What Is Cauda Equina Syndrome


Cauda equina syndrome is a rare condition involving compression of nerves in the lumbosacral region of the spine (the lower section of the backbone just before the pelvis). These nerves pass messages between the brain and the lower limbs and pelvic organs. When pinched, the function of these spinal nerves can be affected.1 

The spinal cord begins at the brainstem, runs down through the spinal canal (the bony tunnel formed by the vertebral bones), and stops at the top of the lumbar spine area. At the point where the spinal cord ends, a bundle of nerves and nerve root fibres emerge, descending towards the coccyx (tailbone). This is called the ‘cauda equina’ - Latin for ‘horse’s tail’ - due to its resemblance to a bundle of horse tail hair.1

The nerves of the cauda equina innervate (supply) the legs, perineum (the area between the anus and genitals) and pelvic organs. The messages they send and receive govern sensation and movement in these areas and control bladder, bowel, and sexual function.2 Compression of these nerves can damage them and reduce, or even eliminate, their function. This can cause pain and result in significant neurological deficits.

Causes of cauda equina syndrome

The most common cause of compression in cauda equina syndrome is lumbar disc herniation (also called a lumbar disc prolapse, a disc bulge or a slipped disc), which accounts for 45% of all cases.2 This most frequently occurs at the lumbar spine vertebral levels L4/5 or L5/S1.3 

The spinal column is made up of a series of stacked vertebral bones, with intervertebral discs between each bone. Levels of the spinal column are numbered according to the number order of the vertebral bones. A spinal disc herniation involves damage to the tough, fibrous exterior of an intervertebral disc that allows its soft inner centre to protrude and bulge outwards. This protrusion of the disc can put pressure on components of the nervous system running close by through the spinal canal. In the lower lumbar and sacral regions, the cauda equina nerves run through it. 

In addition to disc herniation, there are a number of other, less common causes of cauda equina compression. These include:2, 4

Signs and symptoms of cauda equina syndrome

Patients with Cauda equina syndrome may experience the following signs and symptoms: 1

  • Lower back pain and leg pain 
  • Tingling, numbness or weakness in the buttocks, back of legs, feet and toes
  • Saddle anaesthesia – numbness of the inner thighs, perineum (area between the anus and scrotum or vulva), buttocks, anal area
  • Changes to bladder and bowel function include:
    • Urinary retention (inability to fully empty the bladder)
    • Urinary incontinence (inability to control the holding of urine and emptying of the bladder, leading to unintentional passing of urine)
    • Loss of sensation of the fullness of the bladder and the awareness of the need to urinate
    • Difficulty initiating urination
    • Bowel incontinence (inability to control bowel movements leading to unintentional leaking of stool) or severe constipation
  • Sexual dysfunction – including impotence (inability to achieve an erection) and loss of sensation in the genital area, or conversely, priapism – defined as a persistent erection in the absence of sexual stimulation
  • Abnormal reflex response 
  • Reduction/loss of (muscle) tone of the anal sphincter


The following techniques are commonly used to diagnose cauda equina syndrome and provide details on the cause, location and extent of the condition:

  • History taking, which includes:
    • Details of symptoms, including duration, pattern, onset
    • Potentially related trauma
    • Previous relevant medical history such as anticoagulation therapy, spinal surgery
  • Physical examination – including sensation, reflexes, stability, ability to carry out specific movements
  • MRI scan (Magnetic Resonance Imaging) – to provide detailed, 3-dimensional images of the spinal cord
  • MyelographyCT (Computerised Tomography) or X-ray after contrast material injection4 to help show areas of pressure on the spinal nerves and nerve roots

Many of the symptoms of cauda equina are also found in other conditions, and these must be excluded through the diagnostic process. 

In particular, lower back/leg pain, altered sensation and muscle weakness can be found in patients with lumbar disc herniation without cauda equina involvement. Lumbar disc disease and herniation are common conditions, and only 2% of these cases result in cauda equina complications.4 

However, the presence of saddle anaesthesia and bladder/bowel control problems alongside symptoms of pain, altered sensation and muscle weakness are strongly indicative of potential cauda equina compression and considered ‘red flags’ (indicators of serious medical conditions). As cauda equina compression constitutes a medical emergency, patients should have these red flag symptoms investigated immediately because the delay of surgical intervention, if it is required, can potentially cause permanent neurological damage and loss of function.

Types of cauda equina syndrome

Cauda equina syndrome can be acute or chronic in nature.4 

Acute symptoms appear suddenly and with severity. Chronic symptoms come on more slowly and gradually, often starting with low back pain and progressing to other symptoms such as changes to bladder function and reduction in bowel control.1

Classification of cauda equina syndrome

Cauda equina syndrome can be classified into:

  • Incomplete cauda equina syndrome (sometimes abbreviated to CESI): involving sensory and motor changes but no complete retention or incontinence of bladder and/or bowel
  • Complete cauda equina syndrome or cauda equina syndrome with true retention (sometimes abbreviated to ‘complete CES’ or CESR): involving sensory and motor changes and full retention or incontinence of bladder and/or bowel4

Management and treatment for cauda equina syndrome

Treatment of cauda equina syndrome aims to remove the pressure on the nerves to allow them to recover and regain their function. This usually requires emergency spinal surgery. The type of surgical decompression technique selected will be decided by the spinal surgeon, depending on the needs of the individual case.

If a  lumbar disc herniation is the cause, a discectomy is commonly recommended. This is a surgical procedure to remove the soft inner section of the disc, which has bulged out of the disc’s fibrous exterior and is putting pressure on the cauda equina nerves.

If appropriate, treatment may also address other causes of the nerve compression, such as cancer, infection or inflammation.

Cauda equina syndrome is considered a medical emergency and should be treated as quickly as possible for the best outcomes. However, even those treated early may still not achieve full recovery from symptoms and may be left with residual numbness, weakness, incontinence or sexual dysfunction. Left untreated, permanent paralysis and loss of bowel, bladder and sexual function can result.1,2


How can I prevent cauda equina syndrome?

Cauda equina syndrome is caused by compression of nerves in the lumbar spine area. The most common cause of this pressure is a herniated lumbar disc. Although disc disease and herniation cannot always be prevented, it may be possible to reduce the risk of their development. Further information on disc herniation and its prevention can be found at the Cleveland Clinic website and the Mayo Clinic website.

How common is cauda equina syndrome?

Cauda equina syndrome is a rare condition, with an estimate of between 0.3 and 7 occurrences in 100,000 people per year (depending on the population group sampled), according to a systematic review carried out in 2020.5

Who is at risk of cauda equina syndrome?

The most common cause of cauda equina syndrome is a herniated lumbar disc. People are at greater risk of developing a lumbar disc herniation as they get older due to the normal processes of degeneration associated with ageing

In addition, the following are also risk factors, according to the Mayo Clinic

  • Having a sedentary lifestyle
  • Being overweight
  • Having a physically demanding job that involves lifting, twisting, pushing, pulling, bending 
  • Smoking 
  • Frequent driving 
  • A genetic predisposition

When should I see a doctor?

Cauda equina syndrome is considered a medical emergency and requires urgent evaluation. The sooner that treatment to decompress the cauda equina nerves is carried out, the better the outcome. If you experience severe pain in the lower back and/or legs along with numbness or weakness in your legs, numbness in your groin/saddle area or changes to your bladder or bowel control, seek urgent advice at a hospital accident and emergency department.


Cauda equina syndrome is a rare condition involving compression of the bundle of nerves located in the lumbar and sacral regions of the spine. This compression can lead to pain, altered sensation and muscle weakness in the legs and pelvic area, sexual dysfunction and loss of bladder and bowel control. Cauda equina syndrome is a medical emergency and requires urgent attention to reduce the risk of long-term complications. Treatment usually involves surgery to reduce compression on the nerves.


  1. Berg EJ, Ashurst JV. Anatomy, back, cauda equina. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Jun 26]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK513251/
  2. Rider LS, Marra EM. Cauda equina and conus medullaris syndromes. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Jun 26]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK537200/
  3. Czervionke LF, Fenton DS. Imaging painful spine disorders e-book. Elsevier Health Sciences; 2011. 667 p. Available at: https://books.google.fr/books?hl=en&lr=&id=TavGrbK6lWoC&oi=fnd&pg=PP1&dq=Cauda+Equina+Syndrome+Douglas+S.+Fenton+M.D.,+in+Imaging+Painful+Spine+Disorders,+2011&ots=gj96nV1ND4&sig=2A41gfMA4rvh8PkmJlDtaNCwaIU&redir_esc=y#v=onepage&q=Cauda%20 Equina%20Syndrome%20 Douglas%20S.%20 Fenton%20M.D.%2C%20in%20Imaging%20 Painful%20skin%20 Disorders%2C%202011 &f=false
  4. Gitelman A, Hishmeh S, Morelli BN, Joseph SA, Casden A, Kuflik P, et al. Cauda equina syndrome: a comprehensive review. Am J Orthop (Belle Mead NJ). 2008 Nov;37(11):556–62. Available from: https://cdn.mdedge.com/files/s3fs-public/Document/September-2017/037110556.pdf
  5. Hoeritzauer I, Wood M, Copley PC, Demetriades AK, Woodfield J. What is the incidence of cauda equina syndrome? A systematic review. Journal of Neurosurgery: Spine [Internet]. 2020 Feb 14 [cited 2023 Jun 26];32(6):832–41. Available from: https://thejns.org/spine/view/journals/j-neurosurg-spine/32/6/article-p832.xml
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

Get our health newsletter

Get daily health and wellness advice from our medical team.
Your privacy is important to us. Any information you provide to this website may be placed by us on our servers. If you do not agree do not provide the information.

Susannah Hollywood

Health Writer – Physiotherapist – MSc in Health Ergonomics

Susannah is a freelance Health Writer who produces high quality information on health topics for lay audiences. She is passionate about increasing health literacy to improve health outcomes.

Susannah has had extensive involvement with patients throughout her varied career as a Healthcare Professional. Through this experience, she has developed a deep understanding of individuals’ needs at different points in their health journeys.

Incorporating this insight and empathy into her writing, Susannah strives to provide accurate, succinct and unambiguous information on health topics. She takes care to select the appropriate terminology, level of detail and tone for each piece.

Susannah has broad experience of writing in the field of healthcare for a variety of lay audiences. This includes online health information articles, news articles, reports, grant applications, training manuals and patient information leaflets.

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
Klarity / Managed Self Ltd
Alum House
5 Alum Chine Road
Westbourne Bournemouth BH4 8DT
VAT Number: 362 5758 74
Company Number: 10696687

Phone Number:

 +44 20 3239 9818