Cauda equina syndrome causes explained

Cauda equina syndrome (CES) happens when the bundle of nerve roots at the bottom of the spinal canal becomes compressed or damaged. These nerves sit below the point where the spinal cord ends and control important functions in the lower body, including movement and sensation in the legs, bladder and bowel function, and sexual function.

The most common cause is a large herniated disc in the lumbar spine, but cauda equina syndrome can also result from spinal stenosis, tumours, spinal trauma, bleeding in the spinal canal, infection or complications following spinal surgery.

CES is a condition which needs to be recognised and treated very quickly. There may have been medical negligence if a doctor or other clinician fails to recognise red flag symptoms, arrange appropriate investigation or act on evidence of serious nerve compression, and that delay causes avoidable harm, resulting in the patient being left with long-term problems.

What is the most common cause of cauda equina syndrome?

A large central disc herniation in the lower back is the most common cause of cauda equina syndrome (CES). A herniated disc, sometimes called a slipped or prolapsed disc, occurs when material from one of the discs between the vertebrae pushes out of its normal position.

Most disc herniations do not cause cauda equina syndrome. CES can develop when a large disc herniation extends into the spinal canal and causes severe compression of multiple cauda equina nerve roots at the same time.

Because these nerve roots provide motor and sensory function to the lower limbs and help control the pelvic organs, significant nerve compression can affect bladder function, bowel function, genital sensation and movement in the legs.

Can L4 and L5 herniation cause cauda equina syndrome?

Yes. A large disc herniation at the L4-L5 level of the lumbar spine can cause cauda equina syndrome if it narrows the spinal canal enough to compress the cauda equina nerve roots. CES can also arise from disc herniation at other lower lumbar levels, including L5-S1.

Doctors need to consider the person's symptoms, neurological findings and imaging, usually including a magnetic resonance imaging (MRI) scan, to establish whether the nerve roots are being compressed.

What other conditions can cause cauda equina syndrome?

Although a herniated disc is the most common cause of CES, several other spinal disorders can place severe pressure on the cauda equina.

Can spinal stenosis cause cauda equina syndrome?

Lumbar spinal stenosis narrows the spinal canal in the lower back, sometimes because of degenerative changes such as arthritis. Severe narrowing can leave too little room for the nerve roots. A herniated disc can cause even greater compression where stenosis is already present.

Can spinal tumours cause cauda equina syndrome?

A tumour can cause cauda equina syndrome if it grows within or close to the spinal canal and compresses the nerve roots. The effect depends on its position, size and the space available around the nerves.

Can a spinal infection or abscess cause cauda equina syndrome?

An infection around the spine can sometimes cause swelling or an abscess. If this develops within or close to the spinal canal, it can reduce the space around the cauda equina and cause serious nerve compression.

Can bleeding in the spinal canal cause cauda equina syndrome?

A spinal haematoma is a collection of blood that can rapidly increase pressure within the spinal canal. Postoperative bleeding can, in uncommon cases, compress the nerve roots and cause cauda equina syndrome.

Can a spinal fracture or serious back injury cause cauda equina syndrome?

A severe lower-back injury can cause CES when a fracture, displaced bone fragment or swelling narrows the spinal canal. This can happen after serious falls or road traffic collisions. New neurological symptoms affecting the legs, bladder, bowel or saddle area require urgent assessment.

Can spinal surgery cause cauda equina syndrome?

Cauda equina syndrome can occur as a rare complication of spinal surgery, including through direct nerve injury or postoperative bleeding that creates new pressure in the spinal canal.

A recognised surgical complication does not automatically mean that medical negligence occurred. The question is whether the surgeon or clinical team provided a reasonable standard of care, whether it was identified quickly enough and whether any failings caused or contributed to the nerve injury.

Can congenital spinal abnormalities cause cauda equina syndrome?

Some people’s bodies have structural differences that reduce the space available within the spinal canal. In rare cases, these abnormalities may contribute to cauda equina compression, either alone or alongside another spinal condition.

The NHS provides further information on conditions that can require lumbar decompression surgery, including cauda equina syndrome.

What are the risk factors for cauda equina syndrome?

A risk factor is not the same as a direct cause. The main cauda equina risk factors are conditions or circumstances that make significant compression within the lumbar spinal canal more likely.

These include:

• Having a large lumbar disc herniation
• Severe spinal stenosis
• A spinal tumour
• Significant trauma to the lower spine
• Having recently undergone a spinal procedure

Some people have more than one factor at the same time; for example, a herniated disc may cause more severe compression where the spinal canal is already narrowed by stenosis.

Cauda equina syndrome can still affect people who do not have an obvious pre-existing risk factor. What matters clinically is whether symptoms suggest that the cauda equina nerves may be compressed and require urgent investigation.

What symptoms can indicate cauda equina syndrome?

The underlying causes differ, but cauda equina compression can produce a recognisable group of red flag symptoms. These include:

• New difficulty starting urination, urinary urgency, reduced sensation when passing urine or urinary retention
• New loss of bladder control or bowel control
• Saddle numbness or altered sensation around the buttocks, genitals and inner thighs
• New sexual dysfunction or reduced genital sensation
• Weakness, numbness or other sensory changes in one or both legs
• Severe lower-back pain or leg pain with neurological symptoms

Cauda equina syndrome is a medical emergency. Anyone with symptoms that could indicate CES should seek urgent medical attention. The North Bristol NHS Trust guidance on cauda equina syndrome explains the bladder, bowel, saddle-area and leg symptoms that require urgent investigation.

For more detail, read our guide to the early symptoms of cauda equina syndrome.

Can you still walk with cauda equina syndrome?

Being able to walk does not rule out cauda equina syndrome. Some people retain mobility while experiencing bladder dysfunction, bowel dysfunction, altered saddle sensation or other neurological symptoms. Doctors should assess the complete pattern of symptoms rather than mobility alone.

How are the causes of cauda equina syndrome diagnosed and treated?

Doctors investigating suspected CES consider the person's medical history, red flag symptoms and findings from a physical examination. Urgent imaging is needed where cauda equina compression is suspected.

Magnetic resonance imaging is commonly used to diagnose cauda equina syndrome. An MRI scan can show the spinal canal, discs and surrounding structures and help identify the cause of the compression. Other imaging tests may sometimes be required.

Confirmed compression commonly requires emergency lumbar decompression surgery to relieve pressure on the nerve roots and prevent further neurological damage. The NHS explains that lumbar decompression surgery may be used where nerves at the base of the spine are compressed by conditions including a slipped disc, spinal stenosis, spinal injury, tumour or abscess.

Recovery varies according to the degree of compression, the functions affected and the treatment required. Read more about the long-term effects of cauda equina syndrome.

When can cauda equina syndrome involve medical negligence?

The condition that causes cauda equina syndrome may develop without anyone being at fault. Medical negligence is a separate question: did the care provided by a GP, emergency doctor, radiologist, surgeon or another clinician fall below a reasonable standard, and did this cause avoidable additional harm?

Examples we may investigate include:

• A GP or hospital doctor failing to recognise reported red flag symptoms
• A failure to carry out an appropriate neurological assessment or arrange urgent referral
• An avoidable delay in arranging an MRI scan where cauda equina compression should have been suspected
• An avoidable delay in reviewing or acting on MRI scan findings
• An avoidable delay in arranging urgent surgical treatment after significant compression has been identified
• Negligent spinal surgery causing direct nerve injury or avoidable postoperative compression

A poor outcome does not by itself prove medical negligence. There must be evidence that the care fell below a reasonable standard and that this caused or materially contributed to additional injury. Our guide to proving medical negligence explains the evidence involved.

How JMW helps with cauda equina medical negligence claims

Our specialist cauda equina syndrome claims team investigates whether avoidable delays or failings in care caused additional nerve damage or worsened the effects of cauda equina syndrome.

We will discuss what happened, the symptoms you reported, the treatment you received and how your daily life has been affected. If we recommend investigating a medical negligence claim, we will obtain relevant GP and hospital records and review the timeline with you.

We will also instruct appropriate independent medical experts where needed. They can assess whether the care was to a reasonable standard and whether any failings caused or contributed to additional harm, including effects on mobility, bladder and bowel function, sexual function or any recognised psychological injury.