Cauda Equina Syndrome (CES)

Introduction

Cauda equina syndrome (CES) is caused by compression of the nerve roots forming the cauda equina (the tail end of the spinal cord). CES produces a characteristic set of clinical features and is a surgical emergency requiring urgent intervention to prevent permanent neurological deficits.¹

Annually, cauda equina syndrome (CES) is believed to newly affect between 1 person per 33,000- 100,000.¹ 

Aetiology

Anatomy

The spine is divided into five 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.

For more information, see our spinal cord anatomy overview.

Causes of cauda equina syndrome

The aetiology of cauda equina syndrome can be thought of as any pathology which compresses the spinal nerve roots:³

• 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 metastasise to the spine.
• Spinal infection: abscess, meningitis, tuberculosis/Pott’s disease
• Iatrogenic: spinal anaesthesia, post-operative haematoma, manipulation

Clinical features

History

Typical symptoms of cauda equina syndrome may include:^1,3,4

• Severe back pain
• Bilateral sciatica
• Perianal (‘saddle’) anaesthesia
• Bowel and bladder dysfunction: most commonly urinary retention
• Sexual dysfunction

Other important areas to cover in the history include:^1,3,4

• Past medical history: history of spinal pathology or malignancy
• Past surgical history: spinal operations
• Social history: occupation and functional status

Clinical examination

All patients with suspected CES require a thorough lower limb neurological examination and rectal examination.

Lower limb neurological examination

Typical clinical findings on lower limb examination include lower motor neuron signs such as:

• Tone: hypotonia
• Power: bilateral or unilateral weakness
• Reflexes: areflexia
• Sensation: abnormal sensory changes

Rectal examination

Typical clinical findings on rectal examination may include:

• Saddle anaesthesia (loss of perianal sharp/crude touch discrimination)
• Reduced perineal sensation
• Reduced anal sphincter tone/loss of anal squeeze

Abdominal examination

A brief abdominal examination should be performed to assess for a palpable bladder (indicative of urinary retention).

Classification of CES

Based on clinical features, CES may be broadly categorised into incomplete or 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.

Investigations

The most important investigation for patients with suspected cauda equina syndrome is an MRI spine. The Society of British Neurological Surgeons (SBNS) and the British Association of Spine Surgeons recommend MRI should be performed as soon as possible, prior to discussion with spinal surgeons.⁶ A CT myelogram may be considered situations whereby MRI is contraindicated.

Management

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

All patients should be discussed with neurosurgery, following local guidelines. Emergency transfer to a specialist spinal centre may be required depending on neurosurgical advice. 

Surgical management

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 the intervertebral disc) or both, as well as the 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 the mechanism and nature of the injury
• Malignancy: surgical excision +/- decompression (laminectomy or discectomy)
• Spinal abscess/empyema: laminectomy, evacuation of abscess +/- discectomy and antibiotics as per local protocol

The 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 performed the next day (this is due to poor prognostic factors). However, ethical considerations prohibit the investigation of such hypotheses with upper-tiered research methods.²

Complications

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

Complications of CES may include:

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

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

Key points

• Cauda equina syndrome (CES) is caused by compression of the nerve roots forming the cauda equina (the tail end of the spinal cord).
• The aetiology of cauda equina syndrome can be thought of as any pathology which compresses the spinal nerve roots.
• All patients with back pain should be assessed for ‘red flag’ features suggestive of cauda equina syndrome.
• Red flag features suggestive of cauda equina include bilateral sciatica, severe/progressive neurological deficit of the legs, difficulty initiating micturition, urinary incontinence, faecal incontinence, saddle anaesthesia and laxity of the anal sphincter.
• Based on clinical features, CES may be broadly categorised into incomplete or complete pathology.
• The most important investigation for patients with suspected cauda equina syndrome is an MRI spine.
• All patients should be discussed with neurosurgery, following local guidelines. Emergency transfer to a specialist spinal centre may be required depending on neurosurgical advice. 
• CES is a spinal emergency and requires urgent surgical management or long-term neurological sequelae are likely to be permanent.

Reviewer

James Loan

Neurosurgery Registrar

Editor

Dr Chris Jefferies

References

1. Gardner A, Gardner E, Morley T. Cauda equina syndrome: a review of the current clinical and medico-legal position. 2011;690–7.
2. John A Beal. Human caudal spinal cord – Anterior view. License: [CC-BY]
3. Lavy C, James A, Wilson-macdonald J, Fairbank J. Cauda equina syndrome. 2009;338(April).
4. 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.
5. 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]
6. Rider IS ME. Cauda Equina And Conus Medullaris Syndromes. [Internet]. StatPearls Publishing. 2019 [cited 2019 Jul 1]. Available from: [LINK]
7. Standards of Care for Investigation and Management of Cauda Equina Syndrome. :2018.
8. Mostafa El-Feky HK. Cauda equina syndrome [Internet]. Radiopedia. 2019 [cited 2019 Jul 1]. Available from: [LINK]
9. 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]