What is spinal cord tethering?
Spinal cord tethering is an abnormal connection between the spinal cord and other parts of the back including the bone, muscle and connective tissues. This causes the spinal cord to stretch because the bones and other tissues of the spine grow faster than the spinal cord.
A spinal tether can take several forms, some of which are easily treated with surgery and without risk of recurrence. Other forms are quite complex and may require life-long monitoring.
Types of spinal cord tethering
The most common form of spinal cord tethering is fatty filum terminale, also called thickened filum. The filum terminale is normally a thin, flexible fiber that connects the bottom of the spinal cord to the bottom of the bones of the spine. Spinal cord tethering can occur if this fiber is thicker and stronger than normal. In such cases, the filum is typically infiltrated with abnormal fat. As the spine grows, the abnormally thick fiber stretches the spinal cord, like a rubber band.
Lipomyelomeningocele is another more complex form of spinal cord tethering, where an abnormal collection of fatty and fibrous tissue attaches broadly to the spinal cord. This tissue typically extends through the bones of the spine, through the muscle, and connects to these tissues as well as to the skin. Lipomyelomeningoceles can cause recurrent tethering and need life-long monitoring for symptoms. Surgery for lipomyelomeningocele is more complex than surgery for fatty filum terminale.
Several other malformations can cause spinal cord tethering. These include previously repaired spina bifida, splitting of the spinal cord, or cystic dilation of the bottom of the spinal cord. These conditions are much rarer than fatty filum terminale and lipomyelomeningocele.
What causes a tethered spinal cord?
Spinal cord tethering is a developmental abnormality, meaning that it is present before birth. It is caused by a problem with the normal spinal cord formation, such that the spinal cord does not separate from the nearby muscle, bone, fat and skin in the usual fashion.
We do not know what factors cause spinal cord tethering or any pre-natal treatments that prevent it.
Who gets spinal tethering?
Most studies suggest that girls are almost twice as likely as boys to have spinal cord tethering. Some cases of tethered spinal cord are associated with other congenital malformations in the spine, kidneys, digestive system and, less commonly, the heart. These conditions are usually obvious at birth and are a good reason to evaluate children for spinal cord tethering.
Most infants with tethered spinal cord do not have any associated birth defects. Instead, they may have marks on their skin that lead a pediatrician to look for spinal tethering. The most common marks are a dimple over the sacrum or lumbar spine, a birthmark known as a hemangioma, an abnormal collection of fatty tissue beneath the skin, or an abnormally shaped crease in their bottom.
Some children with tethered spinal cord are not identified in infancy. These children will have symptoms related to the bottom of the spinal cord. Common symptoms include back pain, leg pain, constipation, urinary dysfunction (urgency, frequency, accidents or recurrent urinary infections), foot deformities and scoliosis.
Tethering is sporadic and typically does not run in families.