What Is Spina Bifida Occulta

Overview

Spina bifida occulta is a common congenital condition that consists in the incomplete closure of the spinal column during early development stages, leading to a small gap or opening in one or most vertebrae (the bones that make up the spine).¹ This opening site is usually very small and covered by a layer of skin, and it can be located in different sites across the spine with varying degrees of severity.² 

It is possible that this lesion may lead to serious neurologic dysfunctions and severely affect the quality of life of the patient, as well as provide a series of limitations whilst growing up. 

As previously stated, this condition occurs during foetal development, typically during the first month of pregnancy, when the neural tube, which eventually forms the spinal cord and brain, doesn't close completely.³

There are four distinct types of spina bifida: occulta, closed neural tube defects, meningocele, and myelomeningocele.² 

• Closed neural tube defects are a diverse group of disorders where the spine may have malformations of fat, bone or meninges (membranes that cover the spinal cord)² 
• Meningocele is a condition that occurs when the meninges protrude through the spine, causing a sac of spinal fluid on the back² 
• Myelomeningocele is the most severe form, where a portion of the spinal cord or nerves are exposed in a sac through an opening in the spinal column²

Unlike other forms of spina bifida, occulta is the most common and mildest form, in which the spinal cord, as well as the nerves that branch out from it, are not exposed or damaged.² It usually is asymptomatic and is often discovered by accident during an x-ray or other similar imaging test.²

Etiology and causes

Generally, spina bifida occurs due to the incomplete closure of the spinal column, typically between the 17th and 30th day of the foetal development.³ Even if the exact cause of these defects is still undetermined², we cannot exclude genetic and environmental influences.³ 

The most common environmental factor linked to spina bifida is folate deficiency. Folate is an essential B-vitamin that we get from the diet, particularly from fruits and vegetables.⁴ Reduced uptake of folate into the system is linked to disrupted cell replication, mutations and disturbed protein formation, all of which can affect spinal growth and correct development.⁴ 

There are now global initiatives through which food is fortified with folate, with the hopes of decreasing the risk of neurological defects.³ 

Other environmental factors include:

• Maternal obesity 
• Maternal diabetes 
• Teratogens (substances known to cause birth defects)³

The genetic factors that also have been correlated with spina bifida, concern genes linked to folate metabolism.² 

Some neural tube development defects are also associated with chromosomal syndromes such as trisomy 13 and 18, meaning there is an additional copy of the given chromosomes.² 

The fact that there is an increased recurrence risk in siblings of affected individuals is yet another evidence that supports the role of genes in the development of this condition.⁴ 

Clinical features

In spina bifida occulta there is no obvious deformity, however there may be a hairy patch or a dimple where the expected spinal defect is located.³ 

On the other hand, there may be some underlying neurological symptoms in spina bifida patients that may include: 

• Pain 
• Movement difficulties 
• Abnormal muscle tightness 
• Cognitive defects
• Seizures³

Most children with a form of spina bifida experience some degree of weakness or paralysis in the lower limbs, and might need support, crutches or, in more severe cases, a wheelchair.¹ 

Other symptoms that may also be presented are: 

• short attention span
• reading difficulties
• difficulty with problem solving
• difficulty with understanding speech
• difficulty in organisation
• struggles with visual and physical coordination and movement¹

Other conditions that can also be induced by the spinal defect are: 

• bowel and bladder incontinence
• endocrine disorder
• developmental issues³
• skin problems and latex allergy¹

Physical symptoms and associated health problems are typically more prominent in the open forms of spina bifida such as meningocele or myelomeningocele, since the nerves would protrude outside of the body.³ However, they can also occur in individuals afflicted with the less serious occulta variant. 

Diagnosis and screening

In most cases, spina bifida is diagnosed before the birth (prenatal diagnosis), however, in some cases, the disorder may go unnoticed.² This eventuality is particularly prominent in mild forms of spina bifida, during which the defect is detected when performing tests for other conditions.² 

The most common prenatal screening methods to identify spina bifida are a maternal serum alpha fetoprotein (MSAFT) screening and a foetal ultrasound.² Another option is an amniocentesis test.²

The MSAFT screen is performed during the second trimester between the 16th and 18th week of pregnancy.^2,5 During this test, the mother’s blood is taken to measure the level of a protein called alpha-fetoprotein (AFP) which is naturally made by the placenta as well as by the foetus.² Abnormally high levels of AFP may indicate that the foetus has spina bifida or another neural tube defect.² 

This test does not confirm the diagnosis and it is not specific for spina bifida, therefore, the clinician may order additional tests.² 

An ultrasound uses high frequency sound waves to create an image of the developing baby.^2,6 It is a very accurate tool for diagnosing certain birth defects during pregnancy, such as spina bifida. This can be performed during the first trimester, between 11 and 14 weeks, or during the second trimester, usually between 18 and 22 weeks.² Generally, the diagnosis is more accurate during the second trimester, since the baby is more developed.² 

Amniocentesis is a more invasive procedure compared to the other prenatal diagnosis tests, as it requires a sample of amniotic fluid surrounding the foetus to be collected for analysis.^2,7 After its collection, the amniotic fluid is tested for specific protein levels that may indicate a neural tube defect or genetic disorders. 

Spina bifida occulta can also be suspected following birth, due to an abnormal fatty mass, clump of hair or a dimple at the site of the defect.² Doctors may also use an ultrasound or x-ray imaging technique to look at the spine if they suspect a defect.² Other tests may include magnetic resonance imaging (MRI) or a computed tomography (CT) scan to get a clearer view of the spinal cord and the surrounding structures.²

Treatment and management

For most people with spina bifida occulta who do not experience complications, no specific treatment is necessary, and they can lead entirely normal lives without any limitations. However, if complications do arise, medical professionals can provide appropriate management, which might include monitoring the condition and, in some cases, surgical intervention.³ 

The main management of spina bifida is prevention, such as supplementing the diet with folate during pregnancy.³ 

There are also symptom-specific approaches, for example the use of laxatives to treat related bowel problems.¹

Prenatal surgery could be recommended in more serious types of spina bifida.² This involves opening the mother’s abdomen and sewing the abnormal opening over the baby’s spine.² Thanks to this intervention, the spinal cord will be covered and, therefore, protected from further damage during foetal development.² 

It has been shown that, when using prenatal surgery as opposed to postnatal, children had better outcomes and less additional symptoms.² 

It should be noted that this sort of surgery presents a wide array of risks and does not restore lost neurological functions, as it only prevents further damage.²

For some forms of open spina bifida, postnatal surgery is required to be performed within the first few days following birth.² It consists in closing the defect to minimise risk of infection or further damage to the exposed nerves.² 

Surgery may also be needed to drain fluid in the brain or improve the alignment of legs and spine.² 

Individuals with spina bifida could also use assistive devices for mobility such as braces, crutches or a wheelchair.² 

Physiotherapy and occupational therapy could also be highly beneficial for individuals to learn how to be as independent as possible.¹ 

FAQs

What is spina bifida occulta?

Spina bifida occulta is the most common and the mildest form of spina bifida, which is a congenital neural tube defect.

Is spina bifida occulta a serious condition?

Spina bifida occulta is usually not a serious condition and often doesn't cause any symptoms or health problems. Many people may not even know they have it because it often goes unnoticed.

What causes spina bifida occulta?

The exact cause of spina bifida occulta is unknown, but it is believed to involve a combination of genetic and environmental factors. 

How is spina bifida occulta diagnosed?

Spina bifida occulta is often diagnosed incidentally when a person undergoes imaging tests for unrelated issues, such as X-rays or MRI scans. 

Can spina bifida occulta be treated?

Treatment for spina bifida occulta is usually not necessary unless it causes symptoms. In such cases, treatment options may include physical therapy, pain management, and in rare cases, surgery to relieve nerve compression.

Summary

Spina bifida occulta is a birth defect that affects the spinal column. It can be characterised by a gap in the spine that in some cases can cause additional neurological effects on the nerve or spinal cords are exposed. There are different types of spina bifida with different ranges of severity, however the occulta variant is the most common and least severe, with the smallest amount of associated symptoms. 

Despite there being clear links between nutritional and genetic risk factors and the development of spina bifida in a baby, more research still needs to be done to determine a clear cause. 

There are many management techniques depending on symptoms and severity, and these include therapy, mobility aid use and surgery. Most individuals with the occulta variant do not have significant complications and can lead perfectly normal lives.