What is Partial Spina Bifida (Spina Bifida Occulta)
Partial spina bifida, also known as spina bifida occulta, is a closed neural tube defect where the vertebral arches fail to close completely over the spinal cord, but unlike open spina bifida, the defect is covered by skin and typically does not expose neural tissue. 1
Definition and Pathophysiology
Spina bifida occulta represents the mildest form of spinal dysraphism, occurring when the neural tube fails to close properly during the first 28 days after conception, specifically affecting the lumbosacral region most commonly. 2, 3 Unlike myelomeningocele (open spina bifida), which results from failure of primary neurulation with exposed neural tissue, spina bifida occulta is a "closed" neural tube defect that is skin-covered and often asymptomatic. 3, 4
The key distinguishing feature is that the bony defect lacks complete vertebral arch closure but the overlying soft tissues and skin remain intact, concealing the underlying abnormality. 5
Clinical Spectrum
The condition exists on a spectrum:
- Asymptomatic spina bifida occulta: Simple bony defect with no associated spinal cord abnormalities, often discovered incidentally 3
- Occult spinal dysraphism with complications: May include tethered cord syndrome, intraspinal lipomas, or other structural abnormalities that can cause progressive neurological deficits 1, 6
Critical Clinical Implications
While often benign, partial spina bifida requires vigilance for several reasons:
- Tethered cord syndrome risk: All patients require continued lifelong surveillance for development of tethered cord syndrome, which can cause progressive neurological deterioration 1, 6
- Urological complications: Bladder dysfunction can develop insidiously, leading to chronic kidney disease and renal failure (affecting approximately 26% of patients), representing a serious source of morbidity and mortality 1, 6
- Bowel dysfunction: Can significantly impact quality of life and requires proactive management 1
Essential Diagnostic Approach
MRI is the gold standard for characterizing intraspinal abnormalities and ruling out tethered cord syndrome, particularly when bowel/bladder dysfunction or lower limb upper motor neuron signs are present. 1
- Renal and bladder ultrasound should be obtained within 1 week if diagnosed in infancy 1
- Regular urodynamic testing (videourodynamics or cystometrogram with voiding cystourethrogram) is recommended to detect bladder dysfunction before upper tract changes develop 1, 6
Prevention Context
The same folic acid supplementation that prevents open neural tube defects also reduces risk of spina bifida occulta, as all forms of spina bifida result from neural tube closure failure during the same critical 28-day window after conception. 2, 7 Women of reproductive age should consume 400 μg (0.4 mg) of folic acid daily, with supplementation ideally starting at least 1 month before conception. 1, 7