The spinal cord serves as the central information highway connecting the brain to the rest of the body, traveling through the protective spinal column. Normally, the spinal cord is unattached and moves freely within the bony canal, allowing it to glide slightly with the body’s flexing and bending motions. This flexibility prevents physical stress on the delicate neural tissue. Tethered Cord Syndrome (TCS) is a neurological disorder where the lower portion of the spinal cord is abnormally anchored by surrounding tissues. This fixation prevents the cord’s normal movement, subjecting it to damaging tension, especially as the body grows or moves.
Defining Tethered Cord Syndrome (TCS)
The spinal cord typically terminates in a tapered structure known as the conus medullaris, usually located at the level of the first or second lumbar vertebra in adults. From this point, a thin, fibrous tissue called the filum terminale extends downward, anchoring the spinal cord to the coccyx. In TCS, this final portion is abnormally attached to the surrounding structures of the spinal canal, often by a thickened filum terminale or scar tissue.
This abnormal attachment, or “tethering,” prevents the conus medullaris from ascending naturally as the vertebral column lengthens during growth. The restriction causes the lower spinal cord to be stretched taut, especially during forward flexion or growth spurts. The resulting mechanical stress impairs the local blood supply to the lower segments of the cord. This reduction in blood flow leads to metabolic dysfunction and compromises nerve cell function.
The continuous stretching and resulting lack of oxygen supply compromise the function of the nerve fibers that control the legs, bladder, and bowels. This constant, abnormal tension exceeds the spinal cord’s natural stretch tolerance, leading to progressive neurological and functional decline.
Recognizing the Signs and Symptoms
The manifestations of tethered cord syndrome differ significantly depending on the patient’s age, often presenting subtle yet progressive changes. In infants and young children, signs are frequently visible on the skin over the lower back, referred to as cutaneous markers. These markers can include:
- A patch of excessive hair growth.
- A deep dimple.
- A discolored skin patch.
- A fatty lump known as a lipoma.
Orthopedic issues often appear early, such as foot deformities, differences in leg length, or a progressive curvature of the spine called scoliosis. Children may also exhibit motor changes like weakness in the legs, an awkward gait, or difficulty with activities like running. Dysfunction of the bladder and bowels is a common sign in pediatrics, manifesting as difficulty emptying the bladder, frequent urinary tract infections, or chronic constipation.
In older children, adolescents, and adults, the presentation focuses on chronic pain and worsening neurological function. Chronic lower back pain is a common complaint, often radiating into the legs, groin, or perineal region. Sensory changes are also reported, including numbness, tingling, or loss of sensation in the legs and lower back.
Neurogenic bladder issues, involving a loss of bladder control or difficulty retaining urine, are frequently observed due to damage to the sacral nerves. Changes in walking, such as a foot drop or increasing weakness in the lower limbs, may also develop, reflecting the progressive strain. Symptoms in adults may begin or worsen following trauma, strenuous physical activity, or during periods of rapid weight gain or pregnancy.
Causes and Associated Conditions
Tethered cord syndrome arises from various underlying anatomical abnormalities, categorized based on whether they are present at birth or develop later in life. Congenital TCS is the most common form, resulting from developmental issues during the formation of the spinal column and cord in utero. The most frequent congenital cause is tight filum terminale, where the fibrous strand at the end of the spinal cord is abnormally short, thick, or inelastic.
Another cause is the association with spinal dysraphism, a group of birth defects that includes spina bifida. In cases of lipomyelomeningocele, a benign fatty tumor forms at the lower end of the spinal cord, physically anchoring the conus medullaris to the surrounding tissue. Other congenital causes include diastematomyelia, where the spinal cord is split into two halves, or a dermal sinus tract, a small channel connecting the skin to the spinal canal.
Secondary, or acquired, tethered cord syndrome occurs when fixation develops later in life due to external factors. The most frequent cause of acquired TCS is scar tissue following previous spinal surgery, especially those performed to repair congenital defects like myelomeningocele. This scar tissue can adhere to the spinal cord or nerve roots, limiting movement and causing tension. Trauma to the spine or spinal infections leading to inflammation and fibrous adhesions can also result in acquired tethering.
Diagnosis and Management Options
The diagnosis of tethered cord syndrome relies on clinical assessment and specialized medical imaging. A neurological examination evaluates motor function, sensation, reflexes, and the presence of any cutaneous markers on the lower back. Urodynamic studies, which test bladder function, are often included, as bladder dysfunction is one of the earliest and most reliable signs of the condition.
Magnetic Resonance Imaging (MRI) is the gold standard diagnostic tool, providing detailed, non-invasive images of the spinal cord, nerve roots, and surrounding soft tissues. An MRI confirms the diagnosis by revealing a low-lying conus medullaris, typically positioned below the L2 vertebral level in adults, and identifies the underlying pathology like a thickened filum terminale or a lipoma. In complex or subtle cases, specialized imaging like prone or upright MRI scans may be used to visualize the cord under tension.
Management approaches for TCS vary depending on the severity of symptoms and the patient’s age. For patients who are asymptomatic or whose symptoms are mild and non-progressive, careful observation may be recommended. This involves regular follow-up appointments and imaging to monitor for signs of worsening neurological or functional status.
The definitive treatment for symptomatic or progressively worsening tethered cord syndrome is a surgical procedure known as detethering. The goal of this microsurgery is to locate and release the abnormal attachment, restoring the spinal cord’s normal mobility and relieving mechanical tension. Surgical intervention is recommended when there is clear evidence of progressive symptoms, as earlier treatment offers the best chance to prevent irreversible neurological damage.