1902
Spina bifida refers to a birth defect in which there is incomplete closing of the spine and the membranes around the spinal cord during early development in pregnancy.
Failure of the neurotube to fuse doing the third week of gestation leads to an open neural – tube defect at the cranial level (anencephaly) , the spinal level (myelomeningocele) or both (craniorachischisis).
There is an estimated 166,000 persons in the US living with spina bifida as adults.
Anencephaly and craniotachischiasid are lethal during gestation to soon after birth.
Spina bifida is believed to be caused by a combination of genetic and environmental factors: maternal diabetes, hyperthermia, anti-convulsant agents, obesity, and toxins, contributed to by multiple genomic sequence variations.
Results from the non closure of the neural tube at the spinal cord levels and children may survive with life long problems of paralysis, bowel and bladder incontinence along with other physical handicaps.
Prevalence of spina bifida in North America and most upper middle income and high income countries is approximately 34 to 37 cases per 100,000 live births.
In regions where folate is not fortified in food the prevalence is 54 to 87 cases per hundred thousand live births, and as high as 300 per hundred thousand in low income areas.
30% of cases occur despite folate supplementation.
Spina bifida is a type of neural tube defect related to but distinct from other types such as anencephaly and encephalocele.
Spina bifida occurs when local regions of the neural tube fail to fuse or there is failure in formation of the vertebral neural arches.
Most common of congenital anomalies of the CNS that are compatible with life.
The neurologic presentation of a newborn with SB depends on the spinal level of the defect, with infants with a low sacral myelomeningocele may have normal findings on neurologic exam, whereas infants with higher lesions in the lumbar or thoracic region may present with neurogenic bladder and lower extremity center sensorymotor defects ranging from foot weakness to paraplegic.
After birth CT or MRI imaging of the head is performed to rule out hydrocephalus:other organ congenital anomalies need to be ruled out in a comprehensive care plan for neonates and infants.
Other organs, such as the heart, bladder, and extremities involving the foot, leg, or hip deformities need to be evaluated.
There are three main types: spina bifida occulta, meningocele and myelomeningocele.
Meningocele and myelomeningocele are grouped as spina bifida cystica.
It is most commonly located in the lower back, but in rare cases it may be in the middle back or neck.
At its most common and most severe form, myelomeningocele the spinal cord and menigeal covering are exposed dorsally, as a cystic defect associated with a vertebral arch deformity.
It is likely the result of a two-hit process, initiated by failure of primary neurulation and followed by progressive neurodegeneration due to amniotic fluid toxicity and trauma during gestation.
Spina bifida occulta has no or only mild signs.
Spina bifida occulta findings may include a hairy patch, dimple, dark spot or swelling on the back at the site of the gap in the spine.
Meningocele typically causes mild problems.
Meningocele presents with a sac of fluid present at the gap in the spine.
Myelomeningocele, also known as open spina bifida, is the most severe form of spina bifida.
A myelomeningocele is an open defect consisting of a malformed spinal cord that has no dura, bone, muscle, or skin coverage and has an associate accessibility susceptibility to infection and CSF leakage.
Myelomeningocele is associated with poor ability to walk, impaired bladder or bowel control, hydrocephalus, a tethered spinal cord and latex allergy.
Findings:Hairy patch, dimple, dark spot, swelling on the lower back.
Causes: Spina bifida is believed to be due to a combination of genetic and environmental factors.
Mortality is around 20% by age 5.
With the recommendation to consume folate in pregnancy the incidence of neural tube defects has decreased, but has been stabilized since 2003.
Folate delivered to the mother has reduced both he first occurrence of fetal open neural tube defects in women who had never had an affected pregnancy, and the subsequent occurrence of fetal open neural tube defect in women who have previously had an affected pregnancy by at least 70%.
Prevalence about 1.9 per 10,000 live births.
Most frequent form is myelomeningocoel.
Incidence of myelomeningocoel stable at 3.4 per 10,000 live births.
Myelomeningocoel has an extrusion of the spinal cord into a sac filled with CSF.
10% death rate in liveborn infants with myelomeningocoel.
Damage to spinal cord and peripheral nerves is not reversible.
Damage to spinal cord and peripheral nerves usually evident at birth.
Risk factors:
Not having enough folate in the diet before and during pregnancy also plays a significant role.
Other risk factors include certain antiseizure medications, obesity and poorly controlled diabetes.
After having one child with the condition, or if one of the parents has the condition, there is a 4% chance that the next child will also be affected.
If a blood test or amniocentesis finds a high level of alpha-fetoprotein (AFP), there is a higher risk of spina bifida.
Ultrasound examination may also detect spina bifida.
Medical imaging can confirm the diagnosis after birth.
Adding folic acid to flour has been found to be effective preventative.
Open spina bifida can be surgically closed before or after birth.
A shunt may be needed in those with hydrocephalus.
Crutches or wheelchairs may be useful.
Urinary catheterization may also be needed.
A tethered spinal cord may need surgery.
The frequency of spinal bifida is 0.1–5 per 1000 births.
On average, in developed countries, including the United States, it occurs in about 0.4 per 1,000 births.
In India, it affects about 1.9 per 1,000 births.
In Europeans there is a higher risk compared to Africans.
Spina bifida occulta is the mildest form of spina bifida.
In spina bifida occulta, the outer part of some of the vertebrae is not completely closed, so the spinal cord does not protrude.
The skin at the site of the lesion may be normal, or it may have some hair growing from it; there may be a dimple in the skin, or a birthmark.
Spina bifida occulta is not associated with increased AFP, as the dural lining is maintained.
In many the diagnosis is unknown, as the condition is asymptomatic in most cases.
Spina bifida occulta and back pain are not correlated, although one study suggested patients with back pain, the severity was worse if spina bifida occulta is present.
Posterior meningocele is the least common form of spina bifida.
A single developmental defect allows the meninges to herniate between the vertebrae, but the nervous system remains undamaged.
Individuals with meningocele are unlikely to have long-term health problems, although cases of tethered cord have been reported.
Causes of meningocele include teratoma and other tumors of the sacrococcyx and of the presacral space.
A meningocele may also form through dehiscences in the base of the skull, and may be classified by their localization as occipital, frontoethmoidal or nasal.
An endonasal meningocele lies at the roof of the nasal cavity and is treated surgically.
Encephalomeningoceles contain brain tissue.
Myelomeningocele (MMC), also known as meningomyelocele, is a type of spina bifida that often results in the most severe complications and affects the meninges and nerves.
With myelomeningocele, the unfused portion of the spinal column allows the spinal cord to protrude through an opening.
Myelomeningocele occurs in the third week of embryonic development.
It occurs, due to a failure of neural tube complete pore closure.
With myelomeningocele the meningeal membranes that cover the spinal cord also protrude through the opening, forming a sac enclosing the spinal elements: meninges, cerebrospinal fluid, and parts of the spinal cord and nerve roots.
Myelomeningocele is also associated with Arnold–Chiari malformation.
Toxins and conditions associated with MMC formation include: calcium-channel blockers, carbamazepine, hyperthermia, and valproic acid.
Spina bifida with myelocele is the most severe form of myelomeningocele.
It involves an area of flattened, plate-like mass of nervous tissue with no overlying membrane.
Such exposure of these nerves and tissues make the baby more prone to life-threatening infections, such as meningitis.
The spinal cord and the nerves that originate at that level of the cord and protrude are damaged, or not properly developed, and there is
usually some degree of paralysis and loss of sensation below the level of the spinal cord defect.
The more cranial the level of the defect, the more severe the associated nerve dysfunction and resultant paralysis that may occur.
Accompanying symptoms may include ambulatory difficulties , loss of sensation, deformities of the hips, knees or feet, and loss of muscle tone, leg weakness and paralysis.
Orthopedic abnormalities of club foot, hip dislocation, scoliosis may be present, as may bladder and bowel control problems, including incontinence, urinary tract infections, and poor kidney function, pressure sores, skin irritations, and abnormal eye movements.
68% of children with spina bifida have an allergy to latex.
The spinal cord lesion or the scarring due to surgery may result in a tethered spinal cord or scarring of the spinal cord can cause significant traction and stress on the spinal cord and can lead to a worsening of associated paralysis, scoliosis, back pain, and worsening bowel and/or bladder function.
Months or years after myelomeningeal repair, scarring may result in traction on the spinal cord, leading to a tethered cord in at least a third of patients, with symptoms that include back and leg pain and worsening leg, bladder, and bowel function:repeated surgeries often required to release the spinal cord from surrounding scar tissue.
Post operative tethering is different from congeneral tethered cord syndrome in patients with spinal abnormalities, in which skin covers the defect and the abnormalities include tight filum terminale, dermal sinus tract, and split cord malformation.
Many patients with spina bifida have an associated Arnold Chiari II malformation.
Chiarii II Malformation includes herniation of the cerebellum vermis and medulla into the spinal canal, which obstruct the flow of CSF around the lower brainstem causing ventricular dilatation and increased intracranial pressure and cystic dilatation of the spinal cord, syringomyelia.
In about 90% of cases of myelomeningocele, hydrocephalus also occurs.
Hydrocephalus occurs because the displaced cerebellum interferes with the normal flow of cerebrospinal fluid, causing an excess of the fluid to accumulate.
In individuals with spina bifida, especially for those with higher lesion levels, the cerebellum also tends to be smaller.
The corpus callosum is abnormally developed in 70–90% of individuals with spina bifida myelomeningocele, impairing the communication processes between the left and right brain hemispheres.
With myelomeningocele white matter tracts connecting posterior brain regions with anterior regions are less organized.
With myelomeningocele white matter tracts between frontal regions have also been found to be impaired, and cortex abnormalities may also be present:
Frontal regions of the brain tend to be thicker than expected, while posterior and parietal regions are thinner.
Thinner sections of the brain are also associated with increased cortical folding, and neuron displacement.
There are difficulties with executive functions in youth with spina bifida, and greater deficits in those with shunted hydrocephalus.
Youths with spina bifida do not tend to improve in their executive functioning as they grow older: difficulty in some individuals include planning, organizing, initiating, working memory, problem-solving, abstraction, and visual planning
Children with spina bifida may have poor cognitive flexibility.
Individuals with spina bifida, especially those with shunted hydrocephalus, often have attention problems, and higher rates of ADHD.
Infants with spina bifida lag behind their peers in orienting to faces.
Children with spina bifida begin to struggle as academic demands increase.
Children with spina bifida are more likely than their peers without spina bifida to have demonstrated difficulties with arithmetic accuracy and speed, problem-solving, and general use and understanding of numbers.
Mathematics difficulties may be related to the thinning of the parietal lobes, indirectly associated with deformities of the cerebellum and midbrain that affect other functions involved in mathematical skills.
Shunt revisions are associated with poorer mathematics abilities.
Individuals with spina bifida tend to have better reading skills than mathematics skills, and stronger abilities in reading accuracy than in reading comprehension.
Individuals with spina bifida may have difficulty with writing due to deficits in fine motor control and working memory.
After having one child with the condition, or if a parent has the condition, there is a 4% chance the next child will also be affected.
A folic acid deficiency during pregnancy plays a significant role.
Risk factors include certain antiseizure medications, obesity, and poorly managed diabetes.
Those who are white or Hispanic have a higher risk.
Girls are more prone to being born with spina bifida.
Neural arch formation occurs in the first month of embryonic development, often before the mother knows she is pregnant.
Some forms of Spina bifida known to occur with primary conditions that cause raised central nervous system pressure.
Normally the closure of the neural tube occurs around the 23rd and 27th day after fertilization.
Interference of neural tune closure can occur with medications such as some anticonvulsants, diabetes, obesity, and having a relative with spina bifida.
Adding folate to the mother’s diet reduces the incidence of neural tube defects by about 70%, and can also decrease the severity of these defects, if present.
A woman having had one child with a neural tube defect such as spina bifida has about a 3% risk of having another affected child: risk can be reduced with folic acid supplementation before pregnancy.
Recommended amount of folic acid for women of childbearing age and women planning to become pregnant is at least 0.4 mg/day of folic acid from at least three months before conception, and continued for the first 12 weeks of pregnancy.
Women with a prior baby with spina bifida or other type of neural tube defect, or are taking anticonvulsant medication, should take a higher dose of 4–5 mg/day of folate.
Mutations in the gene VANGL1 have been linked with spina bifida in some families.
Fetal ultrasound can detect open spina bifida during pregnancy.
Spina bifida is suggested if the maternal serum alpha-fetoprotein level is elevated and should prompt an ultrasound of the fetal spine and amniocentesis to test for alpha-fetoprotein and acetylcholinesterase.
Spina bifida often results in spontaneous miscarriage, although in the majority of cases, it is an isolated malformation.
Some neural tube defects are associated with genetic disorders such as trisomy.
Ultrasound screening for spina bifida is partly responsible for the decline in new cases: pregnancy termination out of fear that a newborn might have a poor future quality of life.
TREATMENT:
There is no known cure for the nerve damage caused by spina bifida.
Standard treatment is surgery after delivery to prevent further damage of the nervous tissue and to prevent infection.
Surgical care with spina bifida starts with repair of the myelomeningocele to prevent CSF leakage, meningitis, and scarring of the open defect, with treatment of hydrocephalus, to minimize the risk of intellectual disability and death.
Neurosurgeons operate to close the opening on the back, replace the spinal cord and its nerve roots are put back inside the spine and covered with meninges.
A shunt may be surgically installed to provide a continuous drain for the excess cerebrospinal fluid produced in the brain, as happens with hydrocephalus.
There are two forms of prenatal treatment: open fetal surgery, where the uterus is opened and the spina bifida repair performed, and the second is via fetoscopy.
Patients treated with prenatal repair, have improved function of the legs and feet, and lower incidence of hydrocephalus, better mobility, neuropsychological test scores, and independent function, than in postnatal repair groups.
Reabilitation efforts of different therapists and prescribe specific therapies, adaptive equipment, or medications to encourage as high of a functional performance.
Orthopedists monitor growth and development of bones, muscles, and joints.
Neurosurgeons perform surgeries at birth and manage complications associated with tethered cord and hydrocephalus.
Neurologists treat and evaluate nervous system issues, such as seizure disorders.
Urologists to address kidney, bladder, and bowel dysfunction and manage urinary systems with a program of catheterization.
Bowel management programs
Ophthalmologists evaluate and treat complications of the eyes.
Orthotists design and customize various types of assistive technology, including braces, crutches, walkers, and wheelchairs to aid in mobility.
Physical therapists, occupational therapists, psychologists, and speech/language pathologists aid in rehabilitation.
Generally, the higher the level of the spina bifida defect, the more severe the paralysis.
Paralysis does not always occur.
In the United States, rates are higher on the East Coast than on the West Coast, and higher in white people (1 per 1000 live births) than in black people (0.1–0.4 case per 1000 live births).
Immigrants from Ireland have a higher incidence of spina bifida than do natives.
Highest rates of the defect in the USA can be found in Hispanic youth.
The highest incidence rates worldwide were found in Ireland and Wales, where three to four cases of myelomeningocele per 1000 population have been reported.
The reported overall incidence of myelomeningocele in the British Isles was 2.0–3.5 cases per 1000 births.
Outcomes after prenatal spina bifida treatment are improved to the degree that the benefits of the surgery outweigh the maternal risks.
Prenatal repair results:
Reversal of the hindbrain herniation component of the Chiari II malformation
Reduced need for ventricular shunting
Reduced incidence or severity of potentially devastating neurologic effects caused by the spine’s exposure to amniotic fluid, such as impaired motor function.
At one year of age, 40 percent of the children in the prenatal surgery group had received a shunt, compared to 83 percent of the children in the postnatal group.
During pregnancy, all the fetuses in the trial had hindbrain herniation.
However, at age 12 months, one-third (36 percent) of the infants in the prenatal surgery group no longer had any evidence of hindbrain herniation, compared to only 4 percent in the postnatal surgery group.
Fetoscopic repair of myelomeningocele results in far less surgical trauma to the mother, as large incisions of her abdomen and uterus are not required.
The initial punctures have a diameter of 1.2 mm only.
The risks of maternal chorioamnionitis or fetal death as a result of the fetoscopic procedure run below 5%, and women are discharged home from hospital one week after the procedure.
The risk to the mother is small, with the main risk appearing to be preterm labor, on average at about 33 weeks.