Incomplete closure of neural tube during embryonic life leads to the well known developmental congenital defect termed as spina bifida (SB). In this defect some of the vertebrae of the spinal cord are not completely formed and remain open. The opening may or may not allow spinal tissue to bulge through it. Spina bifida anomalies can be divided into three main groups:
- Spina bifida occulta (SBO)
- Spina bifida cystic with meningocele
- Spina bifida cystic with myelomenengiocele
The most common location of these congenital anomalies is the lumber or the sacral areas. The incidence of SB is almost one in every 1000 births. The SBO occurs when there is incomplete closure of some vertebrae in the lunbosaccral region without protrusion of the spinal cord or the menengies.
SBO is the mildest form of SB and is often termed as hidden spina bifida. At least one vertebra is malformed in this anomaly without involvement of the nerves or spinal cord. This form of spina bifida is common: It occurs in almost 5% of the population. It can be recognized externally by the presence of a skin depression or dimple, tuft of hair, telengiectasis or lipomas on the lower back.
No neurological deficit is usually associated with this anomaly. However, abnormal adhesions of the spinal cord to the involved area may be present which can give rise to sensory, motor and autonomic disturbances1-4.
Causes and Risk Factors
The exact cause of spina bifida occulta is not known. However, recent studies suspect that the cause of this defect is multifactorial. The possible causes may include:
- Genetic factors
- Nutritional deficiencies
- Environmental factors
- Low intake of folic acid by the pregnant mother
The possible specific risk factors for this disorder include:
- Maternal age- this anomaly is more commonly seen in newborns of teenage mothers
- Birth order- the first baby is at higher risk of developing this disorder
- History of miscarriage
- Lower socioeconomic status
- Low level of folic acid
- Uncontrolled diabetes in mother especially during early part of pregnancy increases the risk of developing this anomaly.
- Presence of neural tube defect in a previous child
- Use of some medications like anti-epileptics during pregnancy is another risk factor1, 2, 3.
Forms, clinical features and mild spina bifida occulta s1 complications
There may be different forms of spina bifida occulta. These include:
- Lipomenengocele- this form is like a tethered spinal cord, except it is attached to a benign tumor of fatty tissue
- Thickened filum terminale
- Fatty filum terminale
- Diastematomyelia- the split spinal cord
- Diplomyelia- splitting of spinal cord into two halves by a piece of bone or cartilage
- Dermal sinus tract
In spina bifida occulta there is no problem with the spinal cord or nerves, so usually it is asymptomatic except for the presence of skin manifestations such as the presence of a tuft of hair, lipomas, and depressions on the lower back. However, clinical manifestations may be present if there is an abnormal adhesion of the spinal cord with the involved area or if SBO complications are present. Some of the spina bifida occulta complications include:
- Tethered cord syndrome- it is the most frequently seen complication. It is one of the causes of spina bifida occulta back pain. Other features include weakness of the lower limbs, numbness, ataxia, and a dysfunctional bladder and bowel.
- Foot deformity
- Lower limb paralysis
- Bladder and bowel dysfunctions
- Bladder infections
- Dermal tract sinus and its infection
- Loss of sensations
- Adhesions of spinal cord with the lesion1,2,4-6.
This anomaly can be diagnosed by its clinical features and by investigations like x-rays and MRI. Most of the time, it remains undetected. The clinical features that can be used to diagnose this anomaly are:
- Tuft of hair on the middle or lower back
- Lipoma on the lower back
- Hpopigmented areas on the lower back
- Skin dimples on the lower back
- A reddish or purple spot
- A sinus above the level of crease of the buttocks
- A small tail
- Clinical features of complications like pain in the legs, weakness of the lower limbs, urinary and bowel complaints, loss of sensation, etc2, 4, 6.
In most instances no treatment is needed. If complications are present, they are treated according to the following techniques or procedures:
- Untethering of the cord in case tethered cord
- Separation of adhesions if present
- Antibiotics for bladder infections
- Drugs for pain, bowel and urinary complaints
- Davies RW. Congenital vertebral anomalies: aetiology and relationship to spina bifida cystic. J Med Genet 1975;12(3):280-8.
- Moris G. Adult Complications of Spina Bifida Occulta. [internet]. [last updated 2011 Mar 25; cited 2013 Aug 23]. Available from:http://www.livestrong.com/article/244091-adult-complications-of-spina-bifida-occulta/.
- Lorber J, Levick K. Spina bifida cystica. Incidence of spina bifida occulta in parents and in controls. Arch Dis Child 1967;42(222):171-3.
- Spina Bifida Occulta [internet]. [cited;2013 Aug 23]. Available from:http://nervous-system.emedtv.com/spina-bifida-occulta/spina-bifida-occulta-p2.html.
- Lapsiwala SB, Iskandar BJ. The tethered cord syndrome in adults with spina bifida occulta. Neurol Res 2004;26(7):735-40.
- Craig WM, Mulder DW. Late neurologic symptoms of spina bifida occulta: report of a case. Proc Staff Meet Mayo Clin 1956;31(4):98-100.