Definition
Compression of the lumbosacral nerve roots below the conus medullaris that disturbs bladder, bowel, sexual and perineal sensory function. A surgical emergency.
Aetiology
- Central lumbar disc herniation, most often at L4 to L5 and L5 to S1
- Severe central lumbar canal stenosis, including spondylolisthesis
- Tumour, epidural abscess or epidural haematoma
- Fracture and trauma
Classification
Cauda equina syndrome
| Type | Features |
|---|---|
| CES-I (incomplete) | Altered urinary sensation, reduced desire to void or a poor stream, without retention |
| CES-R (retention) | Painless urinary retention with overflow incontinence. Poorest prognosis |
Original publication Gleave JR, Macfarlane R. Cauda equina syndrome: what is the relationship between timing of surgery and outcome? Br J Neurosurg. 2002;16(4):325-8.
Clinical Features
- Bilateral or alternating leg pain
- Saddle (perianal and perineal) numbness
- Reduced bladder sensation, hesitancy or retention
- Reduced anal tone and altered bowel control
- Sexual dysfunction
- Lower motor neurone weakness and reflex loss in the legs
Investigations
- Urgent MRI of the lumbosacral spine. Image the whole spine if the cause is not explained
- Bladder scan for post void residual volume
- Document anal tone and perianal sensation before surgery
Management
- Decompression. Urgent laminectomy and discectomy for a herniated disc, without waiting for retention to develop
- Timing. A meta-analysis of 322 patients found better sensory, motor, bladder and bowel recovery with decompression within 48 hours than after 48 hours. No difference between under 24 hours and 24 to 48 hours
- Non-disc causes. Treat the cause, with antibiotics for abscess and radiotherapy or surgery for tumour
Prognosis
- Bladder, bowel and sexual dysfunction can persist after decompression
- Retention at presentation (CES-R) predicts poorer bladder recovery
References
Ahn UM, Ahn NU, Buchowski JM, Garrett ES, Sieber AN, Kostuik JP. Cauda equina syndrome secondary to lumbar disc herniation: a meta-analysis of surgical outcomes. Spine (Phila Pa 1976). 2000, 25(12), 1515-22. PubMed
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 21 October 2026.