Spinal dysraphism (also called spina bifida) is a condition in which a baby’s spine and spinal cord do not form properly during pregnancy. The spine and spinal cords are then exposed to the surrounding environment inside or outside the body.
Spinal dysraphism is a general term that includes both visible and invisible incomplete formations. In some babies, the incomplete formation is visible on the skin’s surface. In others, the incomplete formation cannot be seen under the skin. Spinal dysraphism affects about 7 out of every 10,000 live births. It is slightly more common in females than males.
What causes spinal dysraphism?
Doctors are still learning about the causes of spinal dysraphism. Spinal dysraphism is not anyone’s fault and it can happen at random. In some cases, spinal dysraphism is hereditary (passed down through families).
What are the different types of spinal dysraphism?
There are 4 types of spinal dysraphism. Each type is listed below from least to most severe.
Spina bifida occulta: When one or more vertebra (bones in the spine) are malformed (not formed correctly), and a layer of skin covers the opening in the vertebrae.
Closed neural tube defects: When the spinal cord has malformations of fat, bone or the meninges (membranes that line the skull and spinal cord).
Meningocele: When spinal fluid and meninges come through an opening in the vertebrae, but the malformation does not contain spinal nerves.
Myelomeningocele: When the spinal cord is exposed through the opening of the spine and contains spinal nerves.
Which medical conditions can go along with spinal dysraphism?
Whether your baby has other medical conditions depends on how severe the spinal dysraphism is and where it is located along the spine. Once your baby is born, they will be closely followed by pediatric specialists who care for various medical conditions.
Medical conditions that can go along with spinal dysraphism include:
Chiari malformation (a condition in which brain tissue extends into the spinal canal, or top of the spinal cord)
Hydrocephalus (a build-up of fluid in the ventricles, or cavities, in the brain
Urinary tract issues (which include trouble emptying their bladder and frequent urinary tract infections
Constipation or stool accidents
Orthopaedic (muscle or bone) problems, such as trouble walking or not being able to walk
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.
However, in rare cases, these conditions are not diagnosed until adulthood. In other rare cases, they are diagnosed in childhood but cause few symptoms and, depending on the age of the child, may not need treatment. Symptoms can progress in adulthood, at which point the conditions may require treatment.
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.
Spina bifida occulta does not need surgical repair if it causes no symptoms.
The most common surgery for diastematomyelia, called decompression 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.