Spina Bifida Occulta

Spina Bifida Occulta refers to a group of conditions involving the spinal column - a structure made of bones called vertebrae. The spinal column supports the skeleton and protects the spinal cord, the cable of nervous tissue that transmits information between the brain and the body. Spina Bifida Occulta is a common condition in 10-20% of otherwise healthy people; it is often found incidentally during a radiogram (X-ray) or magnetic resonance imaging (MRI) of the lower back. Spina Bifida Occulta means "hidden split spine." The term is misleading because it is used to describe several conditions.

The most frequently seen form is considered harmless and is simply a variant of normal vertebral (bone) anatomy. In this condition, parts of the spine's bones, the spinous process, and the neural arch appear abnormal on a radiogram. Usually, the spinal cord and spinal nerves are not involved. Isolated bony Spina Bifida Occulta (without an underlying spinal cord abnormality) does not lead to problems with the nervous system. Some radiologists have resorted to calling this situation a vertebral fusion defect, thus removing the reference to Spina Bifida.

However, those (much less common) related conditions, also called Spina Bifida Occulta, that affect the spinal cord are the ones that can have potential health consequences. These conditions include:

These conditions may occur without bony abnormalities of the vertebrae. If any of these associated spinal cord abnormalities occur, signs and symptoms related to the nervous system may occur.

Signs and Symptoms

• Pain (in the back and /or legs)
• Weakness in the legs
• Numbness and/or other changes in sensation in the legs and/or back
• Orthopedic deformities in the legs, feet, and back
• Change in bladder or bowel function

Individuals with a likely underlying spinal cord abnormality should receive prompt medical/surgical evaluation to prevent the neurologic problems listed above. How can individuals who might need this type of evaluation be identified? The appearance of the skin overlying the lower back provides clues as to whether a spinal cord abnormality is likely to be present underneath. About 80% of people with spinal cord abnormalities will have some skin abnormality overlying the defect.

Skin Defects

• Hairy patch
• Fatty lump/dimple above the buttocks
• Hemangioma - a reddened or purplish spot on the skin made up of a collection of blood vessels
• Skin tract (tunnel) or sinus—sometimes noted on the back as a deep dimple - especially if it is too high, i.e., higher than the top of the buttocks crease, or if its bottom cannot be seen
• Hypopigmented spot—an area with decreased skin color
• Birthmarks such as a dark spot or red birthmark

Regardless of age, people with lower back skin abnormalities should seek evaluation by a physician knowledgeable in spinal cord malformations. Not every person with a lower back skin defect has Spina Bifida Occulta, particularly those with sacral dimples. Studies such as ultrasound (only valuable for newborns) or spine MRI may be requested to evaluate the underlying structures.

One final issue regards the inheritance patterns of Spina Bifida Occulta and Spina Bifida. Myelomeningocele (or meningomyelocele), an open form of Spina Bifida (where the spinal cord abnormality is visible through an open skin defect), occurs more often in families who have already experienced this condition.

The risk of recurrence in those who have a first-degree relative (parent, sibling) is 5-10 times greater than that in the general population. The risk of having other forms of Spina Bifida when a case of myelomeningocele has occurred already in the family is probably higher than in the general population. However, the genetic risk of recurrence with symptomatic forms of Spina Bifida Occulta is uncertain. Medical evaluations and genetic/pregnancy counseling should be done on a case-by-case basis with knowledgeable professionals. In all circumstances, all women of childbearing age should consume 0.4 milligrams of folic acid daily.