Overview
Spina Bifida
Spina bifida is a Latin term that literally means 'split spine'. It is a developmental birth defect that is associated with the incomplete closure of the embryonic neural tube resulting in an incompletely formed spinal cord. In humans, there are usually 33 vertebrae in the spine - if one or more of these are improperly formed in early pregnancy, the nerves of the spinal cord maybe unprotected and may lead to damage of the central nervous system.
Also, the vertebrae overlying the unclosed portion of the spinal cord do not form correctly and remain unfused, allowing the abnormal portion of the spinal cord to protrude through the opening in the bones. This particular open part of the spinal cord may or may not contain a surrounding fluid filled sac.
There are three major types of spina bifida:
- Spina bifida occulta
- Spina bifida meningocele
- Myelomeningocele.
Spina bifida occulta
Occulta is latin for 'hidden'. This is the most common and mildest forms of spina bifida, although the degree of disability can vary depending on the location of the lesion. With this type, there is usually no opening in the spine but the outer part of some of the vertebrae are not entirely closed. These slits or gaps are so small that the spinal cord cannot protrude. The surrounding skin at the site of the lesion may be normal or hair growth from it may be present otherwise.
Many people with spina bifida occulta are unaware of that they have this condition or symptoms do not appear until later in life.
Spina bifida meningocele
This is the least common type of spina bifida. Normal development of the spine is observed, but the protective membranes are forced out between openings in the vertebrae discs therefore appearing as a sac or cyst which contains cerebrospinal fluid. In addition, the cyst could protrude towards the inner faces of the vertebrae into the retropritoneum or the presacral space. These membranes can usually be easily removed during surgery, and no further treatment is required.
A person born with spina bifida meningocele has no negative long-term effects as the nervous system remains undamaged, although there are reports of a tethered cord.
Myelomeningocele
Myelomeningocele (also known as spina bifida cystica) is the most serious type of spina bifida. It has an estimated prevalence of 1 in every 1,000 births worldwide.
In this form of spina bifida, there is usually an unfused portion of the spinal column, along several vertebrae, allowing the spinal cord to protrude through the opening overlying the vertebrae. Protective membranes generally do not form a sac enclosing the spinal elements, therefore presenting the nervous system to life-threatening infections.
In some rare cases of myelomeningocele, the spinal cord can be repaired using surgery. However, there is usually extensive damage to the nervous system already, leaving some degree of paralysis and loss of sensation below the level of the neural tube defect.
Anencephaly
This type of NTD occurs when the 'cephalic' or head region of the neural tube fails to close, resulting in the absence of a major portion of the brain, skull and scalp. This causes limited development of the brain, and people who have this disorder often lack part or all of the cerebrum (the region of the brain responsible for thinking and coordination). The remaining part of the brain usually lacks a bony covering and therefore is exposed.
A newborn suffering from this disorder are often blind, deaf, unresponsive to pain sensations and due to the lack of a functioning cerebrum, may never be able to gain consciousness. However, reflex actions such as breathing, touch or sound relfexes may remain present.
In the United States alone, research shows there is an estimated 1500 babies born with anencephaly per year and overall, a higher occurence in female babies.
X-ray image of spina bifida. Image courtesy of https://en.wikipedia.org/wiki/File:IMG_0746a.jpg. Public domain image.