Tethered Cord Syndrome

Tethered cord syndrome is a stretch induced functional disorder of the spinal cord caused by abnormal fixation of the conus medullaris, which lies caudal to the L2 vertebral level, by a thickened filum terminale, lipoma, fibrous band or scar. It causes progressive neurological, urological and orthopaedic dysfunction.

It is found mainly in children with spinal dysraphism, and can first present in adults (often in the 30s to 50s), sometimes after pregnancy, trauma or lumbar spine surgery.

Causes. Thickened filum terminale (over 2 mm), lipomyelomeningocele, lipoma of the filum or conus, diastematomyelia, dermal sinus, myelomeningocele repair scar and previous spinal surgery.

Pathophysiology. Traction reduces spinal cord blood flow and causes oxidative metabolic impairment of the conus, leading to ischaemic neuronal injury.

Presentation is back and perineal pain, leg pain, progressive weakness, sensory loss, urinary urgency, frequency, retention or incontinence, bowel dysfunction, sexual dysfunction, foot deformity (pes cavus), scoliosis and gait disturbance. Cutaneous markers (hairy patch, dimple, haemangioma, lipoma) overlie the lower spine in children. Pain may worsen with flexion.

Red flags.

• New or worsening bladder or bowel dysfunction.
• Progressive weakness or foot deformity.
• Rapid progression after pregnancy, trauma or surgery.

MRI of the lumbosacral spine (low lying conus, thick filum, lipoma, syrinx). Ultrasound screens infants under 3 to 6 months. Urodynamic studies measure bladder function. Electromyography and somatosensory studies show denervation. Assess for associated anomalies (renal ultrasound, orthopaedic review).

Differential diagnosis.

• Lumbar spondylosis, disc herniation and spinal stenosis.
• Cauda equina compression, spinal tumour and hereditary spastic paraplegia.
• Normal variation of conus position, and neurogenic bladder from other disease.

Surgery. Untethering (division of the filum terminale or release of the tether) for symptomatic or progressive disease, performed with intraoperative neurophysiological monitoring. Benefits are best for pain and early deficits, and bladder recovery is variable. Risks include CSF leak, wound problems, retethering (10 to 20% over years) and new deficit.

Observation. For asymptomatic patients with a low lying conus, with regular review.

Symptom control. Neuropathic pain: gabapentin 300 mg daily, increased to 600 mg three times daily (adjusted to eGFR), or amitriptyline 10 to 75 mg at night. Bladder: clean intermittent catheterisation for retention, with antimuscarinics (oxybutynin 2.5 to 5 mg two or three times daily).

Rehabilitation. Physiotherapy, orthotics and orthopaedic care.

Monitoring. Neurological examination, bladder function and imaging when symptoms change, because retethering can occur years later.

Referral and escalation. Refer to neurosurgery and urology. Refer urgently for acute bladder or bowel loss or rapidly progressive weakness.

Special groups. In pregnancy, symptoms can worsen as the uterus enlarges. Plan delivery with neurosurgery and anaesthesia. In children, surgery is often done early in those with lipomas or dermal sinuses.