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What is the cauda equina?

The lower end of the spinal cord is at the level of the first or second lumbar bone (vertebra). The nerves from the spinal cord then form a structure called the conus medullaris. The spinal nerves continue to branch out below the conus medullaris to form the cauda equina.

The corda equina carries nerves which control the bladder and bowel. The cauda equina also carries nerves which control movement of the legs, and nerves which sense light touch and pain in the legs or around the back passage (perineum).

Cauda equina syndrome (CES) is a particularly serious type of nerve root problem. There is pressure on the nerves at the very bottom of the spinal cord. The pressure on the nerves stops the nerves from working properly. If the pressure is not treated quickly then CES may cause permanent nerve damage.

What causes cauda equina syndrome?

The most common cause of CES is a prolapsed disc (often called a 'slipped disc'). Other much rarer causes include infection and bone cancer.

CES is rare. It occurs mainly in adults but can occur at any age. Around 3 people per every 100,000 people develop it every year.

The symptoms of CES usually start suddenly and progress quickly. Occasionally the symptoms start slowly. CES may cause low back pain but not all people with CES have back pain.

The symptoms of cauda equina syndrome include pain radiating down one or both legs and/or severe low back pain with:

• Numbness or weakness in both legs.

• Loss of feeling pins and needles between your inner thighs or genitals.

• Numbness in or around your back passage or buttocks.

• Altered feeling when using toilet paper to wipe yourself.

• Increasing difficulty when you try to pass urine.

• Increasing difficulty when you try to stop or control your flow of urine.

• Loss of sensation when you pass urine.

• Leaking urine or a need to use pads.

• Not knowing when your bladder is either full or empty.

• Inability to stop a bowel movement or leaking.

• Loss of sensation when you pass a bowel motion.

• Change in ability to achieve an erection or ejaculate.

• Loss of sensation in genitals during sexual intercourse.

If you experience any of these symptoms then you should seek medical help immediately.

CES is mainly suspected on the symptoms and, sometimes, also by a doctor's examination. The diagnosis of CES then requires an emergency scan in hospital. Therefore, anyone with possible CES should be seen urgently in hospital.

Investigations usually include an MRI scan to confirm the diagnosis. Other investigations may include a CT scan and tests of bladder control.

Urgent surgery is often but not always needed to relieve the pressure on the nerves and prevent permanent nerve damage.

The treatment otherwise depends on the cause of CES - for example, for infection, antibiotic medicines. Radiotherapy may be used if CES has been caused by bone cancer.

The outlook (prognosis) depends on the cause of CES and how quickly treatment can be provided.

Recovery of cauda equina syndrome after spinal decompression surgery is a gradual process that can take weeks or months for the nerves to heal.

A delay in diagnosis and effective treatment increases the risk of long-term bladder, bowel and sexual problems. Late diagnosis and a delay in treatment can also increase the risk of a permanent nerve damage affecting the bladder, bowel and legs.

The lower back is also called the lumbosacral area of the back. It is the part of the back between the bottom of the ribs and the top of the legs.

Most of the lower back is made up from muscles that attach to, and surround, the spine. The spine is made up of many bones called vertebrae. The vertebrae are roughly circular and between each vertebra is a disc.

The discs between the vertebrae are a combination of a strong fibrous outer layer and a softer, gel-like centre. The discs act as shock absorbers and allow the spine to be flexible.

Close-up view

Strong ligaments also attach to nearby (adjacent) vertebrae to give extra support and strength to the spine. The various muscles that are attached to the spine enable the spine to bend and move in various ways.

The spinal cord, which contains the nerve pathways to and from the brain, is protected by the spine. Nerves from the spinal cord come out from between the vertebrae to take and receive messages to various parts of the body.