to 10% of people and usually occurs in the low spinal region and in most cases it is asymptomatic. An x-ray may be helpful in the diagnosis of cases of spina bifida who have not been diagnosed before. Findings on an x-ray suggestive of of spina bifida include: Failure of closure of the vertebral arch and scoliosis.

### Echocardiography and Ultrasound

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Compared with the general population, the prevalence of congenital heart disease in newborns with myelomeningocele is increased , however critical disease is uncommon. When the myelomeningocele is prenatally diagnosed, antenatal cardiac screening is complete and normal, and the newborn is clinically well, preoperative echocardiography is unnecessary. Ultrasound is the imaging modality of choice for characterisation of the open spina bifida spinal lesions. On two and tree-dimensional ultrasound, spina bifida is characterized by: Vertebral defect, splayed vertebral pedicles and disrupted vertebrae. The ultrasound must be performed when a positive alpha-fetoprotein is detected in the triple screening test between the 15th and 20th week of pregnancy to confirm the diagnosis.

### CT scan

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CT scan is not widely used for diagnosis of spina bifida but, it may be helpful in the diagnosis of hydrocephalus and during childhood, a patient with spina bifida will have multiple CT scans of the head.

### MRI

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Spinal and brain MRI may be helpful in the diagnosis of spina bifida. Findings on MRI diagnostic of spina bifida include:Herniation of a CSF filled sac through spina bifida, CSF attenuation lesion in conus medullaris and other parts of the CNS and short and thick filum terminale.

## Treatment

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### Medical Therapy

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Spina bifida requires prompt treatment. The mainstay of treatment for spina bifida is surgery.

### Surgery

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The management of open spina bifida is surgery within 48 h of birth. The defect in the spine is closed to minimize the risk of ascending infection that can result in meningitis. Prenatal surgery is the preferred treatment for spina bifida and it usually is done before the 26th week of pregnancy and it may prevent continuing damage and improve clinical outcome. Intrauterine repair of spina bifida confers multiple advantages to infants, including: Lower rates of shunt dependency, lower rates of hindbrain herniation and better motor and disability functional outcomes. Surgery after birth is done in patients who did not underwent prenatal surgery but the prognosis is worse and there are more possible complications after surgery in comparison with the prenatal surgery. The management of open spina bifida is surgery within 48 h of birth. The defect in the spine is closed to minimize the risk of ascending infection that can result in meningitis. Prenatal surgery is the preferred treatment for spina bifida and it usually is done before the 26th week of pregnancy and it may prevent continuing damage and improve clinical outcome. Intrauterine repair of spina bifida confers multiple advantages to infants, including: Lower rates of shunt dependency, lower rates of hindbrain herniation and better motor and disability functional outcomes. Surgery after birth is done in patients who did not underwent prenatal surgery but the prognosis is worse and there are more possible complications after surgery in comparison with the prenatal surgery.

### Primary Prevention

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A protective effect of folate against the development of neural tube defects (NTDs), specifically, spina bifida, is now well recognized, having been established by a lot of clinical research studies over the past half-century. Effective measures for the primary prevention of spina bifida include: Not drinking alcohol, not smoking, not taking drugs, taking Folic Acid and taking oral daily folate for all pregnant women. Neural tube closure is completed 28 days (four weeks) from conception, and the preventive effect of folic acid is not effective after that period. So, folate supplementation should start at least 4 weeks before conception and it should continue until at least two months after conception. The recommended intakes of folate are 4 mg/d for those at high-risk pregnancies(by virtue of a previous NTD pregnancy outcome) and 0.4 mg/d for all others.

## References

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