Spina bifida is one of the leading causes of childhood disabilities. Many babies with this defect survive but many suffer illness, lifelong disability and social challenges. The resulting medical and special education costs are staggering; the emotional and financial drain for the families can be devastating. Because of these reasons spina bifida is a birth defect of immense importance.
The introduction of screening programmes measuring maternal serum alfa fetoprotein levels and the development of more sensitive ultrasound scanners have made possible antenatal diagnosis at stage when termination of pregnancy can be offered. "Prevention is better than cure". In the West, it has been proved that folic acid supplementation in the periconceptional period of women has reduced the incidence of NTDs by 70%. Special attention has to be given and effective campaign should be started in our country for prevention of this congenital malformation.
What is spina bifida? How does it occur? "Spina Bifida" comes from 2 words "Spina" meaning spine, "bifida" meaning split or divided. Spina bifida is the term used to describe a birth defect resulting from abnormal fusion of the posterior neural tube. The etiology is unclear. Though many factors including familial (hereditary), genetic and environmental factors - folic acid & zinc deficiencies, lead excess, maternal hyperthermia, hypervitaminosis A, excessive potatoes, hormones during conception, parenteral smoking and insulin dependent DM in mother have been proposed no definite etiological factor has been gained rational explanation in the causation of the spina bifida. Amongst these etiological factors maternal folic acid deficiency is the most renowned fact which many authors agree as a cause for spina bifida.
Characteristically in spina bifida, the change ranges from one or more vertebrae being incompletely developed with a minimal abnormality such as an absent spinous process and associated dorsal intralaminar cleft to the more profound changes of absence of the dorsal half of the vertebrae at multiple levels, abnormal vertebral bodies and high degree kyphosis. In it's full expression such as myelomeningocele the entire central nervous system is involved and there are associated multi system anomalies.
Types of spina bifida
Spina bifida occulta
Spina bifida occulta refers to a vertebral anomaly consisting of the absence of spinous process and varying amounts of the associated lamina. Usually the central nervous system, cauda equina and meninges are not involved. The neurological examination is normal. Most frequently the skin is normal over the vertebral defect however, associated dimples, sinuses, hypertrichosis (increased hair), fatty lump and hemangiomata (swelling consisting of blood vessels) may indicate the presence of occult lesion.
Spina Bifida Aperta
Meningocele: Meningocele becomes evident at birth with observation of a cystic skin covered midline mass over the back. The dorsal half of one or more vertebrae is absent and the sac is composed of CSF, meninges and skin. The reminder of the CNS is not involved and the prognosis for development is excellent. About 10% of the patients with spina bifida will have meningocele.
Myelomeningocele: Myelomeningocele is most severe form of spina bifida. The middle mass in addition to CSF and meninges contains spinal cord and cauda equina. All of these patients will have Arnold Chiari malformations; most of them will develop hydrocephalus. There is sensory motor loss distal to the lesion which produces neurogenic bladder and varying degree of weakness in lower limbs. Orthopedic deformities are commonly present.
Lipomyelomeningocele: Refers to lesions as described above that are associated with a lipoma. This may be extradural and /or intradural and involve the cauda equina and the conus medularis.
Rachischisis: describes the failure of ectodermal and mesodermal closure that results in the brain and spinal cord being exposed to the environment.
Neural Tube Defect- Burden
Neural tube defect is the most common congenital malformation of central nervous system. However its prevalence varies greatly from place to place, population to population. The highest incidence of NTD has been reported from Ireland and Wales (6.38-14.92 per 1000 births) whereas it's incidence in other European countries has been only 0.1-0.6 per 1000 births. The prevalence of NTD in the US and worldwide is about 1 per 1000. Other parts of the world with high prevalence of NTD are northern India, Northern China, Egypt and Lebanon. Its prevalence in Palestinians too has reported to be high. Interestingly compared to northern provinces in China the prevalence of NTD in southern China is only 1 per 1000. Its prevalence in Japan is also low.
The prevalence of NTD from different parts of India has been reported to vary from 0.5 to 11 per 1000 births. In general the prevalence in northern states namely Punjab, Delhi, Haryana, Rajasthan, UP and Bihar has been much higher (3.9 to 9 per 1000) compared to eastern, western and southern parts of country (0.5-2.64 per 1000). One exception to this statement is the reported high incidence of NTD from Davangere in Karnataka (8-9). With this data if we take the incidence of spina bifida to be 5-7, then with present rate of population increase; around 107814 newborns are born every year with NTD in India.