Tethered Cord Syndrome (TCS) is a syndrome in which the spinal cord or conus is stretched by various congenital or acquired causes and the conus descends, resulting in a series of neurological dysfunctions. It was named by Yamada in 1981. It is generally accepted that TCS can be considered when the cone of the spinal cord is below the L2 vertebra or the diameter of the terminal filament is greater than 2 mm.
Onset
In early embryonic development, the spinal cord and the spinal canal are approximately equal in length. Subsequently, the spinal column grows faster than the spinal cord, resulting in a gradual upward shift in the position of the spinal cord. In infants, the cone is located at the lower edge of the L3 vertebrae at birth, and the tip of the cone rises to the lower edge of the L1 vertebrae or the upper edge of the L2 vertebrae as it develops between the second month of life and adulthood. The spinal cord cone also gradually becomes thinner and moves to the terminal filament (less than 2 mm in diameter in adults), and the distal end of the terminal filament in adults is usually attached to the dorsal side of the inner wall of S5.
In the process of spinal cord upward migration, the cone, cauda equina, and end filaments are pulled and compressed due to various causes of spinal cord end retraction, resulting in cone traction and dysplasia, which is the primary TCS; the spinal cord and dura mater are easily adhered after spinal cord expansion repair, tumor, etc., which affects upward migration and can cause secondary TCS.
Pathophysiology
The spinal cord is altered in terms of neurophysiological function and tissue metabolism at the site of the spinal cord strain. The main causes are decreased blood flow to the spinal cord, decreased oxygen supply, impaired oxidative metabolism, and decreased metabolism of neuronal and glial cells. The susceptibility of each segment of the spinal cord to strain also differs. Due to the buffering effect of the dentate ligament, the closer to the caudal end, the greater the impact of end-filament strain on the spinal cord, with the sacrococcygeal segment being the most vulnerable, followed by the lumbar segment. The less the pulling force and the shorter the time, the lighter the metabolic impairment and the better the reversibility after release of the embolus.
Main symptoms and signs
Pain is the most common symptom of TCS in adults. Rectal, mid-buttock, sacrococcygeal, perineal, low back and lower extremities. Lower extremity pain is often widely distributed and exceeds a single innervated area of nerve roots. Pain is often caused by prolonged sitting, excessive body flexion, etc
Motor impairment It may manifest as upper motor neuron damage or lower motor neuron damage. Progressive lower extremity weakness and difficulty walking. Muscle atrophy, foot and ankle deformities such as high arched feet and hammertoes may develop over time.
Sensory impairment Mainly numbness or hypoesthesia of the skin in the saddle area. Rarely, there is an obvious plane of sensory impairment.
Bladder dysfunction Neurogenic bladder resulting in urinary incontinence, which may be combined with renal impairment
Rectal dysfunction Loss of nerve in the pelvic floor muscles and external anal sphincter, making defecation difficult, constipation, and also fecal retention and incontinence
Abnormal skin nutrition
Combined malformations Lumbosacral skin abnormalities, including subcutaneous masses, cutaneous sinus tracts, spinal bulges, hemangiomas, and hirsutism Musculoskeletal deformities, including scoliosis, hyperkyphosis
Diagnosis
X-rays can show bony abnormalities, such as spina bifida and other deformities
CT can further reveal abnormal spinal changes
MRI is the primary means of diagnosing the disease, with images of the spinal cord remaining below L3 and the cone being stretched and thinned to terminate at the sacrococcygeal region. It can show abnormal lesions in the spinal canal such as lipomas, bony crests, dermatomal sinuses, tumors, etc.
Classification
Pure end-filament distraction type
Spinal cord distension with adhesions
Fatty spinal cord distension pull type
Dorsal subcutaneous sinus tract pulling and compressing type
Spinal cord longitudinal fibers, cartilage or crest, and spinal membrane pulling type
Terminal spinal cord cysts
Scar adhesions secondary to surgery
Indications for surgery
The purpose of surgery is to release the strain and compression, so that the spinal cord can be loosened to facilitate the restoration of microcirculation in the strained area and to promote the recovery of nerve function or the gradual recovery of nerves that have not degenerated. Asymptomatic primary TCS may produce neurological impairment at any time, but there is uncertainty as to whether spinal cord embolization necessarily leads to neurological impairment and whether the process can be artificially interrupted after neurological impairment. Indications for surgery for secondary TCS: clinical manifestations of re-aggravation of existing symptoms or new manifestations of neurological impairment, urodynamic testing to evaluate the degree of neurological impairment, and neurophysiological testing.
Surgical steps
Anesthesia and position: general anesthesia with endotracheal intubation, all in prone position with the lumbosacral region at the highest point to prevent CSF loss
Incision: Usually a posterior median incision is used, but for those with small concave or obvious bulging skin, a longitudinal or transverse shuttle incision is made to fully reveal the spina bifida and lesion.
Exposure: layer-by-layer incision of skin, subcutaneous fat, and deep fascia, with excision of degenerative skin, subcutaneous scar, fat pad, subcutaneous fistula, and other tissues along the way
Laminectomy: Expose the normal segment from the head and tail of the spina bifida, perform subperiosteal separation of the paravertebral muscles to expose the normal spinous process and bilateral laminae of the head and tail, and perform laminectomy of the normal segment. The normal dural layer was exposed, and the dura was gradually revealed towards the lesion, and all the scar, cartilage, hyperplastic bone and ligamentum flavum at the spina bifida were removed to release the epidural compression and pulling factors and isolate the bulging structures. External end filaments are seen in the lower sacral segment, and in some cases the dural sac rises after severance. In the case of spinal cord lipoma, the spinal cord spinal membrane is seen to bulge from the spina bifida and break through the dura to connect the lipoma to the subcutaneous fat pad
Subdural operation: performed under the microscope, according to the above etiological typology
Suturing: After complete hemostasis, the subdural cavity is flushed clear with saline. After inventorying cotton, gauze and instruments without errors, take 4-0 non-invasive sutures to continuously close the dural layer, reconstruct the complete dural sac and reconstruct the end pool. Suture the paravertebral muscle, fascial layer, subcutaneous tissue, and skin
Postoperatively: keep prone position for 1-2 weeks, press sandbags at the incision, use antibiotics as appropriate
Surgical complications
Headache is common and is associated with more intraoperative cerebrospinal fluid loss and postoperative hypocranial pressure. Methods of prevention include tilting the operating table head side down at 30° during surgery. Tight suturing of the dura and injection of saline into the dural sac prior to complete closure to replace cerebrospinal fluid
Transient neurological damage usually occurs within 6 weeks after surgery and is characterized by urinary retention, decreased muscle strength in the lower extremities, and urinary incontinence, which is usually restored to preoperative levels within 6 weeks after surgery with conservative treatment. Permanent damage is dominated by sphincter symptoms
Cerebrospinal fluid leak and pseudospinal bulge Cerebrospinal fluid leak is related to the quality of the dural repair, paravertebral muscle suture technique, and sometimes the need to preserve some of the subcutaneous lipoma
Infection Most often occurs in patients with postoperative cerebrospinal fluid leak, skin sinus resection, and dural sac repair with artificial material
Re-embolization A distant complication, closely related to the type of embolism, the degree of surgical release, and the surgical approach, most often occurring in patients with open spina bifida and conoidal lipoma postoperatively. The incidence is 5% to 33%. Enlargement of the dural sac to accommodate the cerebrospinal fluid allows the spinal cord and nerve roots to soak freely in the cerebrospinal fluid, which helps prevent re-embolization
Surgical efficacy
Evaluation indicators.
Cure: normalization of defecation and urination
Improvement: there is a significant improvement in defecation, urination and limb lesions
No change: Same symptoms as before surgery
Deterioration: symptoms are worse than before surgery or new symptoms appear on the basis of the original symptoms
Cure and improvement were considered effective
The results of the study concluded that the original neurological symptoms could be maintained or improved after surgery. However, the postoperative results are not the same for different pathological types.
In adult TCS, surgery is effective for pain, lower extremity weakness and spasticity, but less effective for urinary and fecal dysfunction. In children with TCS, spinal cord bulge is the most common cause, and surgery is more effective for lower extremity weakness, pain and sensory impairment, but less effective for urinary and fecal dysfunction.
It is difficult to cure the dysfunction of urinary and fecal function with surgery, and only surgery before or at the early stage of symptoms can preserve the function of urinary and fecal function, and it usually takes 0.5-1 year to reach a stable level of symptom relief, and some can take up to 6-7 years, which may be related to the irreversible damage caused by long-term stretching and ischemia at the end of the spinal cord.
If the cone pulsation is abnormal after surgery, the symptoms are often present in the urine and stool or both lower extremities; if the cone pulsation is transformed from normal to abnormal, the symptoms often recur; if the cone is neither pulsating nor moving with breathing before surgery, the prognosis after surgery is poor; if the cone pulsation is normal, most of the symptoms disappear or get better