Neural defects (Spina Bifida)

Introduction:
It is a neural tube defect, defective fusion of one or more posterior arches with resultant protrusion of the spinal canal. Spina bifida is a birth defect affecting the spinal column. It progresses from a cleft or split like opening in the back part of backbones. (The spinal vertebrae).In more severe form, it involves the spinal cord. Spina bifida is the most common group of birth defect known as neural tube defect which affects central nervous system (Brain and spinal cord). Spina bifida begins in the womb, when the tissues fold to form the neural tube, do not stay closed completely. This causes an opening in the vertebra which surrounds & protects the spinal cord. This occurs just a few weeks or 21 to 28 days after conception usually before the woman knows that she is pregnant.

Prevalence:
Incidence of Spina bifida, including Spina bifida occulta is about 0.1%.

General features:

  • People with Spina bifida occulta, are always completely a symptomatic.
  • Various degrees of leg paralysis, spine curvature, hip, foot, and leg deformities & problems with bladder / bowel control.
  • Abnormalities at the lower spine are always accompanied by upper spine abnormality (ARNOLD CHIARI MALFORMATION) causing subtle co-ordination, problems that usually can be improved by physical therapy.
  • Spine, hip, foot, and leg deformities are often due to muscle imbalance.
  • Most common bladder & bowel problems and inability to voluntarily relax the muscles that hold urine in the bladder and stool in the rectum
  • Hydrocephalous affecting about 90% people with Spina bifida
  • Tethered spinal cord -the cord is attached to surrounding tissues and can not move up and down freely as it normally does. This can cause foot / leg deformities, hip dislocation or scoliosis. The problems can worsen as the child grows and tethered cord is stretched.
  • Obesity & urinary tract disorders (due to poor drainage)
  • Pathologic bone fractures occur in as many as 25% of people with Spina bifida.
  • Growth hormone deficiency resulting in short stature people which is common in Spina bifida
  • Although most people with Spina bifida have normal intelligence, may have learning disability.
  • An allergic reaction to latex can be life threatening. (Latex is a natural rubber used in medical gloves, some types of elastic, balloons, and many other common items).
  • Dimple, dark, small hairy patch on the skin overlying the base of spine, other may have a fatty growth called as epidural lipoma, that forms within the spinal cord. This is usually harmless but may result in tethering of spinal cord.

Types
The defect varies in severity from a mere failure of the spinous process, to a bony defect with a major aberration in the development of the neural elements.

  • Spina bifida.occulta
  • Spina bifida cystica
  • Meningocele
  • Myelomeningocele
  • Myelocele
  • Syringocele

Spina bifida occulta

  • Occulta means hidden.
  • Mildest and commonest form
  • Failure of the vertebral arches to fuse results bifid spinous process of the vertebra

Common features
Commonest site:-Lumbo-sacral spine. Externally the skin may be normal or there may be tell-tale signs in the form of a dimple in the skin. Lipomatous mass a dermal sinus or a tuft of hair.  Neurological impairment: Muscle imbalance of the lower limb with selective wasting. This leads to foot deformities common ones being Equinovarus. Equinovarus: Estimates of prevalence from 5% to as high as 40% have been reported.

Spina bifida cystica
There is developmental deficiency of lamina, spinous process, overlying muscles and skin. In severe cases, neural tube may be exposed. It usually involves neurological problems that can be very serious or even fatal. A section of spinal cord and the nerves that stem from the cord are exposed and visible on the outside of body or if there is a cyst. It encloses part of the cord and the nerves. This condition accounts for 94% of cases of true Spina bifida. This is the type of Spina bifida that causes vast majority of disability. Most infants with an open spine or myelomeningocele undergo surgery within the first 48 hours of life to close the defect. Antibiotics are given to prevent infection of the exposed spinal cord and nerves until structures can be protected by surgery. Before antibiotics were available most children born with myelomeningocele died soon after birth those who survive severely disabled. With modern treatment, almost all children survive and having some degree of leg paralysis and often difficulties with bladder and bowel function. Extent of paralysis depends on the part of spinal cord is involved. Higher the defect on the body, more severe the paralysis is. About 80% of myelomeningocele occurs in the lumbar and sacral regions of spine.

Meningocele
In this variety, occasionally the spinal cord & its nerve roots are contact and the covering membrane projects as a dural sac. If this defect is closed by early surgery, paralysis can be avoidable and habilitation is easy.

Mylomeningocele
Spinal cord is exposed to the surface as a plaque or nervous tissue. It is associated with muscles paralysis, sensory loss, bladder & bowel incontinence and deformities .It may be present from 4th thoracic to 1st sacral vertebra. This is associated with usual complications, paraplegia, bladder and kidneys infections, skin ulceration etc. Pathological fracture, meningitis, and hydrocephalous are also common.

Myelocele
This type of Spina bifida results from an arrest in development at the time of closure of the neural groove. This is the commonest type of Spina bifida.

Syringocele
Central canal of the cord is dilated and the cord lies with in the protruded meningeal sac together with the nerve arising from it.

Associated factors:
Most common birth defect historically occuring in 1 per 1000 live birth. The rates of Spina bifida are higher in Hispanics, and significantly among couples who have already had a child with spinal bifida.

Common Causes
Genetic factors & Environmental factors, nutrition & exposure to harmful substance probably contribute to Spina bifida. Having a child with Spina bifida increases the chances that another child will also have Spina bifida by 8 times. People with Spina bifida appear to have abnormal metabolism of folic acid. This suggests that underlying problem in Spina bifida may be inborn error in folic acid metabolism rather than a simple deficiency in this nutrient.

Examinations and Tests:
Prenatal test measures the level of maternal serum fetoprotein. This is usually high in women carrying a fetus with Spina bifida or other neural tube defects.
Triple Screen: It includes AFP, Ultrasound, and Testing of Amniotic fluid. CT- Scan and MRI.

Treatments:
Treatment for Spina bifida depends on the severity of the condition.

  • Most people with Spina bifida occulta require no treatment at all.
  • Children with meningocele requires removal of the cyst, is survived with little of any disability.
  • Children with myelomeningocele require complex and life long treatment & assistance.
  • Special care is required for myelomeningocele child.
  • Immediately transferred to a centre where newborn surgery can be performed.
  • Treatment with antibiotics started as soon as possible for myelomeningocele. Because it prevents infection of the spinal cord which can be fatal.
  • The operation involves closing the opening in the spinal cord & covering the cord with muscles and skin taken from either side of the back. Most common complications are tethered spinal cord & hydrocephalous, which can have very severe consequences.
  • Care team includes pediatricians, neurologist, neurosurgeons, orthopedic surgeons, physical medicine specialist, endocrinologists, urologists, Therapists, psychiatrists, Orthoses specialists, nurses, dietician, social workers, other professionals.
  • There is no cure for Spina bifida. The goal of treatment for Spina bifida is to allow the individual to achieve the highest possible level of functioning & independence. .

Medical Treatment:
After newborn surgery, children with severe Spina bifida undergo regular assessment to detect any deformities, developmental problems or other complication that may require intervention. Children should be watched for signs of hydrocephalous, tethered spinal cord, seizure activity, obesity, bowel and bladder control problem, frequents urinary tract infections, learning problems, emotional-psychosocial problems & other complications of Spina bifida. Care should be taken that early detection of these complications. .

THE FOCUS OF TREATMENT IS DEVELOPING STRENGTH, MOBILITY & INDEPENDENCE.:

Parents should work with a therapist to learn how to exercise the body and legs to maximize strength & movement. They should begin with these exercises as soon after the first surgery as possible. This not only readies the child for walking, but also prevents osteoporosis due to disuse. Children with Spina bifida should be provided with prolonged physical education or adaptive training. Many children can become mobile by wearing a brace / using crutches or an orthotics aid. These devices allow the child to function at the best possible level by helping with balance, posture & control.
Despite, the assistance, some children of Spina bifida will never be able to walk independently. These children will use a wheel chair for the rest of their lives.
Bowel and Bladder can cause not only physical problems but also social problems due to teasing, rejection, & isolation.

Children can be taught techniques for emptying their bladder and bowel appropriately & independently, thus avoiding embarrassment.
For example-use of a plastic tube to drain urine from the bladder on a regular schedule can help prevent overfilling which can injure the kidneys. This technique called as CLEAN INTERMITTENT CATHETERIZATION, is of proven benefit in people with Spina bifida. Prevention of obesity is an important aspect of medical care for person with Spina bifida. Education aspect & counseling physical activity & dietary choices can help maintain weight in a healthy level.

Treatment for other complications of Spina bifida depends on the nature of the complication. Medications, Surgery, Physical therapy, or behavioral therapy may be appropriate.

Surgical Treatment:
Surgery is the most common treatment for Spina bifida & its complications. Most children with severe form need a series of operations.

First, which is usually done in the first 48 hours of life, involves tucking the expose cord & nerve roots back into the surrounding membrane closing the defects in cord & membrane & covering the wound with muscle & skin flaps taken from either side of the back. Subsequent, surgeries involve correction of deformities. This might includes cutting tendons or ligaments to release contractures, and rebalancing muscles around the involved joints. When regular examinations indicate that the individual's functioning is declining while a physical deformity gets worse, surgery should be considered.

 

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