Open Spinal Dysraphism vs. Closed Spina Bifida

When you hear the term “spina bifida,” it is important to know that it is a broad umbrella term for different types of neural tube defects. The fundamental difference between open spinal dysraphism and closed spina bifida is whether the spinal cord is exposed to the outside environment or securely covered by skin ^[1].

Understanding exactly which type your child has is the single most important factor in determining their care path, the specialists they will need, and the urgency of their medical treatments.

Open Spinal Dysraphism (Myelomeningocele)

In open spinal dysraphism, the spinal canal does not close properly, and there is no skin covering the defect ^[1]. The most common form of this is myelomeningocele, where a sac containing the spinal cord and nerves protrudes from the baby’s back.

Because there is no skin protecting the nerves, the spinal cord is exposed to amniotic fluid while the baby is still in the womb ^[2]. This exposure causes “secondary injury”—chemical and mechanical damage to the delicate nerve tissue during pregnancy ^[2][3]. As a result, open spinal dysraphism is typically the most severe form of the condition.

• Symptoms and Severity: Children with open spinal dysraphism often experience nerve damage that can lead to leg weakness, paralysis, or loss of bladder and bowel control ^[4]. It is also frequently linked to structural brain changes, such as hydrocephalus (fluid buildup in the brain) and Chiari II malformation (where the lower part of the brain sits too low in the neck) ^[4][5]. While these symptoms can sound overwhelming, modern medical interventions are actively improving outcomes for many children.
• Diagnosis: These open defects are most commonly detected during a standard 20-week prenatal ultrasound.
• The Care Path: Open spinal dysraphism always requires surgery. In some cases, fetal surgery is performed before birth to cover the exposed nerves and stop the ongoing damage caused by amniotic fluid ^[6][7]. If fetal surgery is not an option, the baby will undergo surgery within the first few days of life to close the opening, protect the spinal cord, and prevent dangerous infections like meningitis ^[8][9]. It is important to know that while surgery stops further damage, it generally cannot reverse the nerve damage that has already occurred ^[6][8].

Closed Spinal Dysraphism: The Spectrum

In closed spinal dysraphism, the neural tissue is safely covered by intact skin or connective tissue ^[1]. Because the spinal cord is enclosed, it is protected from amniotic fluid, meaning babies with closed spina bifida do not suffer the same secondary chemical nerve damage during pregnancy ^[1][2].

However, “closed spina bifida” is a broad category, and the care path depends entirely on how complex the hidden defect is.

Spina Bifida Occulta (The Mildest Form)

The word “occulta” means “hidden,” and this is the most common and mildest form of closed spina bifida. It is typically a simple gap in the spinal bones without any involvement of the spinal cord or nerves ^[10].

• Symptoms: Most people with simple occulta never have symptoms and it is frequently discovered accidentally on an X-ray taken for an unrelated reason ^[10].
• The Care Path: Simple spina bifida occulta usually requires no surgical intervention and is simply monitored ^[11].

Complex Closed Dysraphisms

Some closed defects are more complex and involve the spinal cord itself, despite being covered by skin. For example, a meningocele is a fluid-filled sac covered by skin, and a lipomyelomeningocele involves a fatty lump extending into the spinal canal ^[12].

• Symptoms: Complex closed forms carry a high risk of a complication called tethered cord syndrome ^[13][14]. This occurs when the spinal cord gets stuck to surrounding tissue and stretches as the child grows, which can eventually cause leg weakness, chronic pain, or bladder accidents later in childhood ^[4][15].
• Diagnosis: If a child is born with clues on the skin of their lower back—such as a deep sacral dimple, a patch of hair, or a fatty mass—doctors will use an MRI (the gold standard imaging tool) to see exactly what is happening beneath the skin ^[16][17].
• The Care Path: Unlike simple occulta, these more complex closed defects frequently require surgery to release a tethered cord or remove fatty tissue to prevent progressive nerve damage ^[12][14].

Summary of Differences