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Cauda Equina Syndrome
Cauda equina syndrome (CES) is a serious medical emergency caused by compression of the nerves at the base of the spinal cord (the “cauda equina”). These nerves control sensation and function in the legs, bladder, bowel and sexual organs.
CES most commonly occurs due to a large slipped (herniated) disc in the lower back, but it can also be caused by spinal stenosis, tumours, infection, bleeding, trauma, or inflammatory conditions.
Urgent diagnosis and treatment are essential. Delay can lead to permanent nerve damage affecting walking, bladder/bowel control and sexual function.
If you suspect cauda equina syndrome, you should seek emergency medical care immediately.
What causes Cauda Equina Syndrome?
CES is caused by pressure on the cauda equina nerves. Causes may include:
- Large lumbar disc herniation (commonest cause)
- Severe spinal stenosis
- Trauma or fracture affecting the lower spine
- Tumour or metastatic spinal disease
- Spinal infection or abscess
- Bleeding around the spine (rare)
- Post-operative complications (rare)
Key symptoms of Cauda Equina Syndrome (Red Flags)
CES can develop suddenly or gradually. Symptoms can vary, but the classic “red flags” include:
Bladder changes
- New difficulty starting to pass urine
- Reduced sensation of bladder filling
- Urinary retention (not being able to pass urine)
- New overflow incontinence (leaking because the bladder is full)
Bowel changes
- New loss of bowel control
- Reduced sensation when opening bowels
- Severe constipation with reduced sensation (in some cases)
Saddle numbness (perineal numbness)
- Numbness or altered sensation around the inner thighs, genitals, buttocks, or the area you would sit on a saddle
Leg symptoms
- New or worsening weakness in one or both legs
- Numbness or pins and needles
- Severe sciatica-type pain (often both legs, but can be one)
- Difficulty walking, stumbling, or legs “giving way”
Sexual function changes
- New erectile dysfunction or loss of sensation
You do not need to have all symptoms for CES to be possible. Any combination of back pain/sciatica plus bladder, bowel, or saddle sensory changes should be treated as an emergency.
Diagnosis
Cauda equina syndrome is diagnosed through urgent clinical assessment and usually requires an emergency MRI scan of the lower spine to identify nerve compression.
A clinician will also assess:
- Leg strength and sensation
- Reflexes
- Saddle sensation
- Bladder function (and may check urine retention)
Treatment
Treatment depends on the cause, but CES most commonly requires urgent spinal surgery to relieve pressure on the nerves (decompression). The aim is to protect nerve function and improve the chance of recovery.
Other treatments may be needed depending on the cause (for example antibiotics for infection or oncology treatment for tumour-related compression), but urgent decompression is the key step when disc compression is the cause.
When to seek urgent help
Call 999 or go to A&E immediately if you have:
- Back pain or sciatica with new bladder problems
- Saddle numbness or altered sensation in the groin/buttocks
- New bowel incontinence or loss of bowel sensation
- New leg weakness or difficulty walking
Do not wait to see if symptoms improve. CES needs emergency assessment the same day.
If you are concerned about possible cauda equina syndrome, seek emergency medical help immediately. If symptoms are urgent but you are unsure, it is safer to treat this as an emergency and be assessed promptly.
16 February 2026