Spina Bifida Occulta
Spina bifida occulta is a mild and often hidden form of spina bifida in which one or more vertebrae do not completely close around the spinal canal during fetal development. Unlike more severe forms of spina bifida, the spinal cord and its protective membranes remain in their normal position, and the skin over the spine is usually intact. Spina bifida occulta is extremely common and is most often discovered incidentally on imaging performed for unrelated reasons.
What is it?
During fetal development, the bony arches at the back of each vertebra normally grow together and fuse to surround and protect the spinal canal.
In spina bifida occulta, this fusion remains incomplete in one or more vertebrae, leaving a small gap in the bony covering of the spine.
The term “occulta” means hidden, reflecting the fact that this condition is usually subtle and often causes no symptoms.
Unlike more severe forms of spina bifida, the spinal cord and surrounding membranes remain inside the spinal canal, and the skin covering the spine remains closed.
Spina bifida occulta most commonly affects the lower lumbar spine or sacrum, especially the L5 or S1 vertebral levels.
It is one of the most common incidental findings on lower spine X-rays and is often discovered during imaging performed for unrelated back pain or injury.
The exact cause is not completely understood but is believed to involve a combination of genetic and environmental factors during early pregnancy, including folic acid availability.
Most people with spina bifida occulta never know they have it because it usually causes no symptoms or limitations.
Some individuals may have subtle skin findings directly over the affected spinal level, such as a small dimple, patch of hair, birthmark, fatty lump, or pigmented area.
While these findings are often harmless, certain skin markers—particularly in infants and children—can occasionally indicate an underlying spinal abnormality requiring further evaluation.
In a small number of cases, spina bifida occulta may occur alongside conditions such as tethered spinal cord, spinal lipoma, dermal sinus tract, or other forms of occult spinal dysraphism.
These associated conditions may produce neurological, orthopedic, or urological symptoms.
X-rays often identify the bony defect incidentally.
When concerning symptoms or associated abnormalities are suspected, MRI of the spine is the preferred imaging test because it provides highly detailed views of the spinal cord, nerve roots, surrounding tissues, and any tethering abnormalities.
In very young infants, spinal ultrasound may be useful before the spinal bones fully ossify.
Important to Know
For the vast majority of people, spina bifida occulta is a harmless incidental finding that requires no treatment or activity restrictions.
When it is identified during evaluation for back pain, the pain is usually caused by another condition such as muscular strain, degenerative changes, or disc-related disease rather than the bony defect itself.
The main reason additional evaluation may be recommended is to exclude associated spinal cord abnormalities when concerning symptoms or skin findings are present.
Patients with tethered cord syndrome or related abnormalities may develop progressive neurological symptoms over time and sometimes require neurosurgical evaluation.
MRI findings are always interpreted together with the neurological examination, symptoms, and physical findings.
Care may involve pediatric neurology, neurosurgery, orthopedics, or urology specialists when associated spinal dysraphism is suspected.
Red flag symptoms include progressive leg weakness or numbness, gait or balance difficulty, new bowel or bladder dysfunction, recurrent urinary tract infections, foot deformities, or significant skin findings over the lower spine in a child. These symptoms warrant medical evaluation because they may indicate an associated spinal cord abnormality rather than simple isolated spina bifida occulta.