Tethered Spinal Cord
Tethered = fastened or tied down
Cord = the spinal cord, a bundle of nerves that connects brain and body
Tethered cord is an umbrella term for several different conditions. The common factor in all tethered cord conditions is that the spinal cord’s movement is restricted at its base. Therefore, during everyday activities, the spinal cord cannot move up and down inside the spinal canal. Instead, it pulls against the restriction. In some cases this pull on the spinal cord is minimal and unlikely to cause damage. In more severe cases, the pressure can permanently injure the delicate tissues of the spinal cord.
Tethered cord may be congenital (present at birth, a result of developmental malformation) or it may be acquired (arise later in life). Congenital tethering is usually discovered in childhood, but not always. In some cases congenital tethering is not discovered, or not diagnosed correctly, until adulthood. Diagnosis of congenital or acquired tethered cord is relatively rare in adults.
In adults, symptoms of tethered cord often develop slowly, but they can become quite severe. Symptoms may include back pain that radiates to the legs, hips, and the genital or rectal areas. The legs may feel numb or weak, and may lose muscle. Bladder and bowel control may be difficult.
Back pain from tethered cord is often aggravated by bending slightly forward, by sitting upright with crossed legs, or by holding a moderate weight (such as a baby or a stack of books) at waist level. This pattern of pain is sometimes called the “3-B sign” for bending, Buddha-sitting, and baby-holding.
Adult tethered cord is rare. Red flags that might lead a doctor to suspect tethered cord include any of its symptoms (although the same symptoms can be caused by a number of other spinal cord conditions); a previous diagnosis of a congenital spinal malformation; a history of cancer, infection, spine surgery; or spinal cord injury.
A doctor may test a patient’s muscle strength or ask the patient to move in different ways. A patient may receive magnetic resonance (MR) or computed tomography (CT) imaging, or ultrasound.
Once tethered cord is diagnosed, the surgeons at the Spine Hospital at the Neurological Institute of New York may run a few additional tests. Tethered cord conditions may cause syrinxes, or fluid-filled cysts, elsewhere in the spinal cord. The pressure exerted by a syrinx can also damage the spinal cord. For this reason it is a good idea to scan the entire spinal cord, and potentially the brain, prior to treatment.
Tethered cord can occur due to other congenital defects of the spine. The various congenital causes include:
- Tight filum terminale, in which the delicate strand of supporting tissue at the base of the spinal cord is thickened
- Lipomeningomyelocele, in which a growth of fatty tissue becomes entangled with the spinal cord and nerve roots
- Split cord malformation, in which part of the spinal cord is split lengthwise
- Dermal sinus tract, in which an abnormal channel may lead from the skin to the spinal cord or its coverings
- Dermoids, or benign growths, of the spinal cord
- Myelocystocele, a type of closed spina bifida in which a cyst forms at the base of the spinal canal
Tethered cord can also arise in a previously normal spine. Possible causes of a tether in a previously normal spine include:
- A spinal tumor
- Scar tissue (from surgery or an injury) that binds to the spinal cord
The neurosurgeons at the Spine Hospital at the Neurological Institute of New York believe that surgery may not be needed for every adult with tethered cord. In adult patients with no symptoms or minimal symptoms, careful observation may be an appropriate course of action.
When surgery is the best choice, our surgeons tailor the operation to the cause of the tether.
In general, for any type of tether surgery, the bones of the spinal column are opened from behind to expose the full extent of the spinal cord tethering. The cause of the tether is identified, carefully isolated and released to relieve any further tension on the spinal cord. Our doctors often work collaboratively with neurophysiologists to monitor spinal cord and nerve function during the delicate operations. This precise monitoring can help minimize risk to the spinal cord, nerves, and nerve roots.
The great majority of patients do well with surgery. Most stabilize or even improve their level of function. The spinal cord does have the potential to re-tether after surgery, though. For this reason, follow-up care is important after tethered cord surgery.