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As a human embryo develops, the spinal cord starts out as a flat plate of cells on the surface of the embryo. This plate later rolls into a tube and becomes surrounded by a tough covering called the dura, then muscle and bone, which form later in the process. During fetal development, the spine lengthens faster than the spinal cord, so that the lower end of the spinal cord ends up at the level of the second or third vertebrae in the lower back.
If all goes smoothly, the cord grows so it can move up and down freely in a channel within the protective bones of the spine. But sometimes the spinal cord becomes attached, or tethered, to the surrounding tissue, usually at the base of the back. If this happens, the cord will become tight and stretched as the child grows, leading to symptoms of nerve damage, such as weakness or numbness in the legs, back pain, and trouble controlling the bladder or bowels.
If the syndrome is associated with myelodysplasia, it will usually be repaired at the same time as the neural tube defect. It can also be caused by a spinal lipoma (fatty deposit in and around the spinal cord), injury, tumor or (most commonly) by a fatty or tight filum (the filament of tissue that extends from the lower end of the spinal cord). In these cases, a child may not develop symptoms until they hit a growth spurt later in life. Surgery to release the spinal cord and allow it to move freely is the recommended treatment for a tethered cord that is causing symptoms. In fatty or tight filum cases, this surgery is relatively quick and straightforward.
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