Spina bifida (Latin: "split spine") is a developmental birth defect involving the neural tube: incomplete closure of the embryonic neural tube results in an incompletely formed spinal cord. In addition, the vertebrae overlying the open portion of the spinal cord may not fully form and remain unfused and open. This allows the abnormal portion of the spinal cord to stick out through the opening in the bones. There may or may not be a fluid filled sac surrounding the open spinal cord. Other neural tube defects include anencephaly, a condition in which the portion of the neural tube which will become the cerebrum does not close, and encephalocele, which results when other parts of the brain remain unfused.
Different types of spina bifida:
There are four types of spina bifida:
- closed neural tube defects,
- meningocele, and
Occulta is the mildest and most common form in which one or more vertebrae are malformed. The name "occulta," which means "hidden," indicates that the malformation, or opening in the spine, is covered by a layer of skin. This form of spina bifida rarely causes disability or symptoms.
Closed neural tube defects make up the second type of spina bifida. This form consists of a diverse group of spinal defects in which the spinal cord is marked by a malformation of fat, bone, or membranes. In some patients there are few or no symptoms; in others the malformation causes incomplete paralysis with urinary and bowel dysfunction.
In the third type, meningocele, the meninges protrude from the spinal opening, and the malformation may or may not be covered by a layer of skin. Some patients with meningocele may have few or no symptoms while others may experience symptoms similar to closed neural tube defects.
Myelomeningocele, the fourth form, is the most severe and occurs when the spinal cord is exposed through the opening in the spine, resulting in partial or complete paralysis of the parts of the body below the spinal opening. The paralysis may be so severe that the affected individual is unable to walk and may have urinary and bowel dysfunction.Symptoms of Spina bifida:
In spina bifida occulta, which affects up to one in ten people, there may be visible signs of a dimple or small hair growth on the back. Often people don’t even know that they have it and it is noticed on an xray that is taken for another reason. This is a mild form and rarely causes disability.
In spina bifida cystica there is a sac or cyst (like a blister) on the back, covered by a thin layer of skin. The sac contains tissues that cover the spinal cord, cerebrospinal fluid and sometimes even the nerves and tissues of the spinal cord itself.
There are two forms of spina bifida cystica:
Meningocele - the sac contains tissues that cover the spinal cord (meninges) and cerebrospinal fluid. Nerve damage is minimal, so there's often little disability.
Myelomeningocele - the sac contains tissue, cerebrospinal fluid, nerves and part of the spinal cord. Spinal cord damage or incomplete development always occurs, resulting in paralysis and sensation loss below the damaged region. Many lose the ability to walk as they grow.
There's often an accompanying condition called hydrocephalus (increased pressure in the fluid in the brain, which causes some very young children's heads to swell with the pressure), which can gradually damage brain function especially if untreated. Other problems include incontinence and urinary tract infections.
Myelomeningocele is more common and more serious than meningocele.
Complications of spina bifida:
Complications of spina bifida can range from minor physical problems to severe physical and mental disabilities. It is important to note, however, that most people with spina bifida are of normal intelligence. Severity is determined by the size and location of the malformation, whether or not skin covers it, whether or not spinal nerves protrude from it, and which spinal nerves are involved. Generally all nerves located below the malformation are affected. Therefore, the higher the malformation occurs on the back, the greater the amount of nerve damage and loss of muscle function and sensation.
In addition to loss of sensation and paralysis, another neurological complication associated with spina bifida is Chiari II malformation—a rare condition (but common in children with myelomeningocele) in which the brainstem and the cerebellum, or rear portion of the brain, protrude downward into the spinal canal or neck area. This condition can lead to compression of the spinal cord and cause a variety of symptoms including difficulties with feeding, swallowing, and breathing; choking; and arm stiffness.
Chiari II malformation may also result in a blockage of cerebrospinal fluid, causing a condition called hydrocephalus, which is an abnormal buildup of cerebrospinal fluid in the brain. Cerebrospinal fluid is a clear liquid that surrounds the brain and spinal cord. The buildup of fluid puts damaging pressure on the brain. Hydrocephalus is commonly treated by surgically implanting a shunt—a hollow tube—in the brain to drain the excess fluid into the abdomen.
Some newborns with myelomeningocele may develop meningitis, an infection in the meninges. Meningitis may cause brain injury and can be life-threatening.
Children with both myelomeningocele and hydrocephalus may have learning disabilities, including difficulty paying attention, problems with language and reading comprehension, and trouble learning math.
Causes and Risk Factors of Spina Bifida:The most important risk factor for spina bifida is poor nutrition, especially a diet deficient in folic acid.
There appears to be factors other than nutrition in the development of spina bifida. Genetics also seems to play a role. People of Northern European and Hungarian ancestry have the highest rates of the disease, and the condition tends to run in families, though not consistently. In fact, 90 to 95 percent of children with spina bifida are born to women who have no other children or anyone in the family with the defect.