The 4 Types of Spina Bifida: Neural Tube Defects Explained

Spina bifida, the term actually refers to a group of birth defects that affect the spinal cord and vertebrae and are caused by incomplete closure of the neural tube during fetal development. No matter the level of severity, all forms of spina bifida have the same basic cause: a neural tube defect that occurs during fetal development. This article discusses the four types of spina bifida and explains what each type entails.

1) Spina bifida occulta

This is the most common and mildest form of spina bifida, where the spinal cord and/or meninges are only slightly protruding through the vertebrae. Often, there are no symptoms and it’s discovered incidentally on an X-ray or MRI. Most people with spina bifida occulta have a normal life expectancy and require no treatment other than monitoring for any neurological changes.

2) Meningocele

Meningocele is the mildest form of spina bifida. It happens when the meninges, the protective covering around the spinal cord, bulge out through an opening in the spine. Usually, only a small portion of the meninges protrude and there’s no damage to the spinal cord. When surgery is needed, it's usually to put the lining back inside the vertebrae or to close off any openings that have developed. The prognosis for meningoceles isn't always good though, as they may develop into other forms of spina bifida or worse symptoms like  syringomyelia (a fluid-filled cavity).

3) Myelomeningocele

Myelomeningocele is the most frequent  and severe type of spina bifida. It occurs when the neural tube doesn’t close properly, resulting in the spinal cord and surrounding nerves being exposed. This can cause a host of problems, including paralysis, incontinence, and hydrocephalus (build-up of fluid in the brain). Surgery is typically required to repair the defect, and many children with myelomeningocele require lifelong care.

4) Arachnoid cyst

Arachnoid cysts are the most common type of spina bifida, accounting for about 50 to 70 percent of all cases. These cysts form when the arachnoid membrane, one of the three meninges that surround and protect the brain and spinal cord, doesn’t close properly during development. Arachnoid cysts can occur anywhere along the spine but are most commonly found in the lower back. 

Arachnoid Cysts account for about 50-70% of all cases. The patient will have a thin, clear fluid filled sac overlying their spinal cord on an MRI or X-ray.