Spinal Dysraphism

Spinal dysraphism refers to the congenital abnormalities of the spine and spinal cord.

Different types of spinal dysraphism are designated as “open” or “closed” depending on whether or not the abnormality is covered with skin.

Types of open spinal dysraphism include:

In addition to developmental problems with the layers of the spine, some children with these conditions may develop what is called a “tethered” spinal cord. This means that the spinal cord is not able to “float” freely within the spinal fluid the way it normally should.

Spinal dysraphism is caused by abnormalities that occur during early fetal development. Around the third week of development, the fetus forms a structure called the neural tube, which will eventually extend through the baby’s body and give rise to their nervous system. If the lower section of the neural tube does not close completely, the baby will be born with spinal dysraphism.

The more severe forms of spinal dysraphism are diagnosed early in life. Myelomeningocele, for example, is often diagnosed before birth by ultrasound. It is visible to the naked eye, and can be diagnosed immediately in newborns.

A dermal sinus tract is generally visible as a channel, pit or dimple in the skin directly over the spine. However, the naked eye cannot determine whether the channel reaches the spinal cord, whether it may tether the spinal cord, and whether there are masses in the spinal cord. Only an imaging test like a magnetic resonance (MR) scan can provide these answers. A dermal sinus tract should almost always be evaluated by imaging scan. Prompt diagnosis can improve patient outcomes.

Lipomyelomeningocele can sometimes be diagnosed before birth by ultrasound. It can usually be tentatively diagnosed at birth by a pad of fat beneath the skin over the spine.

Spina bifida occulta, diastematomyelia, and dermoid and epidermoid cysts themselves are not visible to the naked eye, but they sometimes cause visible skin signs: a thick patch of hair, a growth of extra skin, or a difference in skin pigment directly over the defect, for example. When these conditions cause neurological symptoms like scoliosis, leg weakness, pain, or incontinence, they usually do so in the early years of life. Therefore they are usually diagnosed in childhood. Cysts may be found while investigating the spine if they occur along with other forms of dysraphism.

Spinal ultrasound is a common screening study in newborns, but MR (magnetic resonance) imaging is the most useful diagnostic tool for diastematomyelia or tethered cord. MR scans use radio waves and a large magnet to produce detailed images of soft tissues like the spinal cord.

Surgical treatment for spinal dysraphism varies by type.
In myelomeningocele, the defect that exposes the spinal cord to the outside world is repaired in the first days of life. The surgeon protects the spinal cord from further damage, removes as many problematic elements as possible, restores as much normal structure as possible, then closes the membranes and skin over the spinal cord. This operation cannot reverse damage that has already occurred. However, it prevents further damage and dramatically reduces the risk of infection.

The most common surgery for diastematomyelia, calleddecompression surgery, involves removing the thin piece of bone or cartilage that divides the spinal cord. Removing this piece provides more room for the spinal cord within the spinal column. In many cases, removing this piece also “un-tethers” the spinal cord, allowing it to move freely once again. Sometimes the dura, the sleeve around the spinal cord, is also repaired at the time of surgery.

Lipomyelomeningocele 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.

The goals of surgical treatment of dermal sinus tract are to remove the tract, untether the spinal cord, and to prevent any loss (or any further loss) of neurological function. The tract must be removed because it provides a conduit from the spinal canal to the outside world.

Tumors and cysts may be removed from the spinal cord with microsurgical resection. This type of surgery uses an operating microscope and very fine tools to remove masses from the spinal cord.

Surgery for tethered cord is tailored to the cause of the tether. In general, the spinal column is opened from behind via a laminectomy to reveal the location of the tether. The surgeon then works carefully to release the constriction.