The human nervous system originates from a specialized plate of cells (the neural plate) along the dorsal aspect of an embryo. During the early embryonic development the edges of neural plate start to fold, forming the neural tube. The neural tube closes to form the brain and spinal cord in the embryo. During the developmental period, the upper end of neural tube becomes the brain and the remainder forms the spinal cord. This process of forming the central nervous system is usually completed by the 28th day of gestation. Problems in the formation of the neural tube give rise to neural tube defects (NTD’s): SB is one of those defects. SB also called ‘cleft spine’ occurs due to inadequate development of the spinal cord and/or meninges. SB is the most common NTD in the United States, affecting almost 1,500 to 2,000 of the more than 4 million babies born in each year. The current estimated number of patients with SB living in United States are 166,000 . Supplementation with folic acid during pregnancy decreases the incidence of NTD’s.
SB can be classified into following classes:
- Open Spina Bifida (it includes SB occulta and SB cystica)
- Closed SB /neural tube defects (spinal cord Lipoma, lipomengocele, etc.)
SB occulta is the most common and also the least severe form of SB, which is characterized by the malformation of one or more vertebrae. The term “occulta” means that the malformation or defect in the spine is covered by a layer of skin. The incidence of this form of SB is 10 to 20 percent in the general population. It rarely causes neurological complaints or symptoms .
SB cystica is characterized by herniation of spinal fluid and the meninges through an abnormal vertebral defect. This birth defect contains no neural tissue and may or may not be covered by a layer of skin. It can be further classified into two forms :
- Meningocele- is characterized by herniation of the cystic sac (containing only meninges without spinal tissue) through an abnormal opening in the vertebral column. It usually causes none or limited disability in infants, although complications can develop in later life.
- Myelomeningocele- is characterized by protrusion of the meninges as well as underlying spinal cord through an abnormal vertebral defect into a cystic sac. It is the most severe form and can cause disability in 99% of patients. The severity of the problem depends on the level of the spinal lesion, which may be found anywhere along the back-bone but most commonly in the lumbosacral area. Myelomeningocele can cause multi- organ disorders, involving the skin, urinary bladder, gastro-intestinal tract, bones, peripheral and central nervous system .
Causes of open spina bifida
It is an abnormality in the closure of the neural tube that leads to it or other NTDs. The exact cause of it and others NTDs is still not known. Some scientists suspect that the following factors are involved in causation of such defects:
- Genetic factors- a woman with the history of a previous baby with NTD’s has more chances to have another baby with NTD’s.
- Environmental factors
- Exposure to certain drugs
- Folic acid deficiency [3,4]- folic acid supplementation during antenatal period decreases the incidence of the development of NTD’s .
Signs and symptoms of open spina bifida
The clinical presentation of it depends upon its type. The patient can present with following signs and symptoms:
- Difficulty in walking
- Poor coordination in walking
- Urinary frequency, urgency and incontinence
- Urinary retention
- Constipation and diarrhea
- Some infants may also develop hydrocephalus. It can cause seizures, intellectual disability and sight problems.
- An allergy to latex products
- Paralysis of lower limbs
- Numbness of lower limbs
- Pain and heaviness in lower limbs
- Loss of sensation in the genital area .
Diagnosis of open spina bifida
Prenatal diagnosis can be made by performing the following investigations:
- Alpha fetoprotein levels
- Serum folic acid levels
- Quadruple/triple screen
Postnatal diagnosis can be made by running the following tests or investigations:
- History and physical examination of the patient
- X-rays of the spine
- MRI- of the spine
- CT-Spine .
Treatment of open spina bifida
Treatment of it depends upon its type. Surgery is not carried out in case of spina bifida occulta. In the case of myelomeningocele and meningocele, a repair surgery is performed. Supportive treatment is given to patients with irreversible neurological deficits .
Open Spina Bifida is a class of neural tube defect which is further sub-divided into various types. Its clinical presentation varies depending upon its subtype. In most of the cases, its treatment is surgery. A delay in surgery can cause irreversible neurological deficits. Thus in order to avoid complications NTD’s must be diagnosed and managed as early as possible.
- Fletcher JM, Brei TM. Introduction: SpinaBifida—A Multidisciplinary Perspective. Dev Disabil Res Rev 2010:16(1):1-5.
- Northrup H, Volcik KA. Spinabifida and other neural tube defects. Curr Probl Pediatr 2000;30(10):313-32.
- Groenen PM, Klootwijk R, Schijvenaars MM, et al. Spinabifida and genetic factors related to myo-inositol, glucose, and zinc. Mol Genet Metab 2004;82(2):154-61.
- Ahrens K, Yazdy MM, Mitchell AA, Wereler MM. Folic acid intake and spinabifida in the era of dietary folic acid fortification. Epidemiology 2011;22(5):731-7.
- Sandler AD. Children with spinabifida: key clinical issues.Pediatr Clin North Am 2010;57(4):879-92.
- Myelomeningocele [Internet]. [Last updated 15 Mar 2004; Cited on 30 Oct 2013]. Available from: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002525/.
- Main MD, Mennuti MT. Neural tube defects: issues in prenatal diagnosis and counselling. Obstet Gynecol 1986;67(1):1-16.
- Manning SM, Jennings R, Madsen JR. Pathophysiology, prevention, and potential treatment of neural tube defects. Ment Retard Dev Disabil Res Rev 2000;6(1):6-14.