Radiculopathy
Description
- Dysfunction of a spinal nerve root -> dermatomal pain/sensory change + myotomal weakness + loss of the corresponding reflex
- LMN pattern - hypotonia, hyporeflexia, wasting; UMN signs mean the cord is involved as well (myeloradiculopathy)
- Radicular pain is sharp, electric, lancinating, radiating in a band - distinct from the deep, poorly localised referred (sclerotomal) pain of facet or disc disease
- Nerve root exits below the corresponding vertebra in the lumbar spine, but above it in the cervical spine
- Cervical: C6 root exits at the C5/6 level. There are 8 cervical roots and 7 cervical vertebrae, so C8 exits below C7
- A paracentral L4/5 disc typically hits the traversing L5 root, not the exiting L4 root - the commonest exam trap in disc-level localisation
Epidemiology
- Lifetime prevalence of lumbosacral radiculopathy ~3-5%; cervical ~1%
- L5 and S1 account for >90% of lumbar radiculopathies; C7 then C6 for cervical
- Peak 30-50 yrs for disc disease; >60 yrs for foraminal stenosis
- M slightly > F
Aetiopathogenesis
Structural
- Disc herniation - commonest under 50; L4/5 and L5/S1; C5/6 and C6/7
- Degenerative foraminal or lateral recess stenosis - commonest over 60; osteophyte, facet hypertrophy, ligamentum flavum
- Spondylolisthesis; scoliosis
- Trauma - fracture, root avulsion
Non-structural - the ones that get missed
- Malignant - vertebral or epidural metastasis, myeloma, leptomeningeal disease, nerve sheath tumour
- Infective - vertebral osteomyelitis/discitis, epidural abscess, herpes zoster (pain precedes the rash by days), Lyme, HIV, CMV, TB
- Inflammatory - diabetic lumbosacral radiculoplexus neuropathy (diabetic amyotrophy), sarcoidosis, vasculitis, CIDP variants
- Epidural haematoma; arachnoiditis; radiation plexopathy
Mechanism
- Mechanical compression + chemical irritation - nucleus pulposus glycoproteins and inflammatory mediators (TNF, PLA2) sensitise the root
- Explains why pain can be severe with minimal compression, and why most settle without the disc changing size
- Compression -> intraneural oedema, venous congestion, demyelination -> conduction block; axonal loss if prolonged
Diagnosis
- Clinical diagnosis. Imaging confirms the level; it does not make the diagnosis
- Asymptomatic disc bulges are present on MRI in ~30% at 20 yrs and >60% at 60 yrs - correlate or you will operate on the wrong thing
Upper limb - myotomes
| Movement | Root(s) |
|---|---|
| Shoulder abduction | C5/C6 |
| Elbow flexion | C5/C6 |
| Elbow extension | C7/C8 |
| Wrist flexion | C6/C7 |
| Wrist extension | C7/C8 |
| Finger extension | C7/C8 |
| Finger flexion | C7/C8 |
| Finger abduction/adduction | C8/T1 |
Upper limb - reflexes
| Reflex | Root |
|---|---|
| Biceps | C5/C6 |
| Supinator (brachioradialis) | C5/C6 |
| Triceps | C7/C8 |
- Inverted supinator jerk (absent supinator + finger flexion) = C5/6 root lesion with cord compression above
Lower limb - myotomes
| Movement | Root(s) |
|---|---|
| Hip flexion | L2/L3 |
| Hip adduction | L2/L3/L4 |
| Knee extension | L3/L4 |
| Hip abduction | L4/L5/S1 |
| Dorsiflexion | L4/L5 |
| Knee flexion | L5/S1 |
| Eversion | L5/S1 |
| Hip extension | L5/S1/S2 |
| Plantarflexion | S1/S2 |
Lower limb - reflexes
| Reflex | Root |
|---|---|
| Knee jerk | L3/L4 |
| Ankle jerk | S1/S2 |
- Inversion is L4 (tibialis posterior), eversion is L5/S1 (peronei) - the L5 vs peroneal nerve discriminator, together with hip abduction and the ankle jerk
The four common syndromes
| Root | Pain/sensory | Weakness | Reflex |
|---|---|---|---|
| C6 | Lateral arm -> thumb | Elbow flexion, wrist extension | Biceps, supinator |
| C7 | Middle finger | Elbow extension, wrist flexion | Triceps |
| L5 | Lateral leg -> dorsum of foot, great toe | Dorsiflexion, EHL, hip abduction, eversion | None (the reflex is normal - this is why L5 is missed) |
| S1 | Posterior leg -> lateral foot, little toe | Plantarflexion (test on tiptoes) | Ankle jerk |
Provocative tests
- Straight leg raise - positive if radicular pain reproduced at 30-70 degrees; sensitive, not specific (L4-S1)
- Crossed SLR is highly specific for disc herniation
- Femoral stretch (reverse SLR) - L2-L4
- Spurling test - neck extension + rotation + axial load, reproduces arm pain; specific, not sensitive for cervical radiculopathy
- Always examine for UMN signs, gait, saddle sensation and anal tone
Imaging
- **No imaging for acute radicular pain without red flags - it does not change management in the first 6 weeks**
- MRI if: red flags, progressive/severe neurological deficit, >6 weeks of failed conservative care, or surgery/injection contemplated
- CT or CT myelogram if MRI contraindicated
- Plain films only for instability, fracture, spondylolisthesis on flexion/extension
Neurophysiology
- EMG/NCS at >=3 weeks (needs time for denervation changes)
- Distinguishes radiculopathy from plexopathy, mononeuropathy and polyneuropathy
- Paraspinal denervation on EMG localises the lesion to the root (dorsal ramus, proximal to the plexus)
- Sensory nerve action potentials are PRESERVED in radiculopathy - the lesion is proximal to the dorsal root ganglion. The single most useful electrophysiological discriminator
Red flags
- Bilateral sciatica, saddle anaesthesia, bladder/bowel change -> cauda equina - MRI today
- Progressive or severe motor deficit (foot drop, quadriceps weakness)
- Fever, IVDU, immunosuppression, recent bacteraemia -> epidural abscess/discitis
- Age >50 with new pain, history of cancer, weight loss, night pain, thoracic pain -> malignancy
- Anticoagulation + acute severe pain -> epidural haematoma
- Trauma, osteoporosis, chronic steroid -> fracture
Management
A. Uncomplicated radicular pain - conservative first
- Most improve substantially within 6-12 weeks regardless of treatment; ~90% avoid surgery
- Stay active; avoid bed rest - explicitly counsel against it
- Physiotherapy - graded activity, McKenzie-type directional preference, core and hip strength; structured exercise, not passive modalities
- Explain the natural history and give a written self-management plan - this reduces imaging and opioid use more than any drug
B. Analgesia - modest expectations, honestly stated
- NSAID at the lowest effective dose for the shortest time (with GI, renal and cardiovascular caution)
- Paracetamol as an adjunct
- *Do NOT routinely offer gabapentin or pregabalin for sciatica - the PRECISE trial showed no benefit and more adverse effects; NICE recommends against gabapentinoids*
- This is a change from long-standing practice - and pregabalin is now a monitored medicine in Australia
- Avoid opioids where possible; if used, short course, immediate-release, with a stop date
- Amitriptyline or duloxetine only for established chronic neuropathic pain
- Oral corticosteroids give at best a small short-term functional benefit and are not routinely recommended
C. Interventional
- Transforaminal or interlaminar epidural steroid injection for acute severe sciatica not responding to conservative care
- Short-term (4-12 week) pain and function benefit; does not alter the need for surgery at 1 year
- Not for axial low back pain without radicular features
- Nerve root sleeve injection can also be diagnostic where the level is ambiguous
D. Surgery
- Emergency: cauda equina syndrome, progressive severe motor deficit, epidural abscess/haematoma, unstable fracture
- Elective (microdiscectomy or foraminal decompression) when all three hold:
1. Radicular pain persisting >6-12 weeks despite adequate conservative management, AND
2. Imaging shows a lesion that corresponds to the clinical level, AND
3. Disabling symptoms with the patient willing to accept the trade-off
- Surgery gives faster relief of leg pain; by 1-2 years outcomes converge with conservative care (SPORT) - frame the decision as speed of recovery, not final outcome
- Fusion adds nothing for uncomplicated disc-related radiculopathy - reserve for instability or deformity
E. Cause-specific
| Cause | Treatment |
|---|---|
| Herpes zoster radiculitis | Aciclovir/valaciclovir within 72 h; analgesia; consider amitriptyline for PHN |
| Malignant | Dexamethasone, urgent oncology/radiotherapy, treat the primary |
| Discitis/epidural abscess | Blood cultures + biopsy before antibiotics where safe; prolonged IV antibiotics +/- surgery |
| Diabetic amyotrophy | Glycaemic control, analgesia, physiotherapy; self-limiting over months, immunotherapy not routinely indicated |
| Inflammatory (sarcoid, vasculitis) | Corticosteroid + immunosuppression |
Associations
- Disc degeneration, smoking, obesity, heavy manual work, vibration exposure, sedentary posture
- Diabetes - both radiculoplexus neuropathy and worse outcomes from any radiculopathy
- Osteoporotic and pathological fracture
- Ankylosing spondylitis, DISH
- Malignancy - breast, lung, prostate, renal, thyroid, myeloma
- Herpes zoster (age, immunosuppression); HIV; Lyme disease
- Anticoagulation and recent neuraxial procedure
Natural history & complications
- Favourable in the great majority - ~75% substantially better by 12 weeks, most disc herniations resorb on serial imaging
- Larger extruded and sequestrated fragments regress MORE than small bulges
- ~5-10% come to surgery
- Recurrent disc herniation after discectomy ~5-10%
Predictors of a worse outcome
- Longer symptom duration before treatment
- Severe or progressive motor deficit
- Foraminal or extraforaminal (far lateral) herniation; bony stenosis rather than soft disc
- Smoking, obesity, diabetes
- Psychosocial yellow flags - work dissatisfaction, catastrophising, compensable injury, depression
Complications
- Persistent motor deficit - foot drop (poor recovery if weakness is severe and prolonged)
- Chronic neuropathic pain, central sensitisation
- Cauda equina syndrome if a large central herniation supervenes
- Deconditioning, opioid dependence, loss of employment
- Post-surgical: recurrent herniation, dural tear/CSF leak, discitis, epidural fibrosis, failed back surgery syndrome
Monitor
- Serial power (especially dorsiflexion and plantarflexion), reflexes and gait
- Ask about bladder and bowel function at every review
- Analgesic use and opioid escalation
- Return-to-work and functional milestones
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