Spina Bifida: Types and Overview

Spina Bifida Overview

• Spina Bifida is a collective term for spinal cord disorders
• This condition arises from the incomplete fusion of the embryo's posterior surface during early intrauterine development
• The Latin word for Spina Bifida is "divided spine"
• Incidence ranges between 1 to 10 cases per 1,000 live births
• Incidence decreases with Folic Acid 600 mcg in prenatal vitamins and mandatory inclusion of Folic Acid in all cereal and grain products
• Folic acid inclusion reduces the rate to 2 in 10,000 live births
• Maternal age is a risk factor if under 20 years, as is low socioeconomic status
• Women who have given birth to a child with a spinal cord disorder are advised to have MAFP levels assessed during a second pregnancy

Types of Disorders

• Anencephaly is where absence of cerebral hemispheres occur
• Microcephaly is where the fetal brain grows so slowly that it falls more than 3 standard deviations below normal on a growth chart at birth.
• Spina Bifida Occulta is where the posterior laminae of the vertebrae fail to fuse
• Meningocele involves membranes that herniate through an unformed vertebra
• Meningomyelocele is where the spinal cord usually ends at the point of protrusion, but not just the meninges protrude through the vertebrae
• Encephalocele is a cranial meningocele

Anencephaly

• The upper end of the neural tube fails to close in early intrauterine life in cases of Anencephaly
• Elevated MAFP levels, amniocentesis, or a prenatal sonogram can reveal this condition
• Labor might be prolonged due to breech presentation or the underdeveloped head not engaging the cervix properly
• Visual inspection can easily identify the disorder
• Infants may survive for a few days due to the intact medulla housing respiratory and cardiac sphincters, but survival is limited due to lacking cerebral function
• Support is needed in the first few days as caregivers realize the baby is ill and incomplete as predicted

Microcephaly

• Microcephaly is a disorder where the fetal brain grows more slowly thus falling below normal on a growth chart at birth by more than 3 standard deviations
• Potential causes include brain development disorders associated with intrauterine infections like Rubella, Cytomegalovirus, or Toxoplasmosis
• It may result from severe malnutrition or anoxia following birth or in early infancy
• Infants are generally cognitively challenged due to insufficient functioning brain tissue

Spina Bifida Occulta

• Spina Bifida Occulta stems from the failure of the posterior laminae of the vertebrae to fuse
• This commonly occurs at the fifth lumbar or first sacral level, also may occur anywhere along the spinal canal
• Dimpling at the point of poor fusion may be the first indication
• Abnormal tufts of hair or discolored skin might appear
• Simple Spina Bifida Occulta is a benign condition affecting approximately one in four children
• Parents should get clarification that a surface of bone is missing, but the spinal cord remains intact

Meningocele

• The spinal cord is protected by three layers of meninges or membranes, including the Pia Mater, Arachnoid, and Dura Mater
• Meningocele occurs when membranes herniate through an unformed vertebra, protruding as a circular mass about the size of an orange at the center of the back
• Protrusion typically occurs in the lumbar region but could be anywhere along the spinal cord
• The protrusion might be covered by a layer of skin or only the clear dura mater
• Sensory or motor deficits are typically absent unless the membrane sac ruptures, leading to potential cord damage and infection

Meningomyelocele

• Meningomyelocele affects the CNS, it is the most common birth defect
• The spinal cord usually ends at the point of protrusion, more than just the meninges protrude through the vertebrae
• Motor and sensory function is diminished or absent beyond this point
• Affected children experience partial or complete paralysis, also they lack sensation in the lower extremities, as well as loss of bowel and bladder control
• Urine and stools continually dribble because of a lack of sphincter control
• Hydrocephalus develops because of the lack of an adequate subarachnoid membrane for CSF absorption and obstruction of CSF circulation from the spinal deformity in approximately 90% of infants
• The higher the Meningomyelocele occurs on the cord, the more likely it is that a hydrocephalus will accompany it

Encephalocele

• Encephalocele classifies as a cranial meningocele
• Occurs most often in the occipital area of the skull but may occur as a nasal or nasopharyngeal disorder
• It typically is covered fully by skin, although they may be open or covered only by the dura mater
• Transillumination of the sac can reveal whether brain tissue is in the sac
• CT, MRI, or ultrasound scans help assess the size of the skull disorder and predict the extent of surgery

Assessment of Neural Tube Disorders

• Neural tube disorders may be discovered during intrauterine life via prenatal ultrasound, fetoscopy, amniocentesis for AFP in amniotic fluid, or analysis of MAFP
• A Cesarean birth is used to avoid pressure and injury to the spinal cord
• Observe and record whether an infant born with a neural tube disorder has spontaneous movement of the lower extremities to assess lower motor function
• Assess the nature and pattern of voiding and defecation
• The usual newborn appears to be "always wet" from voiding
• An infant without motor or sphincter control voids continually

Therapeutic Management

• Children with Spina Bifida Occulta need no surgical correction because there is no tissue extruding from the vertebrae
• Parents should be aware of the defect and watch for symptoms of numbness, weakness, or pain which might indicate if a reevaluation is needed
• Children may need surgery eventually to prevent vertebral deterioration because of an unbalanced spinal column
• Treatment for Meningocele or Encephalocele involves immediate surgery to replace the meninges and close the gap in the skin to prevent infection
• This is done as soon as after birth (usually 24 to 48 hours) so an infection through the exposed meninges does not occur
• Removing a large portion of meninges by surgery can limit the rate of absorption of CSF, potentially causing a buildup of CSF and Hydrocephalus
• Children with meningomyelocele have surgery to return the meninges to the spinal cord and close the gap in the skin surface
• The child will continue to have partial or complete paralysis of the lower extremities and loose bowel and bladder function because the absent lower cord cannot be replaced, even when the lesion is repaired
• AFP - more than twice if there is a neural tube disorder
• Decrease-chromosomal disorders such as Trisomy 21