A plain-English guide
What is Cauda Equina Syndrome?
Cauda Equina Syndrome — CES — happens when the bundle of nerves at the very bottom of the spinal cord becomes severely compressed. It is rare. It is also a medical emergency.
When something — most often a slipped disc — pushes hard against these nerves, they stop working properly. The result can be intense lower-back pain, weakness or numbness in the legs, numbness around the buttocks and genitals (the “saddle area”), and a sudden loss of bladder or bowel control.
Without urgent treatment, the damage can be permanent. That is why doctors describe CES as a surgical emergency — every hour matters. Most patients need an emergency MRI scan and, if CES is confirmed, decompression surgery — ideally within 48 hours of symptoms starting.
CES is uncommon: roughly three people in every 100,000 are affected each year. It can happen at any age, but it’s most often seen in adults. Because it’s rare, it’s also easily missed — which is why awareness matters so much.
CES is not just “a bad back”. It is a sudden, serious loss of nerve function — and recognising the signs early can be the difference between recovery and lifelong disability.
What causes it?
The most common cause is a herniated lumbar disc — a slipped disc in the lower spine that bulges back into the spinal canal and presses on the nerves. If someone’s spinal canal is already narrow (often from age-related changes), even a moderate disc problem can be enough to trigger CES.
Other causes are less common but important to know about:
- Spinal stenosis — gradual narrowing of the spinal canal, often from arthritis or thickened ligaments.
- Tumours in the lower spine, which can grow large enough to compress the nerves.
- Infection — for example an epidural abscess — which can swell and squeeze the nerves.
- Trauma — a fracture, fall or car accident causing bleeding or bone displacement around the spine.
- Surgical complications — rarely, bleeding or swelling after lumbar surgery or spinal anaesthetic.
- Vascular or congenital problems — such as a spinal arteriovenous malformation, or a narrow canal someone is born with.
These causes often overlap. An older person with arthritis may have a tighter spinal canal to begin with, which means a sudden disc problem is more likely to tip into CES.
Why every hour counts
The nerves of the cauda equina control some of the most fundamental things our bodies do — walking, going to the toilet, feeling our own skin. Once those nerves are damaged, the recovery window narrows quickly. Surgery within roughly 48 hours of the first warning signs gives the best chance of full recovery.
That’s why we tell people, and their families, and their GPs: if you suspect CES, don’t wait. Go straight to A&E and say the words “I’m worried about cauda equina syndrome.”