Pathophysiology

  • Compression and Irritation of the lumbosacral nerve roots (L4, L5, S1) forming the sciatic nerve causes radiating pain in the back, buttock or down the leg
  • Causes of lumbar radiculopathy include:
    • Herniated intervertebral disc - the most common cause, usually secondary to degenerative spinal changes
    • Spondylolisthesis - the forward-slippage of the proximal vertebrae relative to the vertebra below
    • Spinal stenosis

Clinical features

  • Lower back pain
  • Unilateral leg pain which radiates into the buttock, or down the leg and often into the foot - often ‘shooting’ or ‘burning’ pain
  • Examination
    • Dermatomal paraesthesia or sensory changes
    • Myotomal weakness 
    • Reflex impairment - diminished knee jerk (if L4 affected) or ankle jerk reflex (if S1 affected
    • Straight leg raise (SLR) - radiating pain is felt when the hip is flexed to between 30 and 60 degrees. 
      • The leg can be lowered to just below the pain threshold and then ankle dorsiflexion applied to differentiate between MSK and lumbosacral radiculopathy (Bragard test)

Investigations

  • If bony injury suspected - CT
  • If neurologic deficit is present - MRI is 1st line in establishing the causes of radiculopathy 
  • If there are no red flags, consider using the STarT Back risk assessment tool to inform management.
    • It is a nine item questionnaire which stratifies patients as low, medium or high risk of persistent back pain related disability.

Management

  • Analgesia 
    • For back pain - 1st line NSAIDs, alt: codeine +/- paracetamol
    • For sciatica - NICE advises: Do NOT offer gabapentinoids due to lack of evidence and SEs, do NOT offer opioids for chronic sciatica, be aware of limited evidence for NSAIDs
  • Offer self-management advice - symptoms usually settle within a few weeks to months, exercise is important
  • Refer to specialist if:
    • Severe radicular pain at 2-6 weeks
    • Non-tolerable radicular pain at 6 weeks
    • Acute and severe sciatica - for consideration of spinal injection
    • For consideration of spinal decompression if non-surgical measures have failed 

References:

NICE CKS. Sciatica (lumbar radiculopathy) [September 2023]. Available here.