What is Spina bifida?
Neural tube defects
The neural tube is the structure in an embryo from which the brain and spine are formed. The neural tube normally closes spontaneously. If spontaneous closure does not occur, a neural tube defect results.
There are 3 major neural tube defects (NTDs) – spina bifida, encephalocele and anencephaly. This guidance covers only spina bifida.
Spina bifida
This is the most common NTD in which there is abnormal development of the coverings of the spinal cord. There are several varieties of spina bifida.
Spina bifida aperta (open neural tube defect)
Myeloschisis / Rascischisis
This is malformation of the spinal cord with no normal spinal cord development below the lesion and no normal covering of the neural structures. This is a very significant abnormality akin to a complete spinal cord injury with abnormalities of bladder, bowel and lower limb function. Some will have hydrocephalus and associated congenital brain abnormalities.
Open myelomeningocele
The spinal cord is open to the surface (placode) but has some normal anatomical appearances below the lesion. However, in the majority of these lesions there is very poor function below the level of the lesion. As for Myeloschisis / Rascischisis there is an association with hydrocephalus and congenital abnormalities of the brain.
Dermal sinus tract
There is abnormal preservation of a tubular connection of skin tissue onto or into the spinal cord. They are commonly associated with dermoid cysts ( a sac like growth that contains structures such as hair, fluid, teeth, or skin glands that can be found on or in the skin) and can result in severe inflammatory damage to the spinal cord and infection similar to meningitis. Spinal cord function may be normal but has the potential for late deterioration at any time in life.
Spina bifida occulta (closed neural tube defect)
Closed meningomyelocele
This is like an open myelomeningocele but in a closed meningomyelocele the skin is closed over the surface.
Meningocele
There is a cystic appearance on the surface of the spine with no spinal cord material in it, due to a cyst of the membranes lining the spinal cord and a defect in the coverings (bone, muscle and skin). Spinal cord function is usually minimally affected. These can have both normal skin cover and no skin cover. They can both result in tethered cord syndrome, as can any of the spina bifida abnormalities.
Lipomyelomeningocele
There is usually a connection of fatty material, blending into the subcutaneous fat through a defect in the dura (membrane covering the spinal cord), bone and muscle, attached to the spinal cord. Spinal cord function can vary from normal through to complete lack of function below the lesion.
Diastematomyelia
There is a defect of the failure of the spinal canal to develop correctly with two canals and the cord split, usually asymmetrically, by a bone or cartilaginous spur or merely a dural fold. This tethers the cord causing traction injury that may be asymmetrical.
Fatty filum terminale
There is abnormal fatty thickening and shortening of the filum terminale (a long slender strand of connective tissue extending from the end of the spinal cord to the termination of the spinal canal) that causes traction on the spinal cord that causes tethered cord syndrome. People with this may have normal function or have subtle abnormalities such as leg or back pain.
Anterior sacral meningocele
There is dysraphism (defective closure of the neural tube) anteriorly in the sacrum with a significant defect causing mass effect on pelvic structures. When associated with a scimitar shaped sacrum and anorectal abnormalities, it is called Currarino triad.
There are many mixed up versions of these abnormalities that can cause all manner of problems.
Tethered cord syndrome
Traction injury to the spinal cord, which is usually subtle and long standing in onset, with possible abnormalities in bladder, bowel and renal tract, lower limb defects (leg length inequality, club foot, dislocated hip) and scoliosis, in addition to pain in the back and/or legs.
At least 50% of people with an anorectal abnormality have a tethered cord problem too. The majority of people with spina bifida have an additional congenital abnormality. Most will need significant surgical input over many years.
