Tethered Cord Syndrome (TCS) is a neurological disorder involving an abnormal attachment of the spinal cord to the surrounding spinal canal. Normally, the spinal cord moves freely within the spinal column, but TCS restricts this natural movement, subjecting the cord to abnormal stretching and tension. This constant mechanical stress can injure the spinal cord and the nerves extending from it, potentially impairing their ability to transmit signals.
Defining Tethered Cord Syndrome
The spinal cord typically ends in the conus medullaris, usually located at or above the first or second lumbar vertebra (L1-L2) in adults. Extending from the conus is the filum terminale, a thin, non-neural fibrous strand that anchors the spinal cord to the tailbone (coccyx). In typical development, the bony spinal column grows faster than the spinal cord, causing the conus medullaris to ascend relative to the vertebrae.
TCS occurs when the spinal cord is held taut, preventing this normal upward movement and stretching the delicate neural tissue. This abnormal fixation can happen at the end of the cord or at any point along the spinal canal. The stretching compromises the blood supply and disrupts nerve cell function, leading to neurological issues. Tethering is classified as primary (occult) when caused by a congenital defect, such as a thickened filum terminale, or secondary when it develops later due to scar tissue or acquired factors.
Causes and Associated Conditions
Tethered Cord Syndrome can arise from congenital malformations present at birth. These causes relate to abnormal neural tube development during fetal growth. The most common congenital cause is spina bifida, particularly myelomeningocele, where the spinal cord fails to separate from the skin. Other congenital issues include a tight filum terminale that is abnormally thickened or shortened, and fatty tumors (lipomas or lipomyelomeningocele) that anchor the cord. Less common causes involve a splitting of the spinal cord (diastematomyelia) or a dermal sinus tract, which is an abnormal channel extending from the skin to the spinal canal.
Acquired tethering typically results from scar tissue formation after previous spinal surgery or trauma. For instance, children who have had surgery to repair spina bifida are at risk for developing scar tissue that reattaches the spinal cord as they grow. Other acquired causes include spinal tumors, infections, or hemorrhage that leads to adhesion formation.
Recognizing the Signs and Diagnostic Tools
The clinical presentation of Tethered Cord Syndrome varies widely depending on the patient’s age. In infants and young children, symptoms often include external signs on the lower back, such as:
- An unusual patch of hair.
- A deep dimple.
- A skin tag.
- A fatty tumor.
They may also show orthopedic issues like foot deformities, difficulty walking, or progressive scoliosis. A sudden change in bladder or bowel control in a toilet-trained child is also a significant indicator.
For adolescents and adults, the primary symptom is often severe lower back pain that may radiate into the legs, groin, or perineum. They may also experience neurological deficits like numbness, tingling, or bilateral muscle weakness in the lower extremities. Bladder dysfunction, such as urinary urgency, incontinence, or difficulty emptying the bladder, is a frequent manifestation of the syndrome. Symptoms often worsen during periods of growth or with physical activity.
The primary tool for diagnosis is Magnetic Resonance Imaging (MRI), which provides detailed images of the spinal cord and surrounding structures. An MRI can confirm a low-lying conus medullaris or identify the underlying cause, such as a lipoma or a thickened filum terminale. Other diagnostic tests include X-rays to assess for bony deformities like scoliosis, and urodynamic testing to evaluate bladder function. Urodynamic studies are particularly helpful, as bladder dysfunction is a sensitive indicator of nerve damage caused by the tethering.
Treatment Approaches and Outcomes
The main goal of treatment for symptomatic TCS is to relieve tension on the spinal cord and prevent further neurological deterioration. The definitive intervention is surgical untethering, recommended for patients experiencing new or worsening pain, neurological deficits, or bladder dysfunction. This procedure involves a neurosurgeon accessing the spinal cord through a laminectomy, separating the tissue attachments, and often sectioning the filum terminale.
For patients who are asymptomatic or have minimal symptoms, a strategy of watchful waiting with close surveillance is sometimes adopted instead of prophylactic surgery. However, in children with progressive neurological decline, early surgery is recommended to maximize the chance of symptom stabilization or improvement.
Following successful untethering, pain relief is the most consistently reported outcome, with improvement rates ranging from 70% to 100% in the short term. Long-term outcomes show that surgical untethering often stabilizes neurological function, though improvement in bladder dysfunction can be less predictable, especially in adults. A significant risk following the initial procedure is retethering, where scar tissue forms again and reattaches the cord. Revision surgery for retethering has less favorable outcomes than the primary procedure.