The most common physically disabling birth defect in Canada, Spina Bifida affects one out of every 750 children born. It is classified as a neural tube defect (NTD) and occurs during the first four weeks of pregnancy.
Spina Bifida is the incomplete development of the nervous system and spinal cord, and results in varying degrees of permanent paralysis, loss of sensation, and bladder and bowel dysfunction. In some cases, it can also limit hand function, vision, hearing and learning abilities.
The most common types of Spina Bifida are:
Myelomeningocele (or meningomyelocele) is the severest and most common form of spina bifida in which the spinal cord and the meninges (covering of the spinal cord) protrude from an opening in the spine to form a sac (cele). Because the spinal cord leaves the protective bone tube of the spine, damage to the nerves occurs. Urgent treatment is necessary at birth to minimize further neurological damage and infection. Below the opening is where nerve damage can affect development of muscles and limbs. Bowel and bladder function are also frequently affected. In some cases, the skin covering will be absent, requiring surgical closure.
Meningocele is considered a less severe and rarer form of spina bifida. The meninges are pushed out through an opening in the spine to form a sac containing cerebrospinal fluid (CSF), which is often covered by skin. However the spinal cord does not leave the protective bone tube: because the nerves remain protected, they are usually not as severely affected. The person with this form of spina bifida usually has better physical development and bowel and bladder control than one with myelomeningocele.
Lipomyelomeningocele is an abnormal fat accumulation that starts below the skin and extends through an opening in the spine to the spinal cord. The skin covered lesion created is found in the buttock or lower spine area, and is usually not painful. Symptoms, such as muscle weakness or loss of sensation in the lower legs and feet, and bowel or bladder incontinence, occur due to compression of the nerves by the fatty mass (during periods of rapid weight gain) or the attachment of the fat to the spinal cord. Surgery may be required to release the tethering of the spinal cord to the fatty mass (especially during growth spurts) and to reduce the bulk of the fatty tumor.
Occulta, which means "hidden", is the mildest form of spina bifida. A defect exists where one or more vertebrae are not properly closed, but there is no protruding sac or protrusion of the spinal cord. The results of this form of spina bifida may include a sensitive depression (dimple) somewhere along the spine which often has long, dark hairs sticking out of it. Many people have this condition and only become aware of it when they have unexplained incontinence, back ache, or changes in the muscles of their legs. Also, bed wetting may be a problem due to ‘cord tethering’.
People born with spina bifida frequently also have hydrocephalus, however an individual may have hydrocephalus without having spina bifida. Hydrocephalus is a condition in which normal cerebrospinal fluid (CSF) circulation patterns are interrupted. The two most common causes of this are accidents and birth defects, however hydrocephalus can also occur as a result of brain tumors, cysts, scarring, infection, drug reactions and as a part of the aging process.
Approximately 500 mL of CSF is produced daily within the cavities of the brain that are called ventricles. Normally this CSF circulates freely in and around the brain and spinal cord and is reabsorbed from the tissues around the brain into the bloodstream. When the circulatory pathway is blocked, CSF collects in the ventricles causing them to enlarge, which applies increasing pressure on the brain tissue. This excess pressure may result in various symptoms including dizziness, vomiting, severe pain and blurred vision. If left untreated, the pressure on the brain tissue causes the skull to enlarge.
There is no cure for hydrocephalus, however it can be controlled by the surgical insertion of a shunt (a long, flexible tube with a one way valve). A shunt channels the flow of fluid away from the brain or spinal cord into another part of the body, where the CSF can be carried away into the bloodstream.
For a more complete definition of spina bifida or hydrocephalus, please visit the Spina Bifida and Hydrocephalus Association of Canada's web site.