Key Facts

CES is a surgical emergency with a narrow therapeutic window. Delayed diagnosis is a major source of medicolegal claims. Any patient with bilateral leg symptoms, saddle numbness, or urinary dysfunction with back pain must have urgent assessment.

Epidemiology

Relatively uncommon: ~2-6% of lumbar disc herniations. Annual incidence ~1 per 33,000-100,000. Affects adults 30-50 years most commonly (disc herniation age group).

Aetiology

• Lumbar disc herniation (most common — 45%): large central disc at L4/5 or L5/S1
• Spinal tumour: metastasis, schwannoma, ependymoma of filum terminale
• Spinal stenosis: chronic degenerative, acute-on-chronic
• Epidural abscess or haematoma
• Trauma: fracture-dislocation
• Post-surgical: haematoma, re-herniation

Pathophysiology

The spinal cord terminates at L1/L2 as the conus medullaris. Below this, the spinal canal contains the cauda equina (bundle of lumbar, sacral, and coccygeal nerve roots). These are peripheral nerves (LMN), NOT spinal cord → produces LMN pattern (flaccid, areflexic) rather than UMN pattern. Compression causes ischaemia and demyelination of nerve roots. S2-S4 roots control bladder, bowel, and sexual function and are especially vulnerable.

Symptoms

• Bilateral sciatica: pain radiating down both legs (may be asymmetric)
• Saddle anaesthesia: numbness in perineum, inner thighs, perianal region (S2-S4)
• Urinary dysfunction: retention (most sensitive early sign) → overflow incontinence
• Bowel dysfunction: constipation → faecal incontinence
• Sexual dysfunction: erectile dysfunction, loss of genital sensation
• Lower back pain: usually present

Signs

• LMN pattern: flaccid weakness (foot drop, ankle dorsiflexion/plantarflexion weakness), reduced/absent ankle reflexes
• Saddle sensory loss: reduced perianal pin-prick sensation
• Reduced anal tone: on PR examination (essential — must be performed)
• Palpable bladder: urinary retention (perform post-void residual scan)

CES Classification

• CES-Suspected (CESS): bilateral radiculopathy ± subjective sphincter disturbance, no objective signs
• CES-Incomplete (CESI): neurogenic urinary retention (>500mL post-void residual), reduced sensation, but some sphincter function preserved → URGENT surgery
• CES-Complete (CESC): painless urinary retention with overflow, faecal incontinence, absent anal tone, saddle anaesthesia → poorer prognosis

Red Flags

• Bilateral leg symptoms + back pain → CES until proven otherwise
• Saddle numbness → CES
• Urinary retention/incontinence with back pain → CES
• Reduced anal tone → CES confirmed clinically

Imaging (Emergency)

• MRI lumbar spine: gold standard; demonstrates cause and level of compression; must be performed URGENTLY (within hours, not days)
• Shows: disc herniation, tumour, abscess, haematoma

Bedside

• Post-void residual bladder volume: catheterise or bladder scan; >500mL supports CES
• PR examination: anal tone, perianal sensation (MUST be documented)
• Neurological examination: bilateral lower limb power, sensation, reflexes

Bloods

• FBC, CRP: if infection suspected
• Coagulation: if haematoma suspected
• PSA, SPEP: if tumour suspected

Surgical (Emergency)

• Emergency surgical decompression: laminectomy ± discectomy
• Timing: ideally within 24-48 hours of onset of CES (CESI — incomplete); earlier is better
• CESC (complete): still operate but prognosis for sphincter recovery is poor

Conservative (if Surgery Inappropriate)

• Catheterisation for urinary retention
• Pain management
• Bowel management
• Rehabilitation

Post-Operative

• Physiotherapy: mobilisation, strengthening
• Continence management: ISC (intermittent self-catheterisation) if bladder function doesn't recover
• Pain management: neuropathic agents (gabapentin, pregabalin)
• Psychology: sexual dysfunction, adaptation

Referral Criteria

• ALL suspected CES: emergency spinal surgery referral
• MRI within hours of clinical suspicion
• Do NOT discharge without definitive assessment if red flags present

CESI decompressed within 48 hours: ~70% recover bladder function. CESC: <30% recover bladder function regardless of timing (but may still improve motor/sensory). Motor recovery: generally better than sphincter recovery. Delayed diagnosis is the strongest predictor of poor outcome and the commonest cause of litigation in spinal surgery. Sexual dysfunction: often persists. Long-term neuropathic pain in ~30-50%.

Cauda Equina vs Conus Medullaris Syndrome

CES Classification and Prognosis