Cauda Equina Syndrome: Patient Information

What is cauda equina syndrome?

Cauda equina syndrome (CES) is a rare but serious condition where the bundle of nerves at the very bottom of your spinal cord, called the cauda equina, becomes squeezed or compressed. These nerves control your legs, bladder, bowel and sexual function, so if the pressure isn't relieved quickly, it can cause permanent damage.

Symptoms of cauda equina syndrome

CES causes a specific pattern of warning signs, alongside back pain and/or pain going down one or both legs. Symptoms usually start suddenly and get worse quickly, though occasionally they build up gradually. Not everyone with CES has back pain. Watch out for:

• numbness or weakness in both legs, for example difficulty lifting your foot upwards or straightening your leg
• numbness, or pins and needles, around your back passage, buttocks, genitals or inner thighs, sometimes called 'saddle' numbness, because it covers the area that would touch a saddle
• altered feeling when you wipe yourself after using the toilet
• increasing difficulty passing urine, or controlling the flow once you start
• not being able to tell when your bladder is full or empty
• leaking urine, or a sudden need to use pads
• loss of sensation when you pass urine or empty your bowels
• being unable to stop a bowel movement, or bowel leaking
• a change in your ability to get or keep an erection, or to ejaculate
• loss of sensation in your genitals during sex.

Causes and who is at risk

CES is very rare, affecting around 1 to 3 people in every 100,000 each year. It usually happens to adults of working age, though it can occur at any age.

The most common cause is a sudden, large disc prolapse (sometimes called a slipped disc) in your lower back, pressing on the nerves. If you have a naturally narrow spinal canal, even a moderate disc prolapse can be enough to cause CES. Less common causes include a tumour, infection, or injury to the spine.

If you've already had sudden sciatic pain in both legs, this can be a sign that you're at greater risk of developing CES.

Are there different types of cauda equina syndrome?

CES itself isn't usually divided into separate named types, but it can develop in different ways. Most often, symptoms start suddenly and get rapidly worse, within hours or days. In some people, though, symptoms build up more gradually over a longer period. Either pattern needs the same urgent assessment.

How is cauda equina syndrome diagnosed?

CES is initially suspected based on your symptoms and a physical examination. This may include testing the feeling in your legs and around your back passage with a pin-prick test, checking your reflexes and leg muscle strength, checking the tone of the muscle around your back passage, and sometimes an ultrasound scan of your bladder to see how much urine is left after you empty it.

The only way to confirm or rule out CES is an emergency MRI scan of your spine, carried out in hospital. If an MRI isn't possible for any reason, another type of scan will be arranged instead. Reassuringly, in around 9 out of 10 people who are assessed for CES symptoms, the scan rules it out.

How is cauda equina syndrome treated?

If CES is confirmed, urgent surgery is needed in most cases, to relieve the pressure on the nerves and help prevent permanent damage. It's very important that this isn't delayed. Surgery is associated with better outcomes the sooner it's carried out, particularly within 24 hours of your symptoms starting.

The aim of surgery is to preserve whatever nerve function you still have at the time of the operation. There's a good chance it will help with your leg pain, and some scope for your nerve function to improve, though this can't be guaranteed.

As with any operation, there are risks, including a small chance of making things worse, such as paralysis in your legs, complete loss of bladder or bowel function, or sexual difficulties including being unable to get an erection. Your surgical team will talk through these risks with you before you decide together on the best way forward.

If CES is caused by something other than a disc prolapse, treatment will target that instead, for example antibiotics for an infection, or radiotherapy if it's caused by a bone tumour.

When should I see a doctor?

CES is a medical emergency. If you notice any of the warning signs above, especially new bladder, bowel or sexual symptoms alongside back or leg pain, go to your nearest A&E straight away. Don't wait to see if things improve on their own, and don't feel embarrassed about describing bladder, bowel or sexual symptoms – healthcare professionals are used to discussing them and will treat you with sensitivity.

Timing genuinely matters: the longer the nerves stay under pressure, the more damage can occur, so getting checked quickly gives you the best chance of a good recovery.