Spina Bifida

Spina Bifida About: Spina bifida (SB) is a neural tube defect (a disorder involving incomplete development of the brain, spinal cord, and/or their protective coverings) caused by the failure of the fetus's spine to close properly during the first month of pregnancy. Infants born with SB sometimes have an open lesion on their spine where significant damage to the nerves and spinal cord has occurred. Although the spinal opening can be surgically repaired shortly after birth, the nerve damage is permanent, resulting in varying degrees of paralysis of the lower limbs. Even when there is no lesion present there may be improperly formed or missing vertebrae and accompanying nerve damage. In addition to physical and mobility difficulties, most individuals have some form of learning disability. SB may also cause bowel and bladder complications, and many children with SB have hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain). There are three types of Spina Bifida: Occulta Often called hidden SB, the spinal cord and the nerves are usually normal and there is no opening on the back. This form is relatively harmless; there is a small defect or gap in a few of the small bones (vertebrae) that make up the spine. There may be no motor or sensory impairments evident at birth. Subtle, progressive neurologic deterioration often becomes evident in later childhood or adulthood. In many instances, SB Occulta is so mild that there is no disturbance of spinal function at all. Occulta can be diagnosed at any age. Meningocele The protective coatings (meninges) come through the open part of the spine like a sac that is pushed out. Cerebrospinal fluid is in the sac and there is usually no nerve damage. Individuals may suffer minor disabilities. Additional problems can develop later in life. Myelomeningocele This form of SB occurs when the meninges (protective covering of the spinal cord) and spinal nerves come through the open part of the spine. This is the most serious type and causes nerve damage and more severe disabilities. Causes: Both genetic factors and environmental factors, such as nutrition and exposure to harmful substances, probably contribute to spina bifida. Spina bifida does seem to run in families, although with mixed patterns of inheritance. Having a child with spina bifida increases the chance that another child will also have spina bifida by 8 times. In about 95% of cases of spina bifida, however, there is no family history of neural tube defects. Research has suggested that many cases of spina bifida can be prevented by adequate intake of folic acid before and during early pregnancy. However, people with spina bifida appear to have abnormal metabolism of folic acid. This suggests that the underlying problem in spina bifida may be an inborn defect in folic acid metabolism rather than a simple deficiency in this nutrient. Pathophysiology: Spina bifida cystica causes a problem when the meningeal cyst (meningocele) includes cord tissue extending into the cyst (in which case, it is a myelomeningocele). The condition is also of particular concern when the neural tube is completely open and the ependymal layer is exposed as a myelocele or myeloschisis. Meningocele alone may cause no neurologic problems if the cord is confined to the vertebral canal. Myelomeningocele is the most common form of spina bifida, accounting for 94% of cases. SBO should be differentiated from spina bifida cystica. The term spina bifida does not refer to SBO. SBO may be seen in a very large number of healthy adults. Some contend that it could be found in up to one third of healthy adults if imaging studies were used to analyze the posterior vertebral arch. Unprotected neural elements are at severe risk during delivery. (Intrauterine surgery, associated with cesarean delivery, has been proposed for cases of spina bifida, with some favorable results reported at

selected centers.) The sequelae of the neural tube defect follow directly from this lack of protection, occurring mechanically or resulting from desiccation, scarring with closure, and/or a lack of vascular support or from other insults to the delicate neural elements. The neurologic damage generally results in a neurogenic bowel and bladder, which leads to incontinence. With a lack of neural input, a contracted bladder causes hydronephrosis along with infections and renal failure, which may be the prime determinant of longevity in patients with spina bifida. As a pattern, neurologic innervation is not symmetrical between lower-limb flexors and extensors, as the corresponding levels are lower (caudal) for the extensors than for the flexors. Generally, muscular imbalance is present, which results in joint contractures and developmental problems, such as hip dislocation and spinal deformities. Normal intelligence can be expected with aggressive shunting for hydrocephalus, although a subtle defect in coordination may be associated with the cerebellar deficiency from the Arnold-Chiari malformation. Seizure activity secondary to the neural tube defect may be noted. Treatment: There is no cure for SB because the nerve tissue cannot be replaced or repaired. Treatment for the variety of effects of SB may include surgery, medication, and physiotherapy. Many individuals with SB will need assistive devices such as braces, crutches, or wheelchairs. Ongoing therapy, medical care, and/or surgical treatments may be necessary to prevent and manage complications throughout the individual's life. Surgery to close the newborn's spinal opening is generally performed within 24 hours after birth to minimize the risk of infection and to preserve existing function in the spinal cord. The many orthopedic procedures used in spina bifida treatment include the following: • Closure of the defect over the spinal cord, without which survival is jeopardized • Spinal deformity reconstruction, which may be particularly challenging because of posterior element deficiencies and can lead to instrumentation and fusion failures, infection from the neurogenic bladder, a closure scar, and ulcers from distal insensate skin • Lower-extremity deformity correction, which is necessitated by muscle imbalance forces Beyond closure, which is a neurosurgical procedure, shunting may be needed for hydrocephalus, including normal-pressure hydrocephalus, and many urologic procedures may be required for the neurogenic bladder.