Cauda Equina Syndrome (CES)

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Annually, cauda equina syndrome (CES) is believed to newly affect between 1 person per 33,000- 100,000.1 Patient gender, age and race are not thought to influence rates of CES; however small caseloads may limit insight into such relationships. Regardless of the epidemiology, CES is a spinal emergency necessitating quick and effective care to mitigate permanent neurological sequelae. The disease itself affects the tail end of the spinal cord- the cauda equina. When this anatomy (below) is disrupted, a characteristic collection of symptoms emerge and must be urgently investigated to rule out CES. Despite the need for tertiary management, patients usually present acutely to primary care. It is therefore crucial for all health professionals to be familiar with the features of CES.


Figure 1. The Cauda Equina Syndrome UK Charity provides support, education and practical advice to individuals affected by CES and their families in the U.K. More info can be found here.

Anatomy of the Lower Spinal Cord

The spine is broadly categorized into 5 segments: cervical, thoracic, lumbar, sacral and coccygeal. Each segment contains a series of vertebrae that can be numbered systematically for easy recognition of structures pertaining to these bony landmarks (C1-7, T1-12, L1-5, S1-5). The spinal cord is a bundle of nerve fibres which run centrally through the vertebral canal. This ordered fashion of fibres begins to taper and terminate at the conus medullaris. In adults, this is usually found at the L2 vertebral level. Inferior to this point situates a bundle of spinal nerve roots, referred to as the cauda equina or “horse’s tail” of the spinal cord. Below, the filum terminale marks the end of the spinal meninges at S2.

Check out our spinal cord anatomy article to learn more.


Cauda equina
Figure 2. A dissection with reflection of the dura mater and identification of the conus medullaris (1), filum terminale (2) and cauda equina (3). Note the similarity of the cauda equina to a horse’s tail for which it is named. 10


The aetiology of cauda equina syndrome can be thought of as any factor which compresses the spinal nerve roots.2

  • Lumbar disc herniation- most commonly L4/5, L5/S1 levels. This may be secondary to degenerative disc disease, trauma, or infection
  • Spinal vertebral fractures or subluxation
  • Malignancy- primary or metastatic. Breast, prostate and lung cancer most commonly metastasize to the spine.
  • Spinal infection- abscess, meningitis, TB/Pott’s disease
  • Iatrogenic- spinal anaesthesia, post-op haematoma, manipulation

History and Examination

Diagnosis of CES relies heavily on rapid recognition of characteristic features of the syndrome. A thorough neurological history and examination are essential in order to elicit these symptoms and signs.


Depending on the patient’s presenting complaint, neurological history-taking should be tailored towards identifying and ruling out the ‘red-flags’ of CES.1,3 Broadly, a useful structure is as follows:


  • Patient name, DOB
  • Your name, role
  • Consent for history-taking

Presenting Complaint

Patients may present with back pain, as well as pain, paraesthesia and numbness in the distributions of any lumbar or sacral dermatomes. Some cases may present following trauma or episodes of mechanical stress. All such patients should be screened for red flag symptoms of possible CES.

Red flags that point towards CES include:

  • Bilateral sciatica
  • Saddle anaesthesia
  • Bowel/bladder dysfunction- most commonly urinary retention 4
  • Sexual dysfunction

History of Presenting Complaint

  • Onset/Duration- CES symptoms often present acutely or sub-acutely
  • Progression- symptoms may be worsening
  • SOCRATES for pain- usually low back, quick onset, sharp pain, sometimes radiating to leg or hip, associated with bladder/bowel dysfunction, very severe

Ask about features which may point to the underlying cause of CES:

  • Stenosis: Pain relief on bending forward/sitting
  • Malignancy: Fevers, night sweats, unexplained weight loss
  • Infection: Fevers, night sweats, vaccinations (meningitis), recent travel (TB), local sources of infection
  • Iatrogenic: Recent surgery, localised collection of fluid around the lumbar spine (haematoma)

Past Medical History

  • Recent trauma/heavy lifting
  • Previous hospitalisations
  • Previous surgeries, including spinal operations


  • It is important to ask about anticoagulation in preparation for surgical management of CES

Family History

  • Rheumatological disease
  • Degenerative disc disease
  • Osteoporosis
  • Cardiovascular disease
  • Malignancy

Social History

  • Smoking, alcohol, recreational drug use
  • Occupation- important to understand the potential consequence on work

Ideas, Concerns, Expectations (ICE)

Patients may not be familiar with CES, therefore it is important to explain your clinical suspicion and the role of MRI for further investigation.


Following a thorough patient history, examination is necessary to identify the severity of sacral dysfunction if patients are complaining of red flag symptoms. Where patients are not symptomatic of clear red flag symptoms, but a history with suspicious features is present (i.e. sudden onset back pain or sciatica, rapidly worsening back pain or sciatica, or symptoms related to a possible primary cause of CES), examination is necessary to identify or rule out evidence of CES.

The following should be carried out:

Lower Limb Neurological Examination

In the case of CES, clinical examination will elicit signs of lower motor neuron dysfunction:

  • Tone- hypotonia
  • Power- bilateral or unilateral weakness
  • Reflexes- areflexia
  • Sensation- abnormal sensory changes
    • See the Geeky Medics guide here

Digital Rectal Examination

To assess for:

  • Saddle anaesthesia (loss of perianal sharp/crude touch discrimination)
  • ↓ perineal sensation
  • ↓ anal sphincter tone/loss of anal squeeze
  • Regardless of embarrassment, perianal pinprick discrimination should be assessed to rule out sensory dysfunction
    • See the Geeky Medics guide here

Abdominal Examination (brief)

  • To assess for palpable bladder- urinary retention
    • See the Geeky Medics guide here

Classification of CES

Based on clinical features, CES may be broadly categorized into incomplete vs. complete pathology. Patients with incomplete CES will complain about urinary difficulties, altered urinary sensation, loss of desire to void, hesitancy and urgency. Patients with complete CES demonstrate definitive urinary retention with associated overflow incontinence. Both classifications require urgent further investigation.


Most importantly, suspected CES should prompt urgent surgical referral to an appropriately equipped centre.2 Meanwhile, the following investigations should be sought:5

  • MRI Spine – ideally within 1 hour of the patient presenting, with T2 weighted sequences. The Society of British Neurological Surgeons (SBNS) and British Association of Spine Surgeons recommend that there be no hesitation in attaining an MRI for patients with suspected CES. This may be done at the nearest local centre, prior to engaging in discussions with the spinal surgery team. The MRI should be prioritized above elective cases.6 A CT myelogram may be used in situations whereby MRI is contraindicated.
  • Post-void residual volume (PVR) – to assess for urinary retention



Patients with suspected CES should be formally assessed using the ABCDE method. Once the patient is stable, adequate analgesia should be prescribed. If urinary retention is present, a catheter should be inserted prior to transfer to neurosurgery. Sacral observations should be undertaken frequently.

If a reversible cause of CES can be ascertained from MRI, then urgent surgical decompression should be offered. Decompression may include a laminectomy (removal of vertebral lamina), discectomy (removal of intervertebral disc) or both, as well as removal of any other compressive lesions. Specific surgical approaches will depend on the underlying pathology:

  • Lumbar disc herniation: Laminectomy +/- discectomy
  • Spinal stenosis: Laminectomy
  • Spinal trauma: Depends on mechanism and nature of injury
  • Malignancy: Surgical excision +/- decompression (laminectomy or discectomy)
  • Spinal Abscess/empyema: Laminectomy, evacuation of abscess +/- discectomy and antibiotics as per local protocol

*Timing of surgery for CES can be controversial. For patients presenting during the evening/night-time, some neurosurgeons argue there is no benefit in urgent surgical intervention for complete CES, and such cases may be done in the morning. This is largely due to poor prognostic factors. However, ethical considerations prohibit the investigation of such hypotheses with upper-tiered research methods.2

QUICK REVIEW of Vertebral Anatomy

Spinal vertebrae
Figure 4. Anatomy and relationships of the spinal vertebrae. 9 Note the lamina and the intervertebral disc- two structures commonly removed during surgical decompression of the spinal cord



CES is a spinal emergency and requires urgent surgical management or long term neurological sequelae are likely to be permanent. Examples include:

  • Paraplegia
  • Lower limb numbness
  • Chronic urinary retention or incontinence
  • Chronic sexual dysfunction

Poor prognostic factors include: age, gender, duration of complaints of herniated disc, duration of CES complaints, time to decompression, saddle anaesthesia, bowel/urinary dysfunction.3

CES Snapshot

What is it?

Disruption of cauda equina


Disc herniation, stenosis, trauma, malignancy, abscess


Sciatica, altered perineal sensation, bladder/bowel dysfunction


Lower Limb Neurological Examination, Digital Rectal Examination, Post-residual Volume, MRI Spine


ABCDE, analgesia, catheter if retention, urgent surgical decompression (laminectomy +/- discectomy)




  1. Gardner A, Gardner E, Morley T. Cauda equina syndrome : a review of the current clinical and medico-legal position. 2011;690–7.
  2. Lavy C, James A, Wilson-macdonald J, Fairbank J. Cauda equina syndrome. 2009;338(April).
  3. Korse NS, Pijpers JA, Zwet E Van, Elzevier HW. Cauda Equina Syndrome : presentation, outcome, and predictors with focus on micturition, defecation , and sexual dysfunction. 2017;894–904.
  4. Fraser S, Roberts L, Murphy E, S AF, Roberts L, Cauda ME. Cauda Equina Syndrome : A Literature Review of Its Definition and Clinical Presentation. YAPMR [Internet]. 2009;90(11):1964–8. Available from: [LINK]
  5. Rider IS ME. Cauda Equina And Conus Medullaris Syndromes. [Internet]. StatPearls Publishing. 2019 [cited 2019 Jul 1]. Available from: [LINK]
  6. Standards of Care for Investigation and Management of Cauda Equina Syndrome. :2018.
  7. Mostafa El-Feky HK. Cauda equina syndrome [Internet]. Radiopedia. 2019 [cited 2019 Jul 1]. Available from: [LINK]
  8. Jing Jing Chan JJO. A rare case of multiple spinal epidural abscesses and cauda equina syndrome presenting to the emergency department following acupuncture. Int J Emerg Med [Internet]. 2016;9(1). Available from: [LINK]
  9. Jmarchn. Posterolateral view of vertebrae, labelled description [Internet]. Wikimedia. 2015 [cited 2019 Jul 2]. Available from: [LINK]
  10. John A Beal, PhD Dep of Cellular Biology & Anatomy, Louisiana State University Health Sciences Center Shreveport [CC BY 2.5 (]. Available from: [LINK]


James Loan

Neurosurgery Registrar


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