Cauda Equina Syndrome


Terminal spinal root compression in the lumbosacral (LS) region, resulting in a constellation of symptoms


Spinal-disc-protrusion-l5Space occupying lesion within lumbar spine canal, including:

  • Disc herniation (most common)
  • Trauma (retropulsion of fracture fragment, dislocation or collapse)
  • Infection/ Haematoma within epidural space
  • Epidural abscess / haematoma
  • Spinal stenosis
  • Tumor


  • Spinal cord
    • Conus medullaris: tapered, terminal end of the spinal cord , ends at T12 or L1 body
    • Filum terminale: non-neural, fibrous extension of the conus medullaris attaching to Cx
    • Cauda equina (horse’s tail): L1-S5 peripheral nerves within the lumbar canal
  • Bladder receives innervation from
      • Parasympathetic nervous system (pelvic splanchnic nerves and the inferior hypogastric plexus)
      • Sympathetic plexus (hypogastric plexus)
    • external sphincter of the bladder is controlled by the pudendal nerve
    • lower motor neuron lesions of cauda equina will interrupt the nerves forming the bladder reflex arcs


Incomplete (CES – I) Complete (CES –R)
Sensorimotor changes (incl. saddle anaesthesia)


altered urinary sensation


Full Urinary/bowel retention/incontinence

Painless urinary retention

(may lead to overflow incontinence)


Faecal incontinence

Clinical presentation:

  • Two distinct clinical presentations: acute (e.g. disc herniation, trauma) and insidious (e.g. spinal stenosis, tumor)
  • Signs & Symptoms
    • Bilateral leg pain
    • Saddle anaesthesia
    • Sensorimotor loss in lower extremity
    • Neurogenic bladder dysfunction (disruption of bladder contraction lead initially to urinary retention and eventually to overflow incontinence
    • Bowel dysfunction is rare

Physical exam:

    • Inspection
      • lower extremity muscle atrophy with insidious presentations (e.g. spinal stenosis)
      • fasiculations are rare
    • Palpation
      • lower back pain/tenderness is not a distinguishing feature
      • palpation of the bladder for urinary retention
    • Neurovascular examination
      • bilateral lower extremity weakness and sensory disturbances
      • decreased or absent lower extremity reflexes
    • Rectal/genital examination
      • reduced or absent sensation to pinprick in the perianal region (S2-S4 dermatomes), perineum, and posterior thigh
      • decreased rectal tone or voluntary contracture
      • diminised or absent anal wink test and a bulbocavernosus reflex


  • AP/lateral plain lumbosacral radiographs: To exclude fracture/dislocation, spondylolisthesis
  • MRI: Study of choice to evaluate neurological compression
  • CT Myelography: If patient unable to undergo MRI



Indications: Significant suspicion of CES, severity of symptoms will increase the urgency for decompression

Technique:  Posterior approach to lumbar spine with surgical decompression of neural elements by way of laminectomy + discectomy

Outcomes: studies have shown improved outcomes in bowel and bladder function and resolution of motor and sensory deficits when decompression performed within 48 hours of the onset of symptoms


Due to delayed presentation or decompression

  • Sexual dysfunction
  • Urinary dysfunction requiring catheterisation
  • Chronic pain
  • Persistent leg weakness


Timing of surgery

Ahn UM, et al. Cauda equine syndrome secondary to lumbar disc herniation: A meta-analysis of surgical outcomes. Spine 2000. 25.1515-1522

The meta-analysis of surgical outcomes of cauda equina syndrome secondary to lumbar disc herniation reviewed 42 studies.

Length of time to surgery was broken down into: < 24 hours, 24-48 hours, 2-10 days, 11 days to 1 month, >1 month.

Preop chronic back pain was associated with poorer outcomes in urinary and rectal function.

Preoperative rectal dysfunction was associated with worsened outcome in urinary continence. Increasing age associated with poorer postop sexual function.

No significant improvement in surgical outcome was identified with intervention < 24 hours from the onset of CES compared with patients treated within 24-48 hours. Similarly, no difference in outcome occurred in patients treated more than 48 hours after the onset of symptoms.

Significant differences, however, were found in resolution of sensory and motor deficits as well as urinary and rectal function in patients treated within 48 hours compared with those treated more than 48 hours after onset of symptoms.

Conclusion of study:  A significant improvement in sensory and motor deficits as well as urinary and rectal function occurred in patients who underwent decompression < 48 hours vs. > 48 hours after the onset of symptoms

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