Tethered cord syndrome (TCS) or occult spinal dysraphism sequence refers to a group of neurological disorders that relate to malformations of the spinal cord. Various forms include:

• Tight filum terminale
• Lipomeningomyelocele
• Split cord malformations (diastematomyelia)
• Dermal sinus tracts
• Dermoids
• Cystoceles.

All forms involve the pulling of the spinal cord at the base of the spinal canal, literally a tethered cord. The spinal cord normally hangs loose in the canal, free to move up and down with growth, and with bending and stretching. A tethered cord, however, is held taut at the end or at some point in the spinal canal. In children, a tethered cord can force the spinal cord to stretch as they grow. In adults the spinal cord stretches in the course of normal activity, usually leading to progressive spinal cord damage if untreated. TCS is often associated with the closure of a spina bifida. It can be congenital, such as in tight filum terminale, or the result of injury later in life.