Sciatica and Lumbosacral Radiculopathy
Sciatica is radiating leg pain in a sciatic nerve distribution, usually caused by lumbosacral radiculopathy affecting the L4–S1 nerve roots. Lumbosacral radiculopathy refers to compression, irritation or inflammation of the lumbar and/or sacral nerve roots, commonly due to intervertebral disc herniation, spondylosis, spondylolisthesis or spinal canal stenosis.
Definitions and Anatomy
| Term | Definition |
|---|---|
| Radiculopathy | Compression / irritation / inflammation of a spinal nerve root |
| Lumbosacral radiculopathy | Radiculopathy affecting the lumbar and/or sacral nerve roots |
| Sciatica | A clinical symptom / presentation: radiating pain down the leg in a sciatic nerve distribution, usually due to lumbosacral radiculopathy affecting L4–S1 |
Causes and Risk Factors
Key causes:
- Herniated intervertebral disc (“slipped disc”) – causes ~90% of cases
- Most commonly occur at L5/S1 level
- Most commonly caused by age-related degenerative changes (rarely by trauma)
- Spondylolisthesis
- Spondylosis
- Spinal canal stenosis
Rare causes:
- Infection (e.g. discitis, vertebral osteomyelitis, spinal epidural abscess)
- Metastatic cancer (esp. breast, prostate and lung cancer)
Risk factors:
- Older age (peak incidence: 45-64 y/o)
- Genetic factors (influences disc degeneration)
- Smoking
- Obesity
- Occupational factors
- Whole body vibration (e.g. due to driving, operating machinery)
- Strenuous physical activity (e.g. frequent heavy lifting, esp. while bending and twisting)
Clinical Features
Sciatica
Typical features:
- Low back pain
- Unilateral leg pain radiating below the knee to the foot and/or toes
- Sensory and/or motor changes in a dermatome / myotome distribution (see below)
- +ve Straight leg raise test
- Test description: patient in supine position, the hip is passively flexed with the knee extended
- +ve Finding: pain is reproduced <60 degrees of hip flexion
If sciatica is secondary to spinal canal stenosis:
- Neurogenic claudication (lower back and buttock pain radiating down the thighs and legs that is triggered on walking or prolonged standing)
- The key feature to differentiate spinal canal stenosis from peripheral arterial disease (vascular claudication) is that there would be normal pulses, skin colour, temperature, and CRT in neurogenic claudication
- Pain improves with spine flexion (e.g. sitting, walking uphill) and worsens with spine extension (e.g. standing upright, walking downhill)
- “Shopping cart sign”: patient tends to lean forward on a shopping cart or walker while walking to relieve symptoms (as this flexes the spine and creates more space inside the spinal canal)
Nerve Root-Specific Findings
Non-specific findings include:
- Numbness / paraesthesia / pain / burning sensation in the corresponding sensory distribution
- Weakness in the corresponding motor distribution
- Reduced / absence of reflex, depending on the affected nerve root
| Affected nerve root | Sensory changes | Motor weakness | Affected reflex |
|---|---|---|---|
| L2 | Groin + upper thigh | Hip flexion | Reflexes are often spared |
| L3 | Anterior thigh | Hip flexion +/- knee extension | Patellar reflex (L3-L4) |
| L4 | Anterior thigh + patella + medial leg | Knee extension +/- dorsiflexion | |
| L5 | Lateral leg + dorsum of the foot (including big toe) | Dorsiflexion (→ foot drop) +/- big toe extension | Reflexes are often spared |
| S1 | Sole of the foot + posterior calf / thigh | Plantarflexion +/- foot eversion | Achilles reflex (S1-S2) |
| S2-S4 |
Perineum / perianal region / saddle area |
No major limb weakness | Perineal reflex / bulbocavernosus reflex may be reduced |
Note: Dermatomal maps and myotomal distributions vary between sources and may differ between individual patients in clinical practice.
The findings presented above represent typical patterns that can be useful for exams and as a guide in clinical assessment.
L5 radiculopathy vs common peroneal nerve palsy
| Feature | L5 radiculopathy | Common peroneal nerve palsy |
|---|---|---|
| Structure involved | L5 nerve root exiting the lumbar spine | Common peroneal nerve (branch of the sciatic nerve) near the fibular neck |
| Common causes | Lumbar disc herniation | Leg crossing, prolonged lateral decubitus position, lateral knee trauma |
| Motor function | Weakness in:
|
Weakness in:
Ankle inversion is spared in common peroneal nerve palsy as it is performed by the anterior tibialis, which is innervated by the tibial nerve. |
| Sensory function | Lateral leg + dorsum of the foot
Often accompanied by lower back pain and +ve straight leg raise test |
Lateral leg |
| Reflexes | Reflexes are typically normal | |
Back Pain Red Flags
| Serious underlying condition to exclude | Key red flags |
|---|---|
| Cauda equina syndrome |
|
| Spinal fracture |
|
| Cancer |
|
| Infection (e.g. discitis, vertebral osteomyelitis, spinal / epidural abscess) |
|
TUNA FISH is a mnemonic / clinical screening tool used for low back pain red flags:
- T: trauma
- U: unexplained weight loss
- N: neurological symptoms (esp. saddle anaesthesia, loss of bowel or bladder control)
- A: age (<20 or >50 y/o carries a higher risk of serious non-mechanical causes)
- F: fever
- I: IVDU
- S: steroid use
- H: history of cancer
Investigation and Diagnosis
Clinical diagnosis (based on clinical history and physical examination)
Consider using the STarT Back risk assessment tool for risk assessment and stratification to guide management
DO NOT routinely offer imaging (including lumbar X-rays and MRI) in a non-specialist setting
Only consider imaging in a specialist setting if the result is likely to change management
Management
First, exclude red flags that may suggest a serious underlying cause
- If cauda equina syndrome or spinal fracture is suspected → emergency referral to a spinal surgery service
- If cancer or infection is suspected → urgent referral to a spinal surgery service or urgent MRI within 2 weeks
Choice of management based on risk stratification:
- Likely to have a good outcome (e.g. low risk of chronicity on STarT Back) → simpler and less intensive support (e.g. reassurance + advice to keep active + guidance on self-management)
- Higher risk of a poor outcome (e.g. high risk of chronicity on STarT Back) → more complex and intensive support (e.g. exercise programmes +/- manual therapy or psychological approach)
Conservative / General Management
Advise to:
- Stay active and continue normal activities as much as possible
- Perform exercises that promote strength, flexibility and aerobic fitness
Offer:
- Structured exercise programme
- +/- Manual therapy (e.g. spinal manipulation, mobilisation or massage)
- +/- Psychological therapies using a CBT approach
Do NOT offer the following:
-
Belts, corsets, foot orthotics, and shoes
-
Manual traction therapy
-
Acupuncture
-
Electrotherapies (including: ultrasound, TENS, PENS, interferential therapy)
Pharmacological Management
- 1st line: oral NSAIDs (use the lowest effective dose for the shortest possible period of time)
- 2nd line: weak opioid +/- paracetamol
Do NOT offer paracetamol alone
Do NOT offer the following:
- Gabapentinoids (pregabalin and gabapentin) and other antiepileptics
- Benzodiazepines
- Corticosteroids
- Opioids
- SSRIs, SNRIs, TCAs
Interventional / Invasive Management
| Intervention | Indications |
|---|---|
| Radiofrequency denervation | Consider referring for assessment if ALL of the following are met:
Only perform radiofrequency denervation after a +ve response to diagnostic medial branch block. |
| Epidural injection of LA and steroids | Consider in acute and severe sciatica
Otherwise, do not routinely offer spinal injections |
| Surgical spinal decompression | Consider if:
|
Do NOT routinely offer the following:
- Disc replacement
- Spinal fusion (unless in a specialist setting where other interventions have been unsuccessful and the indication is clearly established)