Cauda Equina Syndrome

Cauda equina syndrome: a spinal emergency — recognising the symptoms and acting immediately

⚠⚠ THIS IS A MEDICAL EMERGENCY — Go to A&E immediately if you have:

Sudden difficulty controlling your bladder — inability to urinate or loss of control • Sudden difficulty controlling your bowel — loss of control or loss of sensation • Numbness or altered sensation in the saddle area (between your legs, inner thighs, perineum) • Rapidly worsening weakness in one or both legs • These symptoms alongside back pain or sciatica • Do not wait. Do not sleep on it. Go to A&E now.

Hours
matter — the sooner surgery is performed, the better the outcome for recovery
Bladder
symptoms are the most important — any new urinary difficulty with back pain needs same-day assessment
MRI
is available 24/7 at major centres — investigation is immediate, not next-week

What is cauda equina syndrome?

The cauda equina (Latin for “horse’s tail”) is the bundle of nerve roots at the base of the spinal cord that supplies the bladder, bowel, sexual organs, and lower limbs. When these nerve roots are severely compressed, the result is cauda equina syndrome (CES) — a condition that, if not treated within hours to days, can cause permanent paralysis, loss of bladder and bowel control, and sexual dysfunction.

The most common cause is a large central disc herniation, but CES can also result from spinal stenosis, tumour, infection, haematoma, or trauma. It is rare — affecting approximately 2–6 per 100,000 people per year — but the consequences of delayed treatment are devastating and irreversible.

The symptoms in detail

Bladder dysfunction
The most important symptom. Difficulty starting urination, reduced sensation of fullness, urinary retention (unable to pass urine), or urinary incontinence. Retention is more common than incontinence in CES and may be painless.
Bowel dysfunction
Loss of sensation of needing to defecate, loss of anal tone, or faecal incontinence.
Saddle anaesthesia
Numbness or altered sensation in the perineum, inner thighs, buttocks, and genitals — the area that would contact a saddle. This is a highly specific sign and should always trigger immediate assessment.
Bilateral leg symptoms
Pain, tingling, or weakness in both legs simultaneously. Previous unilateral sciatica that becomes bilateral is particularly concerning.
Sexual dysfunction
Altered genital sensation or inability to achieve erection alongside the other symptoms above.

Incomplete vs complete CES

CES presents on a spectrum. Incomplete CES (CESI) — where bladder and bowel function are impaired but not fully lost — is the critical window for intervention. Complete CES (CESR) with total loss of function carries a poorer prognosis for recovery. This is why acting on early symptoms is so important — CESI can rapidly progress to CESR.

The most common error in CES management

Failure to investigate early bladder symptoms. Many people with urinary difficulty assume it is unrelated to their back pain. Any patient with back pain or sciatica who develops any degree of new urinary difficulty — even mild — should be assessed urgently. If in doubt, go to A&E.

What happens at A&E

  • Urgent MRI of the lumbar spine — the definitive investigation, available 24/7 at major centres
  • Bladder scan — to assess urinary retention
  • Neurological assessment — reflexes, power, and sensation in the lower limbs
  • Emergency surgical decompression — if CES is confirmed, surgery is performed as soon as possible. The sooner surgery is performed, the better the outcome.

↓
Download the Cauda Equina Syndrome Fact SheetPDF — printable summary to share with your GP or practitioner

Related conditions

Disc HerniationThe most common cause of cauda equina syndromeSpinal StenosisAnother potential cause of cauda equina compressionSciaticaNerve root pain — and when it becomes an emergencyAll Back Pain ConditionsBrowse the full condition library