Cauda Equina Syndrome

Definition: Syndrome characterized by dysfunction of multiple lumbar and sacral nerve roots in the lumbar vertebral canal due to compression

Anatomy

• The spinal cord terminates in the conus medullaris at the T12/L1 vertebral body in adults
• Cauda equina
  • Collection of nerve roots from L1-S5
  • Compression from various causes results in lower motor neuron pathology

Compressive Causes:

• 

  

  Disc herniation (most common cause)

• Epidural abscess
• Spinal epidural hematoma
• Diskitis
• Tumor (metastatic or primary CNS)
• Trauma (retropulsion of fracture fragment)
• Spinal stenosis

Presentation (Lavy 2009):

• Symptoms may develop acutely or progressively over time
• Symptoms
  • Back pain
  • Sciatica
    • Seen in up to 97% of patients (Korse 2017)
    • Bilateral leg pain and/or weakness common
  • Change in sensation in the lower extremities
  • Bladder dysfunction (retention and/or incontinence) – up to 92% (Korse 2017)
    • Disruption of autonomic innervation leads to retention and overflow incontinence
  • Bowel dysfunction (constipation and/or incontinence) – up to 74% (Korse 2017)
  • Decreased sensation in the perianal area – up to 93% (Korse 2017)
  • Sexual dysfunction (i.e. impotence)
• Physical Exam

  • 

    Lower extremity weakness, numbness or paresthesias (usually bilateral)

  • Decreased or absent lower extremity reflexes
  • Hypotonia/atrophy of the lower extremities (in chronic presentations)
  • Urinary retention (increased post void residual)
  • Saddle anesthesia: Reduced or absent sensation in the perineal area (S2-S4 innervation)
  • Decreased or absent rectal tone

Differential Diagnosis (non-compressive causes of spinal cord dysfunction)

• Multiple Sclerosis
• Transverse Myelitis
• Myelopathies (e.g. HIV related)
• Spinal cord infarction
• Spinal AVM
• Syringomyelia

ED Evaluation and Management:

• Imaging
  • Bladder US
    • Normal post-void residual (PVR) < 50 ml (may be up to 100 ml in patients > 65 years)
    • PVR = 0.5 X AP diameter X lateral diameter X sagittal diameter of the bladder
  • Plain X-rays and CT scans can show bone and soft tissue abnormalities but not spinal cord abnormalities
  • CT Myelogram
    • Allows for visualization of the spinal cord and associated abnormalities
    • Requires spinal tap followed by injection of contrast. This limits it’s utility
    • Can be used for patients who have contraindications for MRI or when MRI unavailable
  • MRI
    • Imaging modality of choice for cauda equine syndrome
    • Image types: Obtain sagittal and axial T1 and T2 sequences
• Neurosurgical or orthopedic consultation for emergency surgery
  • Surgery should be performed within 24 hours to increase the chance of better outcomes (Todd 2005)
  • The presence of urinary retention/incontinence at presentation is a predictor of poor outcomes

Take Home Points

• Cauda equina syndrome is a rare emergency with devastating consequences
• Early recognition is paramount as the presence of bladder dysfunction portends bad functional outcomes
• The presence of bilateral lower extremity weakness or sensory changes should alert clinicians to the diagnosis. Saddle anesthesia (or change in sensation) and any bladder/bowel changes in function should also raise suspicion for the disorder
• MRI is the diagnostic modality of choice though CT myelogram can be performed if necessary
• Prompt surgical consultation is mandatory for all patients with cauda equina syndrome regardless of symptoms at presentation

For More on This Topic Checkout:

• EM Cases: Best Case Ever 11: Cauda Equina Syndrome
• OrthoBullets: Cauda Equina Syndrome
• Radiopaedia: Cauda Equina Syndrome

References:

1. Lavy C et al. Cauda Equina Syndrome. BMJ 2009; 338: PMID: 19336488
2. Todd NV. Cauda equina syndrome: the timing of surgery probably does influence outcome. Br J Neurosurg 2005;19:301-6 PMID: 16455534
3. Korse NS et al. Cauda Equina Syndrome: presentation, outcome and predictors with focus on micturition, defecation and sexual dysfunction. Eur Spine J 2017; 26(3): 894-904. PMID: 28102451
4. Perron AD, Huff JS: Spinal Cord Disorders, in Marx JA, Hockberger RS, Walls RM, et al (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, ed 8. St. Louis, Mosby, Inc., 2010, (Ch) 106: p 1419-30.

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)

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