Tethered spinal cord syndrome
Tethered spinal cord syndrome is a neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column. The attachments cause an abnormal stretching of the spinal cord. They may occur congenitally at the base of the spinal cord, or they may develop near the site of an injury to the spinal cord.
Tethered spinal cord syndrome is closely associated with spina bifida, and it is estimated that 20 to 50 percent of children with spina bifida defects repaired shortly after birth will require surgery at some point to untether the spinal cord.
The lower tip of the spinal cord is normally located opposite the disc between the first and second lumbar vertebrae in the upper part of the lower back. In people with spina bifida (myelomeningocele), the spinal cord fails to separate from the skin of the back during development, preventing it from ascending normally, so that the spinal cord is low-lying or tethered.
Although the skin is separated and closed at birth, the spinal cord stays in the same location after the closure. As the child continues to grow, the spinal cord can become stretched, causing damage and interfering with its blood supply.
The causes, which vary in severity of symptoms and treatment, include:
- Dermal sinus tract (a rare congenital deformity)
- Diastematomyelia (split spinal cord)
- Lipoma (a benign, fatty growth)
- Thickened/tight filum terminale (a delicate filament near the tailbone)
- Spine trauma
- Spine surgery
- Lesion on the lower back
- Fatty tumor or deep dimple on the lower back
- Skin discoloration on the lower back
- Hairy patch on the lower back
- Back pain, worsened by activity and relieved with rest
- Leg pain, especially in the back of legs
- Leg numbness or tingling
- Changes in leg strength
- Deterioration in gait
- Progressive or repeated muscle contractions
- Leg deformities
- Spine tenderness
- Scoliosis (curvature of the spine)
- Bowel and bladder problems
The course of the disorder is progressive. Tethered spinal cord syndrome may go undiagnosed until adulthood, when pain, sensory and motor problems, and loss of bowel and bladder control emerge. This delayed presentation of symptoms is related to the degree of strain placed on the spinal cord over time and may worsen during sports or pregnancy, or may be due to narrowing of the spinal column (spinal stenosis) [link to spinal stenosis] with age.
Tethering may also develop after spinal cord injury, and scar tissue can block the flow of fluids around the spinal cord. Fluid pressure may cause cysts to form in the spinal cord, a condition called syringomyelia. This can lead to additional loss of movement, feeling or the onset of pain.
If a tethered cord is suspected, one or more tests may be necessary to confirm the diagnosis.
- CT scan
MRI imaging is often used to evaluate the cause of the symptoms, and can be used to diagnose the location of the tethering, lower than normal positron of the conus medullaris or presence of a tumor or fatty mass (lipoma).
Untethering is generally performed only if there are clinical signs or symptoms of deterioration. In children with repaired spina bifida defect, the surgery involves opening the scar from the prior closure down to the covering (dura) over the myelomeningocele. Sometimes a small portion of the bony vertebrae (the laminae) is removed to obtain better exposure or to decompress the spinal cord. The dura is then opened, and the spinal cord and myelomeningocele are gently dissected away from the scarred attachments to the surrounding dura. Once the myelomeningocele is freed from all its scarred attachments, the dura and the wound are closed.
Many children require only one untethering procedure. However, since symptoms of tethering can occur during periods of growth, 10 to 20 percent require repeated surgery.
If surgery is not advisable, spinal cord nerve roots may be cut to relieve pain. In adults, surgery to free the spinal cord can reduce the size and further development of cysts in the cord and may restore some function or alleviate other symptoms. Other treatment is symptomatic and supportive.
With treatment, individuals with tethered spinal cord syndrome have a normal life expectancy. However, some neurological and motor impairments may not be fully correctable. Surgery soon after symptoms appear may improve chances for recovery and can prevent further functional decline.
Source: National Institute of Neurological Disorders and Stroke and American Association of Neurological Surgeons