Tethered spinal cord syndrome (TCS) is a neurological condition where tissue attachments restrict the movement of the spinal cord within the spinal column. This abnormal fixation causes the spinal cord to be stretched, limiting its ability to slide freely during movement and growth. This mechanical stretching interferes with blood flow and damages the nerve signals traveling through the cord. If the tension is not relieved, this stretch-induced disorder can lead to progressive neurological damage and permanent functional deficits.
The Mechanism of Tethering
The normal spinal cord ends in the conus medullaris, typically positioned around the first or second lumbar vertebra in adults. A fibrous thread, the filum terminale, extends from the conus and anchors the spinal cord to the tailbone. In a healthy spine, the conus and filum move freely within the spinal canal as the body grows and flexes.
Tethering occurs when the conus medullaris is held abnormally low (at or below the second lumbar vertebra) or when the filum terminale is inelastic, thickened, or attached to abnormal tissue. This fixation prevents the spinal cord from ascending normally as the vertebral column grows, creating constant, abnormal tension. This tension is exacerbated by everyday movements like bending or stretching.
The physical stretching restricts the blood supply (ischemia) to the lower segments of the spinal cord. This lack of oxygen impairs nerve function, leading to metabolic derangement. This chronic traction eventually causes progressive deterioration of motor, sensory, and autonomic functions.
Identifying the Signs
Symptoms often progress or worsen over time, particularly during periods of rapid physical growth. They are broadly categorized into neurological, orthopedic, and cutaneous signs. Neurological issues include changes in bladder and bowel control, such as urinary retention or incontinence. Patients frequently report severe low back pain or shooting pain that radiates down the legs, sometimes extending into the perineum or genital area.
Muscle weakness and sensory changes in the lower extremities are common findings. This leads to difficulty walking, an altered gait, or a noticeable difference in the strength or size of the legs. Deterioration in motor function can also manifest as orthopedic problems, such as foot deformities like a high arch (pes cavus) or curled toes (claw toes). Scoliosis, an abnormal side-to-side curvature of the spine, is frequently observed.
Visible skin markers on the lower back, known as cutaneous stigmata, may serve as early indicators of an underlying spinal issue. These external signs are present in many affected patients and should prompt further investigation. These markers include:
- Deep dimples
- Tufts of hair
- Skin tags
- Hemangiomas
- Areas of pigmented or discolored skin over the lumbosacral region
Underlying Causes and Risk Factors
TCS can be congenital (present at birth due to developmental anomalies) or acquired later in life. The majority of cases are congenital and associated with spinal dysraphism.
One major cause is myelomeningocele, the most severe form of spina bifida, where the spinal cord fails to separate properly from the skin during embryonic development. Even after surgical repair, the cord remains low-lying and susceptible to re-tethering.
Another common cause is lipomyelomeningocele, where an abnormal fatty growth (lipoma) connects to the spinal cord and its membranes. This fatty tissue restricts the cord’s movement by anchoring it to the spinal canal. A third frequent cause is a thickened or abnormally tight filum terminale, which prevents the conus medullaris from ascending.
Less common congenital causes include a split spinal cord (diastematomyelia) or a dermal sinus tract. Acquired tethering typically results from scar tissue formation following previous spinal surgery or injury, which adheres to the spinal cord and restricts its mobility.
Diagnosis and Surgical Management
Diagnosis begins with a neurological and physical examination to assess symptoms and check for cutaneous markers. Imaging studies confirm the presence and location of the tethering structure. Magnetic Resonance Imaging (MRI) is the gold standard diagnostic tool, providing detailed views of the spinal cord, nerve roots, and surrounding tissues.
MRI can reveal a low-lying conus medullaris, a thickened filum terminale, or abnormal fatty tissue or tumors tethering the cord. In infants, an ultrasound may be used as an initial screening tool to visualize spinal cord movement. Urodynamic testing is often performed to assess the function of the lower urinary tract, particularly regarding bladder control.
Treatment for symptomatic TCS is almost exclusively surgical, known as detethering surgery. The primary goal is to free the spinal cord from its abnormal attachments to relieve tension and prevent further neurological deterioration. The surgery typically involves a laminotomy or laminectomy, where a portion of the bony vertebrae is removed to access the spinal cord.
The neurosurgeon dissects and removes the tethering structure, such as the thickened filum terminale, scar tissue, or lipoma, allowing the spinal cord to float freely. While surgery often stabilizes or improves symptoms, re-tethering is possible, especially in growing children or due to new scar tissue formation. Early diagnosis and intervention are associated with better outcomes for preventing irreversible neurological damage.