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Spina Bifida Occulta

Caudal Dysplasia

Spina bifida occulta is a form of spina bifida, in which the neural defect is hidden completely under the skin. Telltale signs of the defect can be seen in some affected individuals on close observation.


Presentation

Although neurological deficits are generally absent in this condition, some patients may present developmental abnormalities. This includes spinal cord lipoma or a fibrous cord and may result in rare neurological signs. The most common symptoms of this condition include dermatologic manifestations above the abnormality like:

  • Depression or dimple 
  • Presence of tuft of hair
  • Soft fatty deposits 
  • Port wine nevi

All of these are seen on the skin covering the spinal defect. But in many patients such defects may be totally absent. Some of the not so common manifestations include incontinence, foot deformities, weakness of the lower limbs, loss of reflexes, and numbness of the legs. Many patients complain of back stiffness and pain. Some present with sensitivity at the region when pressure is applied. These signs may be present at birth, but may also develop later in life.

Primary Amenorrhea
  • Patients usually presents with primary amenorrhea with underdeveloped secondary sex characteristics. Phenotypes of these patients are female.[ncbi.nlm.nih.gov]

Workup

Blood tests and amniocentesis are generally used to identify the neural tube defects. These tests are usually used in combination with fetal ultrasonography. Prenatal diagnosis helps the person to prepare for appropriate care in case of confirmation of any type of spina bifida. Maternal blood levels of alpha fetoprotein (AFP) may show possible neural tube defects. About 90% of the neural defects can be detected with the combination of serum AFP levels and fetal ultrasonography. This is usually done during 20th week of gestation. Ultrasonography may not be sensitive enough to accurately identify the location of defect.

Spina bifida occulta may or may not be visible on physical examination. X-ray is the most commonly used diagnostic technique in this condition. Pin-prick examination of the legs and trunk enables to show the level of sensory and motor involvement. Some other postnatal measures for diagnosis of this condition include detection of neurological symptoms, visual inspection of spine, and spinal ultrasound. In many cases, when the child is asymptomatic, the condition may remain undiscovered until sought for.

Magnetic resonance imaging (MRI) improves the diagnosis of occult spinal disorder, particularly when plain radiographs are not clear with the lesions [8]. This is useful in detecting tethered cord, diastematomyelia, syringocele, and diplomyelia. To evaluate functionality, gait analysis may be conducted. This helps to identify defects in muscle innervation, strength, and coordination patterns.

Neurophysiologic Abnormalities
  • No significant correlation was found between any particular neurophysiological abnormality and the presence of spina bifida.[ncbi.nlm.nih.gov]
Neurophysiological Abnormalities
  • No significant correlation was found between any particular neurophysiological abnormality and the presence of spina bifida.[ncbi.nlm.nih.gov]
Candida
  • […] kidder, whydah • bewilder , builder, guilder, Hilda, Matilda, St Kilda, Tilda, tilde • Belinda , Cabinda, cinder, Clarinda, Dorinda, hinder, Kinder, Linda, Lucinda, Melinda, tinder •Drogheda • shipbuilder • bodybuilder •coachbuilder • boatbuilder • Candida[encyclopedia.com]

Treatment

The main aim of treatment is to improve the symptoms of the condition. Spina bifida occulta may require prudent monitoring during the growth and development of the child. Treatment, if needed, will depend on the degree of neurological involvement. Pain killers are recommended for back pain. Relaxation techniques, and transcutaneous electric nerve stimulation may also be helpful in relieving pain. For spinal cord tethering, surgery may be suggested.

Those with occulta spinal dysraphism with associated cord anomalies often have skin abnormalities with or without neurological symptoms. An MRI should be obtained to assess the level of termination of spinal cord. Decision for neuraxial anesthesia should be based on this [9]. Regular observation of the child during growth and development is very important and patients should be taught about the same. They should be urged to report neurologic symptoms, if any. It is still not clear whether folic acid dose of 0.4 mg should be recommended in women who had a child affected by spina bifida occulta [10].

Prognosis

In general, spina bifida occulta does not cause neurological dysfunction, except for mild manifestations like foot weakness or bowel and bladder disturbances. Prognosis of this condition is very good and many patients are able to carry on with a normal life.

Etiology

Multiple factors including genetic, environmental, and racial factors are implicated in the development of spina bifida occulta. In addition, cytoplasmic factors, polygenic inheritance, and chromosomal aberrations are also considered to be etiological factors of this condition. Lack of folic acid in mother’s diet during pregnancy increases the risk of this disease [3].
Abnormalities in secondary neurulation is considered to be one of the most common causes of spinal bifida occulta. This includes diastematomyelia, diplomyelia, dorsal dermal sinus, spinal lipoma and also fusion defect in dorsal spinal column. All these are covered or fully epithelialized, thus hiding the defects in the neural tissue or meninges. The skin covering the defect may be dysplastic. The mildest form of this condition is caused by the failure of the spinal arch to fuse completely. This is not associated with any abnormalities of the spinal cord or nerve roots. Bodies of several vertebrae are fused together in most severe form of spinal bifida occulta. This results in a short and stiff back.

Epidemiology

Actual incidence of spina bifida occulta in the general population is not known. Detection rate of this hidden spinal bifida has increased in the recent years due to improved imaging techniques [4]. In general, incidence of spinal bifida is higher in British isles, while it is low in southern China and Japan. The incidence is found to be two times greater in North and South Carolina, when compared to other parts of United States. Low socioeconomic status is found to be associated with higher risk of neural defects. Prevalence of spinal bifida is found to be greater among white and Hispanic people [5]. Spina bifida occulta has a decreased incidence among older patients [6]. Posterior disc herniation at L4-5 or L5-S1 were found in 82% of the patients with this condition. In young patients with spinal bifida occulta, lumbar disc degeneration had a higher incidence. About 54% of these patients had lumbar disease at L3-4, L4-5 or L5-S1 [7]. In about 60% of the cases, neural damage is noted in L4 and S2 levels.

Sex distribution
Age distribution

Pathophysiology

Spina bifida occulta is characterized by the failure of fusion of posterior vertebral laminae. This affects the differentiation of the neural tube that often happens between 17th and 30th day of gestation. Spina bifida occulta does not result in serious neurological abnormalities. Clinical manifestations are seen during rapid growth due to tethering of spinal cord. Incomplete closure of one or more vertebrae, without protrusion of meninges or spinal cord, are characteristic of spina bifida occulta. This often leads to skin deformities, particularly above the region of spinal defect. A small depression with a tuft of hair or soft fatty deposits can be noted above the defect.

Prevention

As the etiology of this condition is still not known, preventive measures remain unknown. Avoiding exposure to radiations during pregnancy is considered to be a good measure. Having folic acid during pregnancy may also be helpful in preventing the development of the condition. Females of childbearing age should be encouraged to take folic acid supplementation every day for having healthy children.

Summary

Spina bifida occulta is a form of spina bifida, in which the neural defect is hidden completely under the skin. Telltale signs of the defect can be seen in some patients on close observation. These defects may be mesodermal, neural or ectodermal in origin [1]. It is considered to be the most common form of spinal bifida, and about 10 to 20% of otherwise healthy people is thought to have this mild form of neural defect. It may affect any level of the spine, but is more common in the lower part. It is usually diagnosed as an incidental finding on an X-ray, and occasionally in MRI. This condition may be associated with chronic back issues, enuresis, and also different types of neurological problems [2].

Patient Information

Spina bifida occulta, or hidden spina bifida, is a condition in which skin covers a spinal deformity. The deformity may be present in any part of the spine, but is usually seen in the lower part of the back. In this condition, the vertebrae fail to fuse completely and remain split at one part. In most of the patients, only one vertebra is involved in the condition and hence may be insignificant with mild manifestations. But occasionally, the split may be large, or two or more vertebrae may be involved. In all these cases, the defect is covered by skin on the top and hence not visible on physical examination.

Spina bifida occulta results from a defect in the development of the spinal cord. The actual cause of the condition is not known, and several genetic and environmental factors are implicated in its development. Lack of folic acid in the diet of a pregnant women is also considered to be one of the causes of the disease. In general, this condition does not result in any neurological dysfunction, but may cause bladder or bowel disturbances, or weakness in foot. In severe form of this condition, two or more vertebrae may be involved and the person’s back may be short and stiff. Pain and stiffness of the back are the two common symptoms of the condition. There may or may not be any visible signs at the back on physical examination. When present, skin above the spinal defect may show a depression. A tuft of hair may grow from this depression. Other symptoms include:

  • Back pain
  • Weakness in the legs
  • Numbness in the legs
  • Deformity in legs, feet or back
  • Change in the functioning of bladder or bowel like incontinence
  • Loss of reflex

Fat patches can be noted over the region at the base of the spine in some cases. Most of the symptoms may be present at birth, but some may develop later in life. This condition is considered to be existing in over 25% of the general population, usually remaining asymptomatic. In many cases, spina bifida occulta is incidentally found during an X-ray performed for some other condition or back pain. MRI is also helpful in assessing the extent of deformity in the bone. It also helps to evaluate the soft tissue damage within the region of deformity. Spina bifida occulta has its onset early in pregnancy. Amniocentesis and fetal ultrasonography are considered to be the two diagnostic tests useful in detecting the neural abnormality. Maternal blood levels of alpha fetoprotein is used in assessing the presence of possible neural defects. Postnatal physical examination, presence of neurologic symptoms, visual spine examination, are all diagnostic procedures for detecting the presence of this abnormality.

This condition does not require any specific treatment. But one should be careful enough to monitor the child through his/her growth and development. If neurologic symptoms develop at a later stage, intervention may be needed. In most of the cases, patients will be able to live their life normally. Since the actual cause of the disease is not clear, no preventive measures are known. Having folic acid supplement during pregnancy is considered to be helpful in preventing the condition. In general, spina bifida occulta has a good prognosis. Back pain, the most common symptom, is controlled with the help of pain medications.

References

Article

  1. Frank JD, Fixen JA. Spina bifida. Br J Hosp Med. 1980;24:422-437. 
  2. Avrahami E, Frishman E, Fridman Z, Azor M. Spina bifida occulta of S1 is not an innocent finding. Spine. 1994;19:12-15. 
  3. Farine D, Jackson U, Portale A, et al. Pregnancy complicated by maternal spinal bifida. A report of two cases. J Reprod Med. 1988;33:323-326.
  4. Carter Co, Evans KA, Till K. Spinal dysraphism: genetic relation to neural tube malformations. J Met Genet. 1976;13:343-350.
  5. Canfield MA, Marengo L, Ramadhani TA, Suarez L, Brender JD, Scheuerle A. The prevalence and predictors of anencephaly and spina bifida in Texas. Paediatr Perinat Epidemiol. 2009;23(1):41-50.
  6. Sutow WW, Pryde AW. Incidence of spina bifida occulta in relation to age. AMA J Dis Child1956;91:211-217. 
  7. De Bakker HM, Roos RA, Voormoolen JH, Vielvoye GJ. Lumbar disc regeneration in spinal dysraphism. AJNR AM J Neuroradiol. 1990;11:415. 
  8. Iskandar BJ, Oakes WJ. Occult spinal dyspharism. In: Albright AL, Pollack AF, Adelson PD, eds Principles and practice of pediatric neurosurgery. Newyork: Thieme; 1999.
  9. Tidmarsh MD, May AE. Epidural anaesthesia and neural tube defects. Int J obstet Anesth1998;7:111-114.
  10. Rizk E, Iskandar JB. The role of folate supplementation in spinal bifida occulta. In Yamadai S ed. Tethered cord syndrome in children and adults. Park Ridge, IL: American Association of Neurological Surgeons; 1996:142-145.

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Last updated: 2018-06-22 03:27