Types of spina bifida

You may not know, but there are a number of different types of spina bifida.  We’ve listed them here along with an explanation of what each one means.

Spina bifida is present from birth and can take several forms.  These are:

Open spina bifida (spina bifida cystica - cyst like)

Closed spinal lesions

Open spina bifida (spina bifida cystica - cyst-like)

The visible signs are a sac or cyst, rather like a large blister on the back.

There are two forms:

Myelomeningocele (meningomyelocele)

Myelomeningocele is the most serious and more common of the two forms of cystic spina bifida. Here the cyst not only contains tissue and cerebrospinal fluid (CSF) but also nerves and part of the spinal cord. The exposed spinal cord is damaged by the fluid in the womb during pregnancy and may also not develop properly. As a result, there is nearly always some resulting paralysis and loss of sensation. Nerves to and from the spinal cord emerging below the damaged region may not pass messages to the brain. The extent of this can be patchy and difficult to predict.

The lower on the spine, and smaller the lesion, the less severe the resulting impairments are likely to be. Bladder and bowel problems occur in most people with myelomeningocele, as the nerves come from the very bottom of the spinal cord, and are always below the lesion. It is also necessary to have intact nerve pathways to the brain for complete control and sensation.


In this form, the sac contains meninges (tissues which cover the brain and spinal cord) and CSF, but no spinal tissue. Development of the spinal cord may be affected, but impairment is usually less severe than myelomeningocele. Meningocele is the least common form of spina bifida.

Closed forms of spina bifida. 

Closed forms of spina bifida are covered by skin at birth, unlike myelomeningocoele or meningocoele, which are exposed and cystic.  

In Spina bifida occulta, one or more of the vertebrae (spinal bones) are not closed completely at the back. Occult spinal dysraphism describes a skin-covered spina bifida, which can include: lipomyelomeningocoele, tethered cord, diastematomyelia or similar. It is helpful to make a distinction between these different conditions, as they can present different challenges and need different treatment approaches. 

Spina bifida occulta 

Spina bifida occulta (SBO) occurs very commonly, affecting an estimated 8-15% of adults. In the UK, this means between 5-10 million people may have one or more vertebrae incompletely closed. In children, this finding is even more common. The vertebrae close later in some children than others until bone growth is complete, by around age 16-18. One study found an open vertebra in 41% of children, so this may be considered a variation rather than a condition, with closure of the vertebral arch completing in some children later than others. Most people will remain unaware of it, or it may be discovered as a chance finding during tests for unrelated conditions, or after accidents. If this describes your situation, please don’t worry.  

MRI scans are much more common these days, and the chances of SBO being identified in people without symptoms are much greater than in previous times. This can cause great anxiety, especially if you have no symptoms, but ask your GP what the MRI report says, and if there are any other differences noted. Don’t stop or restrict your usual activities and keep moving and exercising. Unless your SBO is complicated by other conditions or you are experiencing symptoms, you do not need to do anything differently and you do not need further investigations or treatment. 

SBO can occur anywhere on the spine but is most common where the spine joins the pelvis, at L5/S1. Some people with SBO may have other conditions of the spinal bones, which may (but not always) cause pain and occasionally, nerve involvement, as the spine becomes less stable. These include: 

  • Pars Defect – (a small hairline fracture of part of the vertebrae) Spondylosis - (arthritis of the spine) 
  • Spondylolisthesis - (where one of the vertebrae slip out of position) or click here for more information 

For some people, the identification of SBO may be made during investigation into low back pain. Ask if there are any other features, such as Pars defect, or spondylolisthesis, as these can cause pain. Spondylolisthesis can also compress some of the nerves of the lower spine, so some people may develop pain or muscle weakness in their legs, or bladder and bowel issues. 

Closed spinal dysraphisms (Closed spina bifida, skin-covered spina bifida) 

For some people, there are associated conditions which can have a significant impact on their lives and abilities. The term ‘spina bifida occulta’ is sometimes used to refer to other skin covered lesions (such as lipomyelomeningocoele or diastematomyelia - see below) but it is more accurate and clinically useful to distinguish between those conditions, and uncomplicated gaps in the vertebrae. 

For some people with closed spina bifida, the condition involves the nerves and spinal cord, not only the vertebrae. It may be associated with a fatty lump embedded in the spinal column (lipomyelomeningocoele), or a piece of bone which divides the spinal cord (diastematomyelia). 

There may be visible signs on the back such as a lump, a haemangioma or naevus (strawberry birthmark), a tuft of hair (similar to head hair, rather than downy back hair) or a deep dimple or sinus (hole) above the cleft of the buttocks. Small shallow dimples in the cleft of the buttocks are very common and tend not to be associated with closed spina bifida. 

The effects and complications of spina bifida occulta are caused by nerves and spinal tissue being trapped, caught up on abnormal pieces of bone, or tangled in fatty lumps, which prevent the spine moving freely inside the spinal column (see our information on tethered cord).

However, because the lesion is covered in skin, the spinal cord is protected from the damaging effects of the fluid in the womb experienced in myelomeningocele (open spina bifida). Effects may, very occasionally, be present from birth, but more commonly come on during times of rapid growth in childhood, or during middle age.

They can include:

  •      Back pain
  •      Turning in of the feet (Talipes)
  •      ‘Growing pains’, pain, weakness or fatigue during walking
  •      Cramp or pins and needles in the feet and legs
  •      Thinning of the calf muscles
  •      Numbness or lack of sensation on the skin to the feet
  •      Bladder and/or bowel problems.


Lipomyelomeningocoele is a closed spinal lesion in which part of the spinal cord and nerves are tangled in a benign fatty tumour. Like other forms of spina bifida, it develops during early pregnancy. The exact cause is still uncertain, but it is thought that a layer of cells (which will develop into the skin) detaches from the neural tissue too early, allowing fat cells to become attached to the spinal cord, where they grow to form a lump. These fat cells prevent the spinal bones closing completely, leaving the ‘spina bifida’ gap. It is present from birth and is often seen as a skin covered lump on the baby’s back at birth. Around 90% of people with lipomyelomeningocoele have markers on their back such as fatty lumps, birthmarks or deep dimples.

Lipomyelomeningocoele accounts for around 15% of cases of spina bifida. It is usually not detected at the antenatal mid-term ultrasound scan. In open spina bifida, the appearance of the skull bones and cerebellum - part of the back of the brain - show distinct signs to lead the sonographer to look for tiny changes in the spine.

For example, the bones to the sides of the head can look pinched, and the cerebellum looks long, thin and wrapped around the spinal cord, instead of being round (Chiari II). In lipomyelomeningocoele, the brain and skull will usually look normal so the changes to the spine may not be detected.

As lipomyelomeningocoele is skin covered, no ‘back closure’ surgery is needed at birth. It also differs from open spina bifida as it is usually not associated with brain development problems such as Chiari II, so learning and general development should also follow typical patterns. Around 5% of people with lipomyelomeningocoele have aqueduct stenosis (blockage cause by narrowing) which can lead to hydrocephalus.

Problems associated with lipomyelomeningocoele are caused by the spinal cord and nerves being trapped within the fatty lump, and the lump putting pressure on the spinal nerves. This stops the spinal cord from moving freely inside the spinal bones, and with growth the nerves become stretched and damaged; this is what is meant by ‘tethered cord’. (See Shine’s information on tethered cord.) Problems can also develop if the person gains weight – because the lump is made of fat cells, they become larger with weight gain like other fat cells in the body. Fat cells may also be present at the bottom of the spinal cord (fatty filum terminale).

Lipomyelomeningocoele often affects the bladder and bowel, so difficulty with potty training, frequency or urgency of passing urine, a poor, ‘dribbling’ stream of urine in boys, or urine infections may occur. It is very important that all children with conditions which affect the nerves to their bladders have their bladder function checked regularly by a Urologist. Constipation or frequent soiling may be experienced too, and several options for good management are available, such as washout systems.

Treatment for lipomyelomeningocoele, if needed, is usually by surgery to release the nerves from within the fatty lump, which will be done by a Neurosurgeon.

Neurosurgeons differ in their approaches to surgery; some will operate within the first year of life, others prefer to wait until signs or symptoms begin before operating, as scar tissue from the surgery can cause further tethering, and waiting may result in fewer detethering operations over the person’s lifetime. Sometimes, the nerves are entangled in the fatty lump, and it is not possible to free all the nerves or remove all the fat.

Your neurosurgeon should monitor this regularly, but if you notice any changes, contact your neurosurgeon for an appointment, rather than waiting until the next routine appointment.


This is a condition in which the spinal cord is divided into two (lengthways), usually in the lumbar area. (The spinal cord may join up again, but if it doesn’t, it is referred to as diplomyelia.) Around half of people with diastematomyelia have their spinal cord divided by an extra piece of bone or band of fibrous tissue in the spinal canal. The spinal cord can become tethered because of the extra bone or tissue. Treatment usually involves surgery to remove the bone and to free up the spinal cord (detethering). People without the extra bone only occasionally develop symptoms, if the cord becomes tethered. Diastematomyelia can occur alone, or with lipomyelomeningocoele.

More information and advice

If you suspect that you may have spina bifida occulta and are experiencing a few of the problems described above, ask your GP to arrange to investigate. Depending on the findings, a referral to a neurosurgeon might be appropriate.

Shine’s national and regional staff, area and specialist advisers will give personal advice and support whenever possible.

Related conditions

There are a number of conditions that share features with, or are otherwise closely linked to spina bifida.

 Read more on related conditions

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