Lumbar Spinal Stenosis

Lumbar spinal stenosis is caused by narrowing of the spinal canal or neural foramina producing root ischaemia and neurogenic claudication. Stenosis of the spinal canal is most often caused by a combination of loss of disc space, osteophytes and a hypertrophic ligamentum flavum. Not all patients with narrowing develop symptoms and lumbar spinal stenosis therefore refers to a clinical syndrome of lower extremity pain caused by mechanical compression on the neural elements or their blood supply.¹

• Most often occurs in those aged 60 years or older.²
• Although symptoms may arise from narrowing of the spinal canal, not all patients with narrowing develop symptoms.¹

Risk factors

• Congenital narrowing of the spinal canal (much less common than degenerative)
• Degenerative, osteoarthritis
• Hyperparathyroidism
• Paget's disease
• Ankylosing spondylitis
• Cushing's syndrome
• Acromegaly

• Gradual onset of unilateral or bilateral leg pain (with or without back pain), numbness, and weakness developing after patient walks a predictable distance. Affected patients may have less difficulty walking uphill rather than down.
• About half of all patients present with back pain, which is usually bilateral and diffuse over the buttocks.
• Neurogenic intermittent claudication: leg fatigue and/or weakness and leg numbness and/or paraesthesiae
• Pain:
  • Bilateral leg pain with burning or cramping. Involves buttocks and thighs and spreads to the feet.
  • The neural canal and neural foramen are narrowed with the spine in extension and opened in flexion, neural compression is usually intermittent and provoked by lying prone or extending the lumbar spine and when upright, particularly when walking.
  • Cycling does not usually cause significant problems.
  • The pain is usually relieved by sitting, leaning forward, putting the foot on a raised cushion or stool, or lying supine.
• May cause cauda equina compression:
  • Caused by any narrowing of the spinal canal that compresses the nerve roots below the level of the spinal cord.
  • May be due to trauma, disk herniation, spinal stenosis, spinal neoplasms, inflammatory or infectious conditions.
  • Features of cauda equina compression include low back pain, unilateral or bilateral sciatica, saddle and perineal anaesthesia, bowel and bladder disturbances, and weakness, sensory deficits and reduced or absent reflexes in the legs.
• Assessment requires a complete motor and sensory neurological examination, which is often normal.
• Lower limb vascular examination is also necessary to rule out vascular claudication.

• Peripheral vascular disease
• Spinal neoplasms: benign, malignant and metastatic
• Large central disc herniation
• Spondylolisthesis: degenerative lumbar vertebra subluxation
• Lumbar spine trauma or vertebral fracture
• Epidural abscess
• Inflammatory arachnoiditis

• Lumbar spine x-ray:
  • Initial assessment for a possible alternative diagnosis.
  • Degenerative spine changes: disk space narrowing is a poor predictor of symptoms.
  • May demonstrate underlying abnormality, e.g. occult spina bifida, spondylolisthesis.
• Lumbar spine MRI (the preferred investigation) or CT scan:³
  • MRI is the first choice because CT myelogram is invasive.
  • CT myelogram is preferred if a better delineation of the bony anatomy and the specific nerve root involvement is necessary.
  • CT scan alone is not as helpful but it is an alternative if MRI or CT myelogram are not available.

• Weight reduction if overweight.
• Physiotherapy with flexion exercises.
• Non-steroidal anti-inflammatory drugs; other medication for pain relief as appropriate.
• Epidural anaesthetic blocks may be helpful for a minority of patients. There is some debate as to whether epidural corticosteroids have any additional benefit over anaesthetic block alone.^4,5
• Surgical decompression: decompressive laminectomy may be effective for those patients who do not respond to conservative measures.⁶
• There is only limited evidence for the benefits of surgical intervention for degenerative lumbar spinal stenosis.⁷
• Interspinous distraction procedures involve the insertion of a device that is implanted between the spinous processes that reduces extension at the symptomatic level (most commonly L3-L5) but allows flexion and unrestricted axial rotation and lateral bending. The guidance from NICE is that there is insufficient evidence of benefit for these procedures to be recommended.⁸
• Cauda equina compression usually requires urgent surgical decompression.

The prognosis of conservative treatment is relatively good unless a complete block is shown in the myelogram.⁹