Spina bifida

Spina bifida is a term that is used to refer to a series of birth defects that affect the development of the spine and nervous system.

The neural tube

During the first month of life, an embryo grows in a primitive tissue structure called the neural tube. As the embryo develops, the neural tube begins to change into a more complicated structure of bones, tissue and nerves that will eventually form the spine and nervous system.

In cases of spinal bifida, something goes wrong with the development of the neural tube, and the spinal column (the ridge of bone that surrounds and protects the nerves) does not fully close. Spina bifida is a Latin term that means 'split spine'.

Types of spina bifida

There are three main types of spina bifida:

• Spina bifida occulta.
• Spina bifida meningocele.
• Myelomeningocele.

Spina bifida occulta

Spina bifida occulta is the most common (and least serious) type of spina bifida. In spina bifida occulta, the opening in the spine is very small, with a tiny gap between one or more vertebrae. Vertebrae are the disc-shaped bones that make up your spine.

Spina bifida occulta usually causes no symptoms, and most people will remain unaware that they have the condition. In such cases, no treatment is required.

Spina bifida meningocele

Spina bifida meningocele is the rarest type of spina bifida. In this type of spina bifida, the bones of the spine develop normally, but the protective membranes are pushed out between openings in the vertebrae. These membranes can usually be removed during surgery, and no further treatment is required.

As the nervous system remains undamaged, a person who is born with spina bifida meningocele is unlikely to experience any long-term health problems.

Myelomeningocele

Myelomeningocele is the most serious type of spina bifida. It occurs in an estimated one in every 1,000 births.

In cases of myelomeningocele, the spinal column remains open along several vertebrae, and the membranes and spinal cord push out to create a sac in the baby’s back. The sac can be covered with skin, but it often remains open, leaving the nervous system vulnerable to infections that may be fatal.

In some cases of myelomeningocele, the spinal column can be repaired using surgery. However, extensive damage to the nervous system will have usually taken place already. Damage can result in a range of symptoms including:

• Partial or total paralysis of the lower limbs.
• Learning difficulties.
• Bowel and bladder incontinence.

Around 70% of children with myelomeningocele will also develop hydrocephalus, a condition where there is excess cerebrospinal fluid (CSF). CSF is the fluid that surrounds the brain.

The build-up of CSF is caused by problems with the development of the neural tube. Hydrocephalus needs to be treated with surgery because the extra pressure that is placed on the brain by the fluid can cause brain damage.

Outlook

Advancements in the treatment of spina bifida have resulted in a considerably improved prognosis for the condition.

Before the 1970s, most children with spina bifida would die in their first year of life. But today, an estimated 80% of children survive into adulthood. Although spina bifida can be a challenging condition to live with, many adults with spina bifida lead independent and fulfilling lives.

The rest of this article focuses on myelomeningocele, and this is the type of spina bifida that will be referred to whenever the term ‘spinal bifida’ is used.