Spinal dysraphism is a very general term for congenital anomalies resulting from incomplete or aberrant neural tube fusion. In a spinal dysraphism, there is often an abnormal fusion of the midline embryonic neural, vertebral and mesenchymal structures. Spinal dysraphism results from an event very early in an embryo’s development.
Types of spinal dysraphism include myelomeningocele, spina bifida occulta, spinal cord malformation, spinal cord lipoma, dermal sinus tract, tight filum terminale and tethered spinal cord. A person with spinal dysraphism may have more than one type. The causes of spinal dysraphism involve both genetic and environmental ones.
The estimated incidence of spinal dysraphism is about 1-3 per 1000 live births.
This class of disorders has several types. The forms of spinal dysraphism include:
- Spina bifida: Spinal bifida is a general term for malformations where the neural tube does not close completely and the lowest portion of the spine. It has three types: spina bifida occulta, meningocele and myelomeningocele.
- Spina bifida occulta: It is the most subtle and minor form of spina bifida. Spina bifida occulta only results in a slight malformation of the back part of the vertebra but the spinal cord and its membranes are not affected.
- Meningocele: This is a more severe form of dysraphism. The spinal cord is generally normal but the overlying coverings of the spinal cord develop abnormally.
- Myelomeningocele: It is the most severe form of spina bifida. In myelomeningocele, the spinal cord and its membranes are not contained within the spinal column but protrude into a sac outside the body.
- Spinal cord malformation (also called “Diastematomyelia”): This form of spinal dysraphism results in a spinal cord which is split down the middle, usually in the lower back, into two “hemi-cords”.
- Spinal dermal sinus: This is an abnormal connection between the skin and the deeper structures of the spine which can cause infection or other problems if it involves the spinal canal.
- Spinal lipoma (also called “Lipomyelomeningocele”): Abnormal development of fat cells will lead to a fatty mass (lipoma) in the spine which can involve the spinal cord itself.
- Tethered cord: A tethered cord is a spinal cord which is tethered, or stuck, down toward the tail end of the spine and does not move up appropriately during development and growth. It occurs primarily because of the abnormalities in the development at the end of the spinal cord, such as a thickened filum terminale.
What causes spinal dysraphism is not yet understood. However, according to the previous study, generic and environmental factors appear to play a role in it. The spinal cord develops very early in fetal development in the first several weeks of gestation and many abnormalities generally occur during this time when the nervous system is first developing.
Therefore, patients commonly are born with spinal dysraphism. Besides, robust maternal nutrition early in pregnancy, such as adequate levels of a vitamin called folate, seems to protect against some forms of spinal dysraphism.
The symptoms of spinal dysraphism can vary tremendously. Some subtle abnormalities may not cause obvious symptom and are often left unnoticed while others can have severe, debilitating effects on the neurological functioning of the lower extremities and lead to considerable dysfunction.
In the most severe malformations, such as significant meningocele and myelomeningocele, there is a large bulging sac hanging out of the back. Possible symptoms may include:
- Severe pain in the back that radiates to the legs, groin, and perineum
- Bowel control problems
- Mobility and sensory deficit in lower limbs
- Urinary incontinence or retention
- Progressive neuropathic bladder
- Poor voluntary control
- Renal stones or renal failure
The diagnosis of spinal dysraphism can be done during pregnancy as well as after birth. Typically, diagnosis procedures include:
- Plain X-rays
X-rays can reveal skull defects, spine deformities, and bony anomalies.
is the most useful diagnostic tool for diastematomyelia or tethered cord. MRI
is the investigation of choice to study the neural tissue abnormalities and
assess the severity of hydrocephalus and Chiari malformation. It is also
considered to be the gold standard for diagnosing a tethered cord.
It can be used to obtain to assess hydrocephalus, a tethered cord in children under the age of 6. A tethered cord is often diagnosed as a “low conus.”
for spinal dysraphism is mostly surgical but it varies depending on the type
and severity of the malformation.
For myelomeningocele, the surgeon operates a surgery to remove problematic elements, restore the normal structure, and then close the membranes and skin over the spinal cord. This operation cannot reverse the damage but it prevents further damage and reduces the risk of infection.
For spina bifida occulta, it does not require surgical repair if it causes no symptoms.
For diastematomyelia, the most common surgery is called decompression surgery, which involves removing the thin piece of bone or cartilage that divides the spinal cord. It will provide more room for the spinal cord within the spinal column. Sometimes the dura is also repaired by the surgery.
For lipomyelomeningocele, it is treated by freeing the spinal cord from its attachment to the lipoma, removing as much of the lipoma as safely possible, and closing the membranes over the spinal cord.
For tumors and cysts, they
may be removed from the spinal cord with microsurgical resection. This type of
surgery uses an operating microscope and very fine tools to remove the masses.
For a tethered cord, surgery
is tailored to its cause. In general, the spinal column is opened from behind through
a laminectomy to reveal the location of the tether.
Each patient should consult their own treating physicians to decide the management options that apply to their personal condition.
Keywords: spinal dysraphism.